This PDF file contains the front matter associated with SPIE Proceedings Volume 11200, including the Title Page, Copyright information, Table of Contents, Author and Conference Committee lists.

We report on the experimental and numerical results for the second-harmonic generation spectroscopy by doughnut-shaped cylindrical vector beams of azimuthal and radial polarizations in individual subwavelength AlGaAs particles, which support multipolar Mie resonances at the fundamental and double frequencies. We observe high-Q resonant optical modes associated with bound states in the continuum for the azimuthally polarized pump beam with the record-high efficiency (0.1%) of the up-conversion nonlinear optical process due to a strong electromagnetic field confinement. Our findings provide an important step towards a design of resonant subwavelength all-dielectric nanostructures with tailored efficiencies of nonlinear optical phenomena at the nanoscale.

The spatial filtering of optical signals has been demonstrated previously with metasurface thin-films created from arrays of structured optical elements. We consider the problem of changing the symmetry of their response with changes to the in-plane wavevector k_I→-k_I and show it can be tailored or even dynamically tuned. Our work is based on a general theory of metasurfaces constructed from non-diffracting arrays of coupled metal particles. We present the optical transfer function of such a metasurface, identify the physical properties essential for asymmetry and demonstrate its behaviour experimentally.

Efficiency of optical frequency conversion in quadratic media critically depends on spatial modulation of the nonlinear optical response of the materials. This modulation ensures, via the quasi phase matching (QPM), an efficient energy exchange between optical waves at different frequencies. The QPM structures, also known as the nonlinear photonic crystals, offer a variety of novel properties and functionalities that cannot be obtained in uniform nonlinear crystals. In particular the 3-dimensional modulation of nonlinearity allows one to realize the so-called nonlinear volume holograms which extends the concept of volume holography to nonlinear optics. Nonlinear volume hologram represents the 3- dimensional distribution of the nonlinear polarization which arises from interaction between input fundamental beam and generated wave with complex wave front, in medium exhibiting quadratic nonlinearity (χ⁽²⁾). When illuminated by fundamental beam, the nonlinear hologram gives rise to a wave at different frequency (e.g. second harmonic of fundamental wave) having complex intensity distribution following the transverse structure of the hologram itself. In this way one can combine generation of waves at new frequencies with simultaneous shaping of their transverse and longitudinal intensity profiles. In this work we present formation of various types of nonlinear volume holograms in ferroelectric crystals by using unique all-optical domain inversion technique and demonstrate their application in optical wave-shaping.

In recent years, ultracold atoms trapped in periodic lattices have attracted much attention as a simulator for condensed matter systems because of the ability to manipulate and precisely control the ultracold atoms. Periodic arrays of magnetic microtraps patterned on a magnetic film provide a potential complementary tool to conventional optical lattices for trapping arrays of ultracold atoms. Compared to optical lattices, magnetic lat- tices allow a higher degree of design flexibility by allowing almost arbitrary lattice geometries and they also allow lower technical noise and state-selective trapping of atoms. This paper reports the trapping of ultracold ⁸⁷Rb atoms in 0.7 μm-period triangular and square magnetic lattices integrated on an atom chip as a step towards using magnetic lattices as a new platform for simulating condensed matter and quantum many-body phenomena in nontrivial lattice geometries.

Bose-Einstein condensates (BECs) are ideal tools for exploring analogies to other physical systems, including condensed matter systems, because of the easily tunable parameters. In the realm of condensed matter physics, BECs can be used to provide insight into the super fluid-Mott insulator transition, topological insulators, and other quantum Hall effects.

We report progress towards realizing discrete time crystals using a BEC of potassium-39 atoms bouncing on an oscillating mirror. In the absence of interactions, each bouncing atom performs classical motion in which there are resonant islands in phase space located around periodic orbits whose periods match an integral multiple s of the driving period T of the mirror. If all the atoms are prepared in a single wave-packet, in the absence of interactions they tunnel to neighbouring wave-packets on a timescale determined by the driving amplitude and period of the oscillating mirror. In the presence of a sufficiently strong attractive interaction, the Floquet eigenstates of the periodic system become Schrödinger cat-like states, so that measurement of the position of just a single atom is sufficient to break the timetranslation symmetry and cause the system to collapse into one of the s wave-packets bouncing with period sT. Such a system allows dramatic breaking of discrete time translation symmetry where the symmetry-broken state evolves with a period typically s=40 times longer than the driving period and does not decay. This system provides also a suitable platform for demonstrating a wide range of condensed matter phenomena in the time domain.

Atom-Trap Trace-Analysis (ATTA) is a technique aimed at a measuring the relative (in comparison to the common isotope) abundance of exceedingly rare noble gas radio-isotopes (Ar-39, Kr-81 and Kr-85), for the purposes of dating water, ice and other materials that contain trapped gases. These isotopes exist with an extremely low natural abundance and require measurement capability down to parts in 1017. The noble gas dating protocol is similar to that of radio-carbon dating but, the three isotopes together, allow dating of materials in complementary ranges to that possible with the radiocarbon technique. In a facility jointly created by CSIRO, Griffith and Adelaide Universities, we use laser guidance, cooling and trapping to perform isotopic separation using the isotopic dependence of atomic energy levels. The facility is currently undergoing construction but has been shown to be able to produce metastable Ne and Ar, which can then be laser cooled and trapped. When combined with the existing gas separation facility at the CSIRO Waite facility, which efficiently extracts pure noble gases from that are dissolved in water or ice samples, we should be in a position to start measuring the age of real-world samples in the early part of 2020. In addition, to describing the current state of construction, we will also discuss two more efficient approaches for creating metastable atoms that can reduce samples size and avoid unwanted cross-contamination between samples.

The group of zincblende III-V compound semiconductors, especially (100)-grown AlGaAs and GaAs, have recently been presented as promising materials for second harmonic generation (SHG) at the nanoscale. However, major obstacles to push the technology towards practical applications are the limited control over directionality of the SH emission and especially zero forward/backward radiation. In this work we provide both theoretically and experimentally a solution to these problems by presenting the first SHG nanoantennas made from (111)-GaAs embedded in a low index material. These nanoantennas show superior forward directionality compared to their (100)-counterparts. Most importantly, it is possible to manipulate the SHG radiation pattern of the nanoantennas by changing the pump polarization without affecting the linear properties and the total nonlinear conversion efficiency.

Optical angular momentum provides a useful dimension for data multiplexing and quantum entanglement. However, the demultiplexing of optical angular momentum is often performed by complex bulk optics and multiple detectors. Here we demonstrate that chiral plasmonic electrodes can be used to selectively detect optical angular momentum in a compact and integrated format. We demonstrate direct detection of photon spin and investigate methods for the detection of orbital angular momentum.

Switching the scattering direction of high-index dielectric nanoantennas between forward and backward, via Mie resonances in the linear regime, has been widely studied, recently. However, switching the harmonic emission of nanoantennas without applying any physical change to the antennas, such as geometry, or environment, is a chal- lenging task that has not been demonstrated yet. Here, we investigate multipolar second-harmonic switch from GaAs nanoantennas. Based on the peculiar nonlinearities of zinc-blende semiconductors, we demonstrate both theoretically and experimentally unidirectional nonlinear emission routing and switching via pump polarization control. Our results offer exciting opportunities for nonlinear nanophotonics technologies, such as nanoscale light routing elements, nonlinear light sources, nonlinear imaging, multifunctional flat optical elements.

We have studied the bandwidth of atomic magnetometers based on nonlinear magneto-optical rotation (NMOR). We demonstrated broadband, high-bandwidth magnetic field measurements from DC up to 100kHz with two different techniques. The first technique measures the instantaneous phase evolution of the optical polarisation rotation in the temporal domain which enabled quantitative measurements of modulated magnetic fields up to 100kHz for a carrier frequency of 30kHz, while the second method employs active feedback techniques to track magnetic field fluctuations up to 100kHz, approximately 2800-fold greater than the passive bandwidth. For the latter case, a slew rate of 91.4nT/μs and a sensitivity of 200fT/Hz^1/2 around 8Hz have been achieved at a bias field of 50μT.

We demonstrate fabrication and characterizations of intrinsically magneto-sensitive fiber with potential applications as a high-efficiency remote magnetic field sensing platform. The fibre was fabricated using lead-silicate glass and the rod-intube fibre drawing technique. The thin glass rod of ~1 mm diameter was first coated with nitrogen-vacancy (NV) centreenriched diamond particles of ~1 μm diameter, and subsequently inserted into the glass outer tube. This rod-in-tube assembly was drawn down to fibre, with the diamond particles distributed at the fused interface between rod and tube. We experimentally coupled 532 nm continuous-wave laser into a 30-cm-length fibre piece from the fibre endface, and examined the photoluminescence (PL) properties of the fibre from both the side of the fibre and the output end of the fibre. PL mapping results showed that the glass-embedded NV emitters showed bright and photostable fluorescence, demonstrating characteristic NV centre zero phonon line emission. Moreover, the mapping result obtained at the output end of fibre indicated that the transmitted NV fluorescence was coupled into the propagation modes of the fibre. By using optically detected magnetic resonance (ODMR) from the NV ensemble along the fibre, we demonstrate detection of local magnetic fields via longitudinal excitation and side collection. Based on the current light transmission and collection configuration, the hybrid diamond-glass optical fibre sensor demonstrated a shot noise-limited DC magnetic field sensitivity of 3.7 μT/√Hz at room temperature. Our results open the possibility of robust, field-deployable fibre optical magnetometry.

In this paper, we report the response of Cobalt-60 gamma irradiation on Photonic Crystal Fibre Bragg gratings (PCFFBGs) and standard commercial FBGs (STD-FBGs). Optical measurements were performed to determine the shift of the Bragg wavelength as a function of accumulated dose and relaxation time. To simulate real time conditions of a radiation dosimeter, the FBGs are examined through three consecutive radiation stages followed by very limited recovery times. We were able to obtain a Bragg wavelength shift with both sets of FBGs. The PCF-FBGs response included strong recovery after each irradiation compared to the STD-FBGs. This makes the PCF-FBGs strong candidates as optical fibre FBG sensors in the area of radiation dosimetry.

In this paper we demonstrate high strength (Κ< 4 cm^-1) grating imprinting using excimer KrF UV laser for underwater DFB fiber laser sensing applications. The FPGA-controlled stepping recording system allows for the recording of long (up to 52mm) gratings with error compensation, chirping and apodisation for side-lobe suppression and at arbitrarily high exposures. Batch recording of fibre gratings (4 fibres/mm) was also proposed and demonstrated.

Certain spider silks, as used in aerial orb webs, are high quality optical micro-fibers with widths of 1 to a few microns and a refractive index of ~1.55. It has been reported that such silks have reduced relative reflectance in the ultra-violet and violet, as compared to the rest of the visible light spectrum with implications for their visibility to insect vision. Relative reflectance as a function of wavelength gives no insight into the fraction of the intensity of light that falls on a spider silk that will be backscattered/reflected into a solid angle such that it might result in it being visible to an oncoming insect, for example. We will report comparative results from measurements of the radial silks of four orb web weaving spider species. These species evolved at different times and/or to exploit different biological habits. One species is nocturnal. Combining the results of photoreflectance measurements and optical surface profiling studies shows how the geometry of the spider silks may have evolved to reduce the scattered/reflected light from the radial silk of certain species. The properties of certain spider silks as an optical material with low UV absorption also emerge from this study.

Fluorescence images approaching sub-micron resolution are formed in thin nanocrystalline phosphor films. The images are created with UV exposure of the films under chrome-coated quartz masks. The UV light locally changes the valence state of the samarium ions in the nanocrystalline phosphors to activate fluorescence properties. The red fluorescence images are then read-out with blue-violet light. With an imaging resolution approaching the diffraction limit, this technology has potential for anti-counterfeiting labelling or optical data storage applications.

We report on the latest development of our photonics-based brain-machine interface. This work done in collaboration between UNSW and Macquarie University – and supported by the US Office of Naval Research – directly addresses the long-term DARPA challenge of producing implantable chips with 1 million neural connections. To the best of our knowledge, no technology has demonstrated the potential so far to scale up to such a massive number of channels.

Optical sensors based on chalcogenide glass fibers transparent in the mid infrared (MIR) spectral range from 2 to 16 μm (4000 to 625 cm^-1) have been developed in order to analyse biological and chemical samples. These sensors are based on the Fiber Evanescent Wave Spectroscopy (FEWS) principle. Indeed, most of the molecules have their functional groups absorption bands in the mid infrared region and the fibers are able to detect the characteristic vibrations these of molecules. First, fibers have been developed in the frame of large-scale projects such the DARWIN mission in order to permit the detection of CO₂ at 15 μm. A large activity was focused on the synthesis of Te-Ge-Se glasses, containing no more than 3% of Se but stable enough to draw fibers transmitting light until 16 μm. Then, single mode fibers have been successfully fabricated thanks to a new preform molding process. Finally, the growing need for sensors able to detect diseases in the medical domain or polluting molecules in the environmental area led us to develop very stable Te-Ge-AgI low loss fibers. These fibers have been implemented in FEWS experiments permitting detection of biomolecules, like sugars and lipids and emerging pollutants like benzene, and chloroform, in the spectral domain extending from 2 to 16 μm. To our knowledge, it is the first time that spectra are collected on such a wide range of wavelengths.

This paper reports on a multi-point optical fiber pressure sensor using fiber Bragg gratings (FBGs) written on an exposed core optical fiber (ECF) by femtosecond laser. The pressure sensing elements were constructed as Fabry-Perot (FP) interferometers of different cavity lengths using pairs of FBGs with identical resonant wavelength. In this fashion an interference pattern was formed within the FBG bandwidth with much narrower fringes, leading to better detection limit. Fast Fourier transform (FFT) was used to calculate the phase change of the FP interference pattern with respect to applied pressure. The pressure sensitivity was proportional to the cavity FP cavity length, and reached -0.672 rad/MPa for the case of FP with 9 mm cavity length. The proposed sensor has potential to measure pressure at very high temperature thanks to its single material configuration.

Nanoscale thermometry of biological systems offers new insights into cell metabolism at a sub-cellular scale. Currently, there is no way in which we can achieve high resolution temperature sensing on these systems without the use of foreign materials such as biological markers. Using rare-earth doped tellurite glass as a platform for thermometry, we report micron scale scale temperature sensing via confocal scanning microscopy. We demonstrate this technique by monitoring the cooling from a water droplet and report a net temperature change of 7.04K with a sensitivity of 0.12K. These results pave the way for “marker free” micron scale temperature sensing in biological systems.

Latest advances in integrated single-photon detectors offer possibilities for gaining information inside quantum photonic circuits. We introduce a concept and provide experimental evidence for the inline tomographic mea- surement of multiphoton quantum states, while keeping the transmitted ones undisturbed. We establish that by recording photon correlations from optimally positioned detectors on top of coupled waveguides with de- tuned propagation constants, one can perform robust reconstruction of multiphoton density matrices describing the amplitude, phase, coherence and quantum entanglement. We report proof-of-principle experiments. Our method opens a pathway towards practical and fast inline state tomography for diverse applications in quantum photonics.

Lithium niobate is widely used in photonics applications because of its large second order nonlinearity and the possibility of integrating nonlinear parametric processes and fast electro-optical reconfigurability. Here we show how these properties can be used for continuous variable quantum optics experiments including the generation, manipulation and characterization and detection of squeezed light.

Accessing complete information about the emission from any quantum-optical systems requires tools capable of a frequency-resolved characterization of multi-photon transitions that would go beyond the standard _g⁽²⁾ correlation measurements. This is particularly important when analyzing systems which exhibit strong nonlinear response with multiple emission pathways. In this work, we calculate and analyze in details correlations of light emitted from two such canonical nonlinear optical systems, one incorporating Kerr nonlinear medium, and another exhibiting optomechanical coupling between light and quantized motion of a generic mechanical oscillator. We compare their single- and two-photon emission characteristics by employing a recently developed framework that allows us to calculate the frequency-resolved _g⁽²⁾ correlations between emitted photons with two arbitrary frequencies. Our analysis shows a rich landscape of bunching and antibunching associated with multi-photon emission events, and reveals the distinctive temporal characteristics of such processes. This new understanding provides a new asset to characterize and exploit nonlinear phenomena in Kerr and optomechanical systems in future experiments.

A holmium non-linear polarisation rotation (NLPR) all-fibre mode-locked laser was characterised. The radiofrequency (RF) spectrum of the pulsed train output was used as an automation metric. Non-ideal pulsing behaviour was corrected by changing the intracavity polarisation state using actuators in an electronic polarisation controller. The optimum cavity produced mode-locked pulses with a central wavelength of 2.061 μm and an 8.7 nm optical full-width-at-half-maximum (FWHM).

The yellow spectral region has applications in medicine, ophthalmology, acne treatment, and ytterbium based optical clock, which is recommended as the secondary representation of System International (SI) second. Lasing in this spectral region can be achieved by using sum frequency and second harmonic generation, which are complex methods. Here, we have reported the first (to the best of our knowledge) GaN laser diode pumped dysprosium (Dy) doped ZBLAN fibre laser for yellow lasing using a simple setup. Due to the four-level system, the laser oscillation threshold is low and about 7.0 mW for 0.6 m of Dy-doped ZBLAN fibre. However, the maximum slope efficiency is only 2.3% with the available 2% output coupler. In our investigation, we have identified two possible factors, fibre background loss and pump excited state absorption, for such a low slope efficiency.

Gravitational wave detectors rely on the interference of light at the asymmetric port of a Michelson interferometer. The required light sources for these detectors are high power (200 W) with low intensity and frequency noise [1]. These requirements are currently met with the amplification of a monolithic single-frequency Nd:YAG non-planar-ringoscillator (NPRO) [2]. To improve the sensitivity of next generation detectors, cryogenic silicon test masses have been proposed to reduce the thermal coating noise. Laser sources near 2000 nm appear promising as they lie in the silicon transmission window and have reduced absorption in the amorphous silica coatings which reduces the heat-load on the cryogenically cooled mirrors [3]. High power thulium-doped fibre amplifiers provide broad emission in this wavelength range and have previously been demonstrated with high power and narrow linewidths [4]. Suitable thulium NPRO sources are not commercially available and an alternative seed source is required to determine the noise characteristics of these amplifiers.

We describe the lasing behaviour of an all-fibre laser with saturable absorber with emphasis on observed hysteresis and bi-stable dynamics for certain parameter regimes. The fibre laser is a simple Fabry Perot cavity with Erbium and thulium doped sections that provide optical gain and saturable absorption respectively. We explore methodically laser behaviour for consecutive up and down scans of optical pump powers for up to 13 unique experimental configurations using different lengths of the absorber section (ranging from 0.21 m to 1.48 m). We report interesting bistable behaviour as well as hysteresis which exists for a narrow range of saturable absorber lengths(0.66 m to 0.78 m).

Quantum mechanics is a robust theory which pro duces highly accurate predictions. Despite its successes, it is still plagued with controversies like the measure- ment problem. In short, the measurement problem is the conflict between the evolution of the wavefunction described by Schro¨dinger’s equation and the apparent collapse of the wavefunction after a measurement is done. The Wigner’s friend paradox illustrates the conflict be- tween the two rules. In the thought experiment, we consider an observer (Wigner’s friend) who is able to per- form measurement on the quantum system and assign a quantum state. Wigner is a super-observer who is able to measure the laboratory his friend is in and also as- sign a quantum state. This process, however, leads to a quantum state that does not ascribe a well-defined value to the outcome of the friend’s observation, in apparent contradiction with the friend’s perspective.

In this work we couple bright room-temperature single-photon emission from a hexagonal boron nitride atomic defect into a laser-written photonic chip. We perform single photon state manipulation with evanescently coupled waveguides acting as a multiple beam splitter, and generate a superposition state maintaining single photon purity. We demonstrate that such states can be utilized for quantum random number generation.

Quantum communication requires long-lived memories and robust communication qubits. Long-lived memories and high fidelity two qubit gates are demonstrated using atomic qubits. Frequency qubits are shown to be robust against noises present in long distance communications. In this project we are working towards using trapped ¹⁷¹Yb+ ions as memory qubits and frequency encoded photonic qubits as communication qubits to realise long distance quantum communication protocols.

Frequency combs, analogue to digital sampling, and free space optical communications are emerging applications that can benefit from advances in elegant, compact, and high-performance miniature mode-locked lasers. By virtue of their ‘chip-scale’, and multiplicity of adjacent waveguides, compact planar waveguide devices are suited to efficiently operate in the ~0.5 GHz to 10 GHz pulse regimes, and to have key advantages when employed as dual-frequency combs. The erbium ytterbium cerium co-doped ZBLAN chips we have developed have achieved transform limited mode-locked output near 1.55 μm, pulse lengths down to 180 fs, and operation up to 5 GHz. This paper will also cover our more recent work on demonstrating a dual-frequency comb based on simultaneously mode-locking adjacent waveguide lasers in a common-cavity setup and demonstrate its spectroscopic potential by rapidly (~ms) acquiring high resolution and broad (<2 THz) molecular spectra of molecules.

High-power single-longitudinal-mode (SLM) lasers are crucial for applications such as LIGO, sodium guide stars, isotope separation and atom cooling, but are challenging due to gain profile inhomogeneities and spatial hole burning. This work shows that a SLM 620 nm laser is firstly achieved using a standing-wave diamond Raman resonator with intracavity second harmonic generation (SHG). In addition to the benefits of the spatial hole burning-free gain medium [1], SHG provides a valuable additional mechanism for increasing gain competition and therefore enhancing SLM stability. Nascent secondary modes experience double the nonlinear loss in the SHG crystal due to the role of sum frequency generation with the primary mode [2]. A further feature of the current external standing-wave cavity design is that the cavity is non-resonant at the pump frequency, thereby allowing the laser to be pumped without mutual control of the wavelength and cavity length and by using multi-longitudinal-mode (MLM) lasers with a spacing different to the free-spectral-range of the diamond Raman laser.

We report on the latest results towards a compact ultra-high repetition rate Yb-doped fluorozirconate laser, based on a simple and robust extended cavity design. Preliminary results show a laser operates with a pulse width of 2.5 ps and a repetition rate of 276 MHz at λ = 1018 nm. By controlling the dispersion and intracavity loss it should be possible to decrease the pulse width and increase the repetition rate to multi-GHz range.

Through their small modal volumes and ultra-high finesse, optical microresonators are capable of exhibiting rich nonlinear behaviour, driven by pump powers in the milliwatt range. Microresonators with Kerr type non- linearities have been the focus of much research, resulting in the demonstration of chip-scale coherent optical frequency combs, underpinned by four-wave-mixing. Here, we consider a four-wave-mixing process in microresonators which generates widely-separated parametric sidebands, symmetrically spaced around the pump.

Supercontinua generated in microstructured optical fibre are now used widely. The detailed spectral and temporal behaviour arising from the processes causing the extreme spectral broadening remains of interest particularly where users require temporal stability for specific visible wavelengths generated by a supercontinuum source. The theoretical gravity-like potential model requires NIR Raman self-frequency shifted solitons in the anomalous dispersion region of the fibre to be phase matched with short wavelength dispersive waves travelling in the normal dispersion region of the fibre. This is difficult to probe in the fundamental EM mode of the host fibre as competing wavelength generating and spreading non-linear processes obscure results. Here, specific high order EM modes excited in the fibre generate a spectrally sparse supercontinuum which was investigated using polarization and spatio-spectral mapping to provide unequivocal phase matching evidence supporting the gravity-like trapping model. Further, polarization measurements reveal that the input polarization state is scrambled due to non-linear effects within the fibre during supercontinuum generation, having implications for interferometry using supercontinua.

We report a fibre laser incorporating an intracavity pulse-shaper that induces a large anomalous net cavity quartic dispersion in which the mode-locked pulses propagate as pure-quartic solitons. We characterize the laser output pulses using a set of spectral and temporal phase resolved measurements and resonant dispersive wave analysis, and find that the results are in excellent agreement with analytic predictions.

We experimentally demonstrate enhanced optical Kerr nonlinearity of hybrid integrated waveguides coated with layered graphene oxide (GO) films. Owing to the high Kerr nonlinearity of GO and strong mode overlap between GO and waveguide, up to ~9.5-dB enhancement of four wave mixing (FWM) conversion efficiency is achieved.

Self driving cars offer the potential to be a safer, more economical and more environmentally friendly transport option. High performance LiDARs are one of the primary enabling sensing technologies vital to autonomous vehicles to meet the demanding requirements for full autonomy. We discuss the role of automotive LiDAR in autonomous vehicles, and the performance requirements and optical technologies that high performing LiDARs need to achieve to fulfill that role.

Optical phased arrays (OPAs) are a solid-state device able to manipulate the distribution of optical power without the use of mechanical beam steering systems and have potential applications in free-space laser communications, target acquisition and tracking, and interferometry. Here we present a scalable OPA and digital control architecture capable of steering a laser beam at MHz frequencies, and having arbitrary control over the beam wavefront.

High performance beam steering techniques are essential for 3d imaging systems, and in particular automotive LIDAR. We present a high-speed, chip-scale, dynamically reconfigurable beam steering system suitable for use at telecom wavelengths. Our technique relies on sub-microsecond electro-optic switching between discrete outputs in a waveguide network. This beam steering technology, along with a coherent detection technique is used to demonstrate simultaneous ranging and Doppler velocimetry of targets with an amplitude modulated continuous wave solid state LIDAR system in a laboratory environment.

We present a continuous wave Light Detection And Ranging (LiDAR) sensor that instantaneously measures distance and radial velocity with strong immunity to interference (e.g., other LiDAR sensors, glare). By automatically prioritising measured information based on velocity and range, our aim is to reduce the processing time required to execute safety-critical decisions in autonomous applications.

Wave propagation is a linear process in the time domain in the absence of loss. This property has been exploited over the past 20 years for wave control through highly disordered media. Let’s consider a short pulse propagating through a disordered system. If the field associated to the pulse is recorded and played backwards, the wave is focused back to the source at a single delay. This time reversal control has been evidenced for low frequency waves such as acoustics, water waves and microwaves. Over the last decade, partial spatiotemporal control of optical waves has been demonstrated by means of spatial light modulators. However full optical time reversal remains elusive. In this paper, we demonstrate time reversal of optical waves with a device that can manipulate independently amplitude and phase of 90 spatial and polarization modes, over 4 THz of bandwidth and 20 ps of delay. For the first time we demonstrate arbitrary control of all the degrees of freedom: spatial (amplitude and phase), polarization, spectral and temporal after propagation through a multimode fiber. This new ability to control and manipulate at will optical waves opens promising opportunities for linear and nonlinear optical phenomena, such as imaging and optical communications.

In this contribution, we demonstrate the deposition of low loss, CMOS-compatible SiN thin-films using plasma beam assisted reactive sputtering for photonic integrated circuits. Plasma beam assistance during the deposition process enabled us to achieve thin-film losses of below 0.1 dB/cm and a surface roughness of R_q of <0.1 nm, while keeping the processing temperatures below 400°C. Propagation losses of 0.9 dB/cm at 1550 nm have been achieved for waveguides with a cross section of 460× 2000 nm (height × width).

The detection of quantum errors is of particular importance to the development of reliable engineered quantum systems. Whereas previous error-detection schemes were mostly developed for π phase-flip associated with solid-state qubits, here we introduce a protocol for direct detection of arbitrary continuous phase errors in the transmission of multiphoton spatially entangled quantum states. We present a design and experimental evidence for its realization in an integrated photonic circuit using gradually coupled waveguides with specially detuned propagation constants. We anticipate that our approach will facilitate the development of error-robust photonic devices for the processing and communication of quantum information.

Advanced photonic filters implemented by cascaded Sagnac loop reflectors (CSLRs) in silicon-on-insulator (SOI) nanowires are experimentally demonstrated. Based on mode splitting in these standing-wave (SW) resonators, we achieved diverse filtering shapes for spectral engineering showing good agreement with theory.

A CMOS compatible three-dimensional (3D) integrated photonics circuit for multilayer silicon photonics is reported. Slopes with angles between 10o and 15° were created in the oxide layer using single step wet etching to connect the two Si waveguide layers. Amorphous Si (a-Si) deposited using hot wire chemical vapor deposition (HWCVD) at a temperature of 230°C was used to fabricate the device. Losses of 0.5 dB/slope were measured in the slope waveguides at 1310 nm wavelength. As a demonstration, we propose a 4x4 network switch using a-Si based vertical directional coupler.

The rapid measurement of gas concentrations is beneficial to a broad range of applications, including pollution monitoring, high-precision spectroscopy, and medical breath analysis. Optical frequency combs (OFCs) are a near-ideal optical interrogation source for molecular spectroscopy, combining broadband light with high frequency-precision and dense spectral sampling, characteristics which also allow short measurement times. A spectrometer based on a virtually imaged phased array (VIPA) is used to unravel the comb into a high-resolution transmission spectrum, with the returned spectra rapidly fitted with a detailed spectral model for concentration extraction of CO₂. We demonstrate an accuracy of 0.5% and 12% for concentration measurements of ¹²C¹⁶O₂ and ¹³C¹⁶O₂ respectively, with the measured isotopic ratio in excellent agreement with that expected from their natural abundances. Precision of the concentration measurements is also high, at 0.03% and 1.24% for ¹²C¹⁶O₂ and ¹³C¹⁶O₂ respectively. The measurement technique is also verified to be highly linear for concentrations ranging over three orders of magnitude. The spatial and temporal coherence of OFCs additionally enables the use of the full range of performance-enhancing optical techniques including resonant enhancement. Here we demonstrate the use of a multi-pass Herriott cell to enhance the effective measurement path length, which allows the continuous optical measurement of CO₂ production during the respiration of baker’s yeast in a closed system. Results from the yeast experiments agree well with existing literature.

Quantum optical information systems offer the potential for secure communication and fast quantum computation. To fully characterise a quantum optical system one has to use quantum tomography.1 The integration of quantum optics onto photonic chips provides advantages such as miniaturisation and stability, significantly improving quantum tomography using both re-configurable, and more recently, simpler static designs. These on-chip designs have, so far, only used probabilistic single photon sources. Here we are working towards quantum tomography using a true deterministic source - an InGaAs quantum dot.

The concept of using multiple-pass technique to improve the axial resolution of a reflection mode confocal system is presented. The propose technique allows further diversion on the given out-of-focus rays from entering the pinhole, imposing a more stringent limit for rays around the in-focus region to be detected as confocal signal. The feasibility of the propose technique was experimentally examined. The comparison of the full width at half maximum (FWHM) of the normalized intensity profiles shows that the axial scanning resolution achieved by the proposed technique is twofold of that of the conventional technique.

Advances in sensing and signal processing based on microwave photonics are presented with a focus on high resolution sensing via microwave photonics, integrated microwave photonic filtering and phase shifters for beamforming.

We present two new designs of optoacoustic waveguides supporting nonlinear Brillouin scattering (SBS). The first design, optimized for forward SBS, comprises a rectangular core supporting a low-loss optical mode, suspended in air by a series of transverse ribs. The ribs are engineered to exhibit a complete acoustic stopband and suppress the transverse leakage of acoustic waves. The second design we discuss here is a realization of an Anti-Resonant Reflecting Acoustic Waveguide, which are analogues of optical ARROWs. These waveguides, capable of co-localization and guiding of both the optical and GHz acoustic waves in simple, translationally invariant waveguides, are shown to support backwards SBS.

We experimentally demonstrate integrated waveguide polarizers and polarization-selective micro-ring resonators (MRRs) incorporated with layered graphene oxide (GO) films. We achieve a high polarization dependent loss (PDL) of ~53.8 dB for the GO-coated waveguide and a high polarization extinction ratio of ~8.3 dB for the GO-coated MRR.

We have investigated the effect of the frequency shift associated with an acousto-optic (AO) interaction on the spectral quality of acousto-optically tuned external cavity semiconductor lasers. A ring-cavity was built and the wavelength controlled by a frequency compensating acousto-optic tunable filter pair, which allowed user control over the frequency shift of the interacting light. Laser spectra were recorded for a range of frequency shifts, and a 30 kHz driving frequency gave the optimal spectral response where the output spectral shape did not vary as a function of operating wavelength and resulted in <0.1 nm linewidths.

The development of the first Yb³⁺ doped microchip and waveguide laser in germanate glass (GPGN) is reported with a composition of 54GeO₂-31PbO-4Ga₂O₃-9Na₂CO₃-1.5Yb₂O₃ (Yb³⁺: GPGN). Up to 51mW at 650mW of input power is obtained from a L=4.5mm long cavity microchip laser operating at 1052nm with slope efficiency of ~30% and laser threshold of ~230mW. Single track (type 1) waveguides are inscribed 150μm beneath the surface of the sample in the femtosecond laser cumulative heating regime. Pulse energies range from15nJ to 75nJ producing guiding structures ranging from d= 12μm to 60μm. Waveguide laser operation is achieved for a 24μm diameter waveguide with up to ~20mW output power generated at 1.07μm for 650mW of 976 nm pump power.

We present a compact design for a 1064 nm Q-Switched waveguide laser based on a liquid crystal transducer. Directly integrating the input-coupling mirror on the chip and utilising a Grin lens to also integrate the modulator optics enables a miniaturised setup. The preliminary experimental results have demonstrated that the Q-switched laser pulses with a pulse width of 45 ns and average output power of 4.5 mW can be achieved with a pump power of 350 mW, when an electrical signal with a repetition rate of 5 kHz, a peak-to-peak voltage of 30 V and a duration of 4 µs is applied. This work was supported by the Office of Naval Research Global (N62909-18-1-2147).

Coherent excitation and stimulated emission from optical transitions has been proposed as a mechanism to generate strong coherent forces in atomic systems and as the basis for fast quantum gates in trapped ions. We have demonstrated driving coherent oscillations between the ²S_1/2 and ²P_1/2 states in trapped ¹⁷¹Yb⁺ with 2.5 ps pulses straddling the resonance at 369.5nm. At higher powers nearly full extinction was observed, demonstrating coherence, however residual detuning issues have precluded full coherent population transfer.

We demonstrate the first stable mode-locking from an Er³⁺ doped fluoride fibre laser cavity using various novel two-dimensional saturable absorber materials such as PtSe₂ and MXene operating near 2.8 μm wavelength to the best of our knowledge. The linear cavity includes a high reflective chirped fibre Bragg grating to provide wavelength stability. The observed mode-locked pulse train has a 30 MHz repetition rate and an average power of 223 mW. Our results demonstrate the feasibility of using the novel two-dimensional nanomaterials such as PtSe₂ and MXene into the fibre laser cavity for the application in mid-infrared wavelength regime.

The next-generation gravitational wave detectors aim to enhance our understanding of extreme phenomena in the Universe. The high-frequency sensitivity of these detectors will be maximized by injecting squeezed vacuum states into the detector. However, the performance advantages offered by squeezed state injection can be easily degraded by losses in the system. A significant source of loss is the mode mismatch between optical cavities within the interferometer. To overcome this issue, new actuators are required that can produce a highly spherical wavefront change, with minimal higher order aberrations, whist adding low phase noise to the incident beam.

We report mid-infrared supercontinuum generation in a silicon germanium-on-silicon waveguide. We show that, by adding a chalcogenide cladding, it is possible to trim a posteriori the waveguide’s dispersion profile which, in turn, governs the properties of the generated supercontinuum. In particular, we experimentally show that a shift from anomalous to normal dispersion takes place when a 1.26 μm thick cladding layer of Ge_11.5As₂₄Se_64.5 is added. Finally, we show that the group velocity dispersion of the waveguide can be precisely controlled by changing the thickness of the cladding layer.

Compared to oxide based glasses, vitreous materials composed of chalcogen elements (S, Se, Te) show large transparency windows in the infrared. Indeed, chalcogenide fibers can be transparent from the visible up to 12-15 μm, depending on their compositions. The IR signatures of most molecules, including biomolecules, are located in this spectral domain, which allows in situ, non-invasive and real-time detection of gaz or organics molecules. Indeed, chalcogenide glasses can present a high non-linear coefficient (n2), 100 to 1000 times larger than for silica glass, depending on the composition. An original way to obtain fibers is to design microstructured optical fibers (MOFs). These fibers present unique optical properties thanks to the high degree of freedom in the design of their geometrical structure. Various chalcogenide MOFs operating in the mid-IR range have been elaborated in order to associate the high nonlinear properties of these glasses and the original MOF properties. Different glass compositions and different designs have been achieved depending on the intended application. Indeed, chalcogenide MOFs might lead to new devices with unique optical properties in the Mid-IR domain like multimode or endlessly single mode transmission of light, small or large mode area fibers, non-linear properties for wavelength conversion or generation of supercontinuum sources. In this work, a supercontinuum from 2 to 10 μm, with an average power of 15mW, has been obtained in a chalcogenide MOF by pumping with a supercontinuum generated in a fluoride fiber.

We report the characterization of arrays of micropillars fabricated in an n-type 4H-SiC using photolithography to enhance the emission of bandgap color centers in silicon carbide emitting in the spectral region from 850 nm to 1400 nm. The emission is identified by the mono-vacancy of Si (V_Si), silicon and carbon divacancy (V_CV_Si), and the nitrogenvacancy (NCV_Si) using low-temperature micro-photoluminescence. These emitters are created in large ensemble by using ions implantation and annealing at a different temperature to extend the emission in the O-band region. The optical fluorescence enhancement experimental results are obtained using custom made IR confocal microscope to measure integrated PL of up to a factor of 20 compared to bulk material. This enhancement is supported by finite-element simulations considering the non-unity quantum efficiency of the emitters and their broad spectral emission at room temperature. Our study provides the pathway for quantum sensing device design and fabrication with an integrated ultrabright emission for in vivo imaging in the infrared.

The advancing precision of modern atomic spectroscopy is beginning to afford optical tests of fundamental physics in helium through, for instance, nuclear charge radii determinations. Helium therefore provides a testbed as appealing as Hydrogen for spectroscopic tests of QED. Among outstanding discrepancies between predicted and observed Helium transition lines are the 7.5σ difference in the n = 3 singlet-triplet splitting and the 93σ difference between Martin’s measurements of the 2³P₂ → 5³S₁ and 2³P₂ → 5³D transitions values, and recent predictions by Drake [3]. We contribute to both of these by measuring five transitions from the 23P2 state, improving on Martin’s measurements with an order of magnitude greater precision, and making the first observation of the spin-forbidden 2³P₂ → 5¹D₂ transition in Helium. Our measurements constrain the 5³D and 5¹D ionization energies of 4He[4] to 150 parts per billion, and the 5³S to 28 parts per billion.

We propose and demonstrate a reconfigurable microwave signal processor for fractional and regular Hilbert transform with 17 GHz bandwidth based on an integrated Kerr optical frequency comb source. Transmission responses and temporal characterization are experimentally demonstrated.

We demonstrate an orthogonally polarized optical single sideband (OP-OSSB) generator based on dual cascaded micro-ring resonators (MRRs). We achieve a large tuning range of the optical carrier to sideband ratio of up to 57.3 dB. The operation RF frequency of the OP-OSSB generator can also be continuously tuned with a 21.4 GHz range via independent thermal control of the two MRRs.

We demonstrate broadband radio frequency (RF) channelization based on a CMOS-compatible integrated optical micro-comb source, which provides a large number of wavelength channels as well as an RF operation bandwidth of ~90 GHz. We experimentally verify the RF channelization performance from ~1.7 GHz to ~19 GHz with a high spectral slice resolution of ~1.04 GHz.

A broadband microwave mixer is demonstrated based on an integrated optical micro-comb source, with an operation bandwidth up to over 60 GHz, a conversion efficiency of −6.8 dB and a spurious suppression ratio of over 43.5 dB, and experimentally verify the RF performance up to 40 GHz. This approach to realizing microwave mixers offers reduced complexity, size, and potential cost for a wide range of applications to microwave systems.

In this paper a theoretical study of highly selective plasmonic color filters is demonstrated. The filter design consist of a perforated aluminium film, where nanoholes are arranged in a square lattice. A hybrid substrate is implemented as a dielectric layer which allows high selectivity and minimum spectral cross talk. The impact of the hole periodicity, thicknesses of Si₃N₄ and metallic layer on the device performance is highlighted. The optical resonance transmission properties of the simulated plasmonic color filter including resonance position, transmission efficiency, figure of merit, and spectral bandwidth of resonance peak are also analyzed thoroughly.

State-of-the-art optical fiber communication system reaches to transmission capacity from tens to hundreds of Tb/s. The massive capacity crunch has sparked concerns regarding available bandwidth and constantly increasing optical data traffic. Certainly, one way is to broaden the spectral transmission range beyond the narrow gain band of current erbium doped fiber amplifier (EDFA). Either side of Erbium across low-loss transmission window (1.5μm) shown promising results with optical fibres codoped with rare-earth-doped materials such as bismuth/thulium. Hence, it is of crucial importance to develop broadband optical amplifier to fully utilize the uncovered spectral regions with proper choice of pump wavelength(s)/Laser diodes. Here we have compared the performances of Bismuth/Erbium and Ytterbium/Erbium co-doped fibres as pumped to 808nm to one as pumped at 830nm. The pumping excitation conditions and spectral characteristics in BEDF and EYDF are explored to maximize the lasing efficiency. Using equivalent conditions and same section of Bi/Er codoped fiber, an enhanced broadband emission with FWHM ~ 149 nm is observed in Bi active centers (BAC) related to Si around ~1420nm under 808nm excitation as compared to 830nm with its FWHM ~ 125nm at an input power of ~ 55.5 mW. At maximum power, under 808nm pumping, a well-known peak emission of Er³⁺ at 1536nm noticeably increased due to reabsorption of BAC-Si (~1420nn) with the ratio ~ 1.7 between Er³⁺ and BAC-Si emission peaks. On the contrary, emission peak of the BAC-Si revealed higher with the ratio of ~ 1.5 than that of Er³⁺ by 830nm pumping. Afterward, we observed Yb³⁺ emission at 1040nm and 980 nm using Yb/Er codoped fiber with both pumps at same power. Using 808nm pumping, an extended emission band around ~ 1230 nm appeared namely BAC-Al while the other emission bands associated with BAC-Si (~ 1480nm) and Er³⁺ (~1536nm) shown similar emission bands with high emission peaks compared to 830nm pump at equivalent pump powers. Furthermore, the emission peak of the BAC-Si is about the same level as that of Er³⁺ with ratio of RBi/Er~ 1.1 under 808nm pumping while 830 nm pump showed the ~ 5.25 ratio between the emission peaks of BAC-Si and Er³⁺. We believe that this side-by-side comparison of two pumps and two home-made fabricated codoped fibres could be useful as a promising strategy for the next-generation WDM passive optical networks employing single broadband amplifier and tunable fiber laser covering 1000-1800nm telecommunication bands.

Distributed pressure measurements from the lifting surfaces of aeronautical platforms provide valuable information to validate model predictions. These measurements are typically made on scale models of the structure in wind or water tunnels and require the sensors to be integrated into the model with minimal intrusion on the surface profile so as not to disrupt the flow. The small footprint and capacity for multiplexing of optical fibre-based sensors offer potential for successful application in this area. This paper reports on an experimental assessment of three distributed fibre optic pressure sensor designs intended for integration with the lifting surfaces of composite marine propeller blades.

We study the properties of second order solitons with two nonlinear Fourier transform eigenvalues that are very close to each other. We have found that these solitons can be approximated with a linear combination of two fundamental solitons. The error in the approximation reduces as the gap between the eigenvalues reduces. This relation can be used to explain the correlation existing between eigenvalues, nonlinear spectral amplitudes and spectral phases and to encode information more efficiently on more packed second order soliton signals.

High levels of mode matching are required for optimal performance in interferometric gravitational wave detectors that use squeezed light injection. We propose a technique for measuring the magnitude and direction of mode mismatch by inducing a radio frequency waist size and position modulation and demodulating the reflected field using a single element photodiode.

To overcome the crosstalk happening between two degenerately fundamental modes of a fiber in Terahertz (THz) regime, a novel photonic crystal fiber (PCF) that yields a wide range of single-polarization-single-mode (SPSM) propagation with large loss differences (LDs) is designed. The method used to realize this SPSM PCF is to deposit an epsilon-near-zero (ENZ) material in four selected air holes in the cladding, which ends up with four ENZ rings. These ENZ rings introduce significant LDs between the wanted (X-polarized) and unwanted (Y-polarized and high order) modes. Extensive simulation results demonstrate that the LDs between the wanted and unwanted modes vary with the thickness of ENZ rings. With a very short length (4 cm) of the proposed PCF, pure SPSM propagation, i.e., the unwanted modes are 20 dB lower than the wanted mode, can be achieved from 1 to 1.2 THz.

The device characteristics of GaSb-based mid-infrared (MIR) photonic-crystal (PC) surface-emitting lasers (SELs) were investigated with respect to depths of etched PC holes. Measurement of below-threshold emission spectra identifies the bandgap as well as band-edge modes. The bandgap separation, which is a function of feedback coupling, increases with increasing depth. From within, the Bragg frequencies and their detuning from lasing frequencies can be determined. Moreover, with increasing depth, the threshold pumping density decreases exponentially to a saturation level, which is assigned to minimum device modal gain of certain value. The relative threshold gain is then plotted as a function of normalized frequency detuning. The gain-detuning relationship of PCSELs is similar to that of one-dimensional (1D) distributed feedback (DFB) lasers.

A novel polyvinylidene fluoride (PVDF) coated fiber-optic Fabry–Perot interferometric (FFPI) sensor for temperature measurement is proposed and experimentally validated. The sensor head consists of a PVDF thin film formed by the phase inversion process via immersion precipitation at the freshly cleaved endface of a single mode telecommunications optical fibre. The resin polyvinyl butryl (butvar) was used as a cross-linker to promote good adhesion between the optical fibre glass and PVDF in order to reduce operational coupling loss. Sensor operation is demonstrated by shifts of the FFPI reflection spectra and its performance was analysed through measurement of optical thickness or path difference with temperature variation. Experimental data shows that the thermal expansion effect of the PVDF coating is more dominant than its thermo-optic effect. The proposed sensor exhibits an exponential response over 21 to 160 °C inside a tube furnace with a sensitivity that spans between 1.6 nm/°C and 7.5 nm/°C.

In this paper, we study the Nonlinear Fourier Transform of a signal formed by adding two time-separated pulses. By using the layer peeling property, we show that the eigenvalues of the signal are well approximated by the union of those for the two component pulses separately. The accuracy level of the approximation increases as the component pulses are further separated in time. Scattering coefficients and spectral amplitudes of the signal are also derived, which explain the correlation in eigenvalues, scattering coefficients and spectral amplitudes between the signal and the component pulses.

In this study, two fiber Bragg grating sensors are multiplexed using time division multiplexing. The fiber Bragg gratings are setup in a dual bus configuration and the sensor signals are detected using a transmit-reflect detection system. The results demonstrate that both the transmitted and reflected signals from both fiber Bragg gratings can be resolved when the sensors are separated by a sufficient distance.

Motivated by available methods in quantum mechanics, we have developed a novel method to find the nonlinear Fourier transform (NFT) of optical signals. Using this approach, we are able to analytically solve the matrix eigenfunction-eigenvalue equation that describes NFT and reduce it to an ordinary first order scalar differential equation. This simplifies the processes of finding the NFT of any optical signal and can potentially lead to more efficient and accurate numerical methods to find NFT.

Frequency up- and down-conversion in warm alkali vapours over a range of applied cw laser intensities has received much attention in recent years due to promising applications in the fields of remote detection, quantum information and computing, specifically in the implementation of correlated photon pairs, photon storage and quantum memory interface to name a few. The generation of directional laser-like blue and infrared light in alkali vapours has been extensively studied. However, important details of the interplay of parametric and nonparametric nonlinear processes, such as the four-wave mixing (FWM) and amplified spontaneous emission (ASE) responsible for the new field generation, are not entirely clear.

Conducting polymers are widely researched in terms of both their electrical and optical properties. The optical properties are typically observed on the macroscopic scale. To broaden their application, fabrication and char- acterization of conducting polymers on the nanoscale thickness are required. In this study microscale volume poly(3,4-ethylenedioxytiophene)-tosylate (PEDOT:Tos) layers are fabricated at the tip of a single mode optical fibre without the need for intermediate layers such as Indium Tin Oxide. This allows for optical interrogation (primarily at 1550 nm) of the properties and behaviour of PEDOT:Tos below thicknesses of 500 nm. The optical response (transmission and back-reflection) of the PEDOT:Tos obtained by exposure to different oxidant solu- tion is measured. The effect of different oxidant solution on conductivity, thermal conductivity and degradation time will be examined. This knowledge will lead to implications for the use of conducting polymers in sensing applications where an optical response is detected via a fibre.

The first detection of gravitational waves from a binary black hole inspiral by LIGO in September 2015 heralded the beginning of a new age in gravitational wave astronomy. The detection of a binary neutron inspiral in August 2017 and has now opened up a new era of multi-messenger astronomy. To increase the sensitivity of future gravitational wave detectors, a change to cryogenic silicon test masses and an increase in laser power may be required. Silicon is a compelling choice as it has high thermal conductivity at cryo- genic temperatures, which reduces temperature gradients generated by optical absorption. Additionally, at 123 K, its thermal expansion coefficient crosses zero. Thus, near this temperature, thermo-elastic distortion of the mirror surface should be drastically reduced, as would the effect of thermo-elastic noise due to thermodynamic temperature fluctuations. However, the adoption of silicon for the optical substrates would necessitate a shift of operating wavelength from 1064 nm to >1.3 μm where silicon is transparent. While potential wavelengths include ca. 1.55 μm and 2.0 μm, the longer wavelengths may be preferred due to lower scattering loss and coating absorption.

A microwave photonic true time delay line based on an integrated Kerr comb source with 49 GHz free spectral range was proposed and demonstrated. We theoretically analyze the performance of a phased array antenna and show that this large channel count results in a high angular resolution and wide beam-steering tunable range.

Hybrid integration of different materials will allow for different functionalities such as passive, amplifying, nonlinear, electro-optic, detection etc to build “system on a chip” devices. The vertically stacked layer design commonly proposed significantly increases the difficulty of the lithography process for the bottom-most layer due to the overlying topology. A methodology for significantly improving the fabrication tolerance of planar directional couplers is therefore presented. A parametric design study reveals that significant dimensional sensitivity improvements exist for certain center-to-center spacings for both power and wavelength splitters.

We study photonic circuits consisting of cold-atom ensembles coupled to light modes of optical nanofibres and long lengths of connecting or feedback fibres, such that the propagation time of light along these fibres is comparable to the timescale of the atomic dynamics. This provides a non-Markovian setting for quantum dynamics and feedback. The fibre-based platform enables implementation of a simple configuration for time-delayed quantum feedback where light emitted from the atoms propagates along a length of fibre and is reflected back towards the atoms by a fibre bragg grating (FBG). We will present the initial results of our experiments.

The optomechanical interaction between photonic and phononic waves in micron scale devices is increasingly becoming important for ultrasensitive force and mass sensing applications. Diamond is an exception material for the coupling of optical and mechanical modes because of the low absorption in visible spectrum and high mechanical modulus. To generate optomechanical coupling it is essential to achieve mechanical resonances in the GHz range. Previous work has shown that it is possible to achieve acoustic band gaps at such high frequencies by high-order band gaps which exploit periodic structures with novel topologies. In this work we investigate how the topology and geometry of the periodic structures influence the photon and phonon mode-confinement as well as the optomechanical coupling. By changing the topology and geometry of a unit cell structure based the properties of the targeted Bloch mode, both the resonant mode frequencies and the bandwidth can be tuned. The design method is able to achieve structures with quite large gap sizes for out-of-plane wave, in-plane wave, and the combined waves, which introduces more controllable mechanical modes in the cavity designs in diamond for strong coupling effects.

2D materials, led by graphene, have been widely explored in the last decade as saturable absorber (SA) materials. Most of this work has focussed on fibre compatible designs for use in fibre lasers (e.g. fibre connector sandwich, D-shaped fibre). Realising chip based mode locked lasers is an important challenge, and little work has been carried out on planar waveguide SAs, Here, simulation results for the absorption performance of two types of graphene based TeO2 waveguide SA designs with suitably high absorption and low saturation threshold are presented.

We report a method to improve the performance of unidimensional continuous-variable quantum key distribution with imperfect detector by adding a parameter-adjustable optical amplifier, where the optimal performance can approach the scenario with a perfect detector.

The ability to perform spatially resolved measurement of extreme temperatures, the order of 1000°C and above, would yield enormous benefit to many heavy industrial processes. While optical fibers can provide spatial information along their length through distributed and multi-point sensing techniques, operation at such temperatures is an area of ongoing research and development. A challenge is that conventional optical fibers, fabricated with a chemically doped core, suffer dopant diffusion at these high temperatures, ultimately limiting their operating lifespan. We can overcome this limitation by using specialty pure silica glass fibers, such as microstructured optical fibers. In this work we demonstrate the ability to use such fibers in a significantly multiplexed configuration with twenty fiber Bragg grating sensing elements written via femtosecond laser ablation.

There is growing demand for biodegradable polymer fibres in tissue engineering and nerve regeneration. We demonstrate a scalable and inexpensive fabrication technique to produce polycaproactone (PCL) fibres using fibredrawing technique. Here we report on the first successful drawing of hollow-core and solid-core PCL fibres of different cross sections. The demonstrated capacity to tailor the surface morphology of PCL fibres, together with their biodegradability and tissue compatibility, makes them a unique material base for tissue engineering and nerve regeneration applications.

We demonstrate a high-Q RF transversal filter based on a 49GHz-FSR integrated microcomb source that provides 80 taps across the C-band. By employing an on-chip micro-ring resonator, we generate a broadband Kerr comb with a large number of comb lines and use it as a high-quality multi-wavelength source. A Q factor of 73.7, an out-of-band rejection of 48.9 dB, and a wide tunable range are demonstrated. The experimental results verify the feasibility of our approach as a solution towards implementing highly reconfigurable MPFs with a large tap number and reduced system complexity.

Digital image correlation method is widely used in macro- and mesoscopic mechanical tests because of the advantages of non-contact, high precision, full field measurement, and simple experimental equipment. But it still has many shortcomings in theory and application. For example, the traditional DIC method has difficulty obtaining the desired result when the surface of the test object is rotated substantially or the deformation involves large rotation (i.e. measuring helicopter blade deformation dynamically). Some scholars argue that a rotation angle greater than 7° will not work with the DIC algorithm, and this phenomenon is called decorrelation [1-3]. The application of various nonlinear optimization algorithms greatly reduces the computation time of the DIC iteration process.

We experimentally demonstrate nanostructured silicon photodetectors which consist of subwavelength arrays of verticallyoriented waveguides etched into a P-I-N photodiode. Our device combines both spectral-filtering and photocurrentgeneration in one all-Si structure. We show that absorption and responsivity spectra of these nanophotonic devices can be tuned by appropriate geometric design.

We investigate distributed optical temperature sensors for continuous monitoring of temperature in the geophysical setting of the Alpine Fault located in the South Island of New Zealand. We interrogate the existing fibre-optic cables installed in the DFDP-2B borehole located in Whatoroa (893 m in depth) to accurately determine the temperature profile.

MIR sensing technology has the potential capacity to dramatically improve aspects of real-world problems - from planet formation to molecular species identification – once integrated “system on a chip” sensing devices are available at a palatable cost. A key limiter in achieving a full integrated on a chip design is the lack of broadband waveguide-based detectors, with no designs or experimental broadband devices having been demonstrated to date. Simulation and analysis conducted in this work has produced for the first time, practical graphene-based waveguide detector designs that can be made with existing and improved MIR waveguide technology. Using Rsoft FemSIM with high resolution graded gridding to accurately capture the effects in single layer graphene; extensive, and time consuming, parametrised simulations have been carried out for different waveguide designs to understand the design space available and optimise the absorption of light in graphene coated chalcogenide waveguides. The accuracy of the optical modelling and the values for the graphene material model were verified by modelling experimentally reported devices in the NIR region to ensure there is a close match to the measured points. Geometry (height, width), wavelength, waveguide type (Channel, Rib), Monolayer, bilayer and multilayer graphene layouts were the core variables investigated as functions of the waveguide core refractive index and top and bottom cladding indices. Fig. 1 give the examples of fully-etched waveguide design. Additionally, different materials as buffer/spacer layers to compress the field or to try and locate the graphene in a higher field region were also trialled. The results were contour graphs of absorption versus width and height for the fundamental mode at 10 different wavelengths with different Top/Bottom cladding index contrasts, from which it is possible to design wideband detectors.

We demonstrate a robust, stable and compact spectral filter for use in quantum optics experiments by implementing Fabry-Pérot resonators within optical fibre using pairs of fibre Bragg gratings. With only temperature stabilisation, these devices show less than 20 MHz frequency drift over 12 hours with a maximum suppression of roughly 35 dB and overall transmission of 75%. These characteristics make fibre Bragg grating Fabry-Pérot resonators ideal for quantum optics experiments where single photon-level signals must be efficiently filtered from large optical fields.

We have shown that it is possible to injection lock a pulsed Vertical Cavity Surface Emitting Laser (VCSEL). This is a cheap source of nanosecond pulsed light with a background noise of approximately ten percent. An inexpensive source of narrow-band pulsed light such as this could find many uses in quantum optics, such as the development of highbandwidth quantum memory.

We report on the development of a single frequency laser operating at a wavelength of 2.1 μm. This laser uses a holmium-doped distributed Bragg reflector (DBR) structure pumped at 1.15 μm. These lasers have applications in precision measurement, coherent laser radar and beam combination. Initial characterisation of the laser is included.

A line-based fiber optic sensor, modified from the loop-based configuration of the Sagnac interferometer using a Faraday rotator mirror (FRM), is easy to set the sensing fiber (SF) in the field application, especially in long-distance perimeter security. The sensor we proposed is composed of two line-based interferometers, which are multiplexed with super luminescent diode (SLD), interference unit (IU) and SF respectively through wavelength division multiplexer (WDM) to obtain different wavelength disturbance signals generated by the same disturbance. Two signals with fixed time delay, determined by the position of the disturbance and extracted by signal correlation method, are obtained. Then the position of disturbance can be calculated by it. Experiments show that low-frequency noise has a great impact on the positioning results, and even leads to the failure of positioning. In this work, the influence of disturbance frequency and sampling rate on the accuracy of calculation results is analyzed, and two new processing methods is proposed. Firstly, we use bandpass filtering to eliminate the effects of these factors. Disturbances at different locations require different filtering ranges. We propose a method to determine the filter range by null-frequency, which can achieve higher positioning accuracy. Secondly, the sampling rate of 0.5 MHz is raised to 2.5 MHz by using spline interpolation method. The combination of these two methods can achieve higher accuracy and better reliability of positioning results. Experiments results show that the positioning accuracy of this method can be improved from 200 m to 40 m with the total length of SF is 40 km.

Coupling light between optical components with different waveguide geometries on photonic integrated circuits have become an imperative function for many applications. Herein, we propose an algorithm for the design of low-reflection adiabatic optical components using a constant coupling approach. Low reflectivity is important for optical components that are in close proximity to semiconductor optical amplifiers, where a reflectivity of less than -50 dB is required. We apply the algorithm to a polarization mode converter on the silicon-on-insulator platform, where we reduce the back reflection from -41 dB to -58 dB. We also show the tradeoff between the reduction in the reflected power and the resulting device length.

This work reports the photoluminescence (PL) properties of Er doped AS2S3 films (at 0.1 mol% concentration) fabricated by RF co-sputtering. As sputtered films are shown to exhibit PL degradation only on exposure to the combination of green light and water vapour due to photo-incorporation of OH groups through film nanostructural pores. Rapid Thermal Annealing is investigated as a possible remedy to this issue.

Plasmonic colour filters are promising candidate for making colour filters in image sensors. Hexagonally arranged hole array based plasmonic colour filters in aluminium has several advantages for image sensor applications such as polarization insensitivity, CMOS compatibility and fine tuning of colours using a nanometer thick film. However, the hole array based filters are limited by their transmission efficiency (transmittance). This paper presents a new filling scheme of adding optimized extra coaxial holes in hole array to increase the transmittance. The results will have potential applications in CMOS and CCD image sensors, filter wheels, and submicron pixels development.

Driven by the growth trend of portable electronic products, the integration of functions into smaller electronic components (semiconductors) becomes more important, such as advanced packing. The fan-out type is the fastest growing advanced packaging platform. Re-Distribution Layers (RDL) are mainly structures in which the wafer lines are redistributed. In the process of RDL the residual film thickness in nanometers after Chemical-Mechanical Planarization (CMP) step and the depth of RDL structure are mainly the parameters should be measured to ensure the yield rate. In this research, we demonstrate an optical system design of microscope type spectral reflectometry which is based on finite microscope system with reflective objective. The advantage of finite microscope system is less optical components, which leads to less UV and NIR attenuation for the purpose of thin film (~5 nm) and thick film (~100 μm) measurement. Adjustable illumination angle design is also included. The illumination light incident on the sample are designed as parallel as possible for increasing the reflective light rays from bottom of RDL. The spot size of measurement area is ~13 μm in diameter. Meanwhile, the corresponding algorithm including thin film interference model fitting and Discrete Fourier Transform (DFT) for high density RDL analysis are presented. Our non-destructive solution can measure thin film as thin as 5 nm and the depth of high density RDL with line width/ space = 1 μm/ 1μm. Metrology results from RDL structure and SiO2/Si standard reference material are presented.

We propose the feasible design of a device that can offer a unique method for controlling the terahertz spectrum allocation, exploiting existing photonics-based technologies. We successfully designed a multiplexer and demultiplexer using arrayed waveguide grating, where the device can multiplex and demultiplex four frequency channels (8.64 GHz bandwidth) in the same operating range defined by the IEEE 802.15.3d standard with at least 10 dB separation. This study reveals that proposed solution play a major role in maturing the next generation wireless communication (beyond 100 GHz) networks.

We introduce a new approach to infrared microspectroscopy – Optical-Photothermal Infrared (O-PTIR) Spectroscopy. Based on the principles of the photothermal effect (in response to IR radiation), we describe and illustrate how the novel use of an optical probe (532nm laser) enables significant enhancements in IR micro-spectroscopy, with ~20x improvement in spatial resolution compared to traditional IR microscopes (FTIR or direct QCL). Furthermore, this configuration enables the generally preferred and practical reflection (far-field) mode analysis without exhibiting any scatter artefacts and poor SNR of traditional systems, with O-PTIR reflection spectra being equivalent to FTIR transmission spectra. Due to the unique systems architecture, namely, the use of a visible probe beam to extract IR spectroscopic information, we show how this same visible laser can be used simultaneously as a Raman excitation source, thus delivering IR and Raman microspectroscopy from the same spot at the same time with the same spatial resolution. As a performance proof, IR spatial resolution of 400nm across a polymer interface has been obtained, together with 900nm single polymeric particle detection from a microplastics model system from a dried saline solution. Reflection mode fiber analysis of 10 micron and 800nm fibers shows reflection spectra are unaffected by fiber diameter to produce high quality FTIR-transmission mode comparable data. Finally, we demonstrate live cell (epithelial cheek cells) IR spectroscopic imaging analysis in water with submicron intracellular resolution.

With the development of high-speed digital system, high-speed serial data transmission is widely used and the FPGA containing high-speed serial transceiver is also widely used. The high-speed serial interface of Xilinx's FPGA includes GTP, GTX, GTH and other high-speed transceivers with different transmission rate. The physical transmission speed of these transceivers can reach tens of Gbps. These low-level high-speed transceivers can support a variety of top-level transmission protocols, such as SRIO, PCIE, SATA, optical fiber and so on. Among these top-level transmission protocols, optical fiber transmission has the longest transmission distance and is widely used in various scenarios. Optical fiber transmission has three advantages. Firstly, its transmission capacity is very large and it can support ultralong distance transmission, one line optical fiber transmission rate can easily reach several Gbps. Secondly, optical fiber communication has strong anti-electromagnetic interference characteristics, which can ensure the quality of data transmission. Thirdly, optical fiber transmission uses light wave for data transmission and the light wave transmitted in the optical fiber cannot run out, so there is no radiation and it is difficult to eavesdrop.

We report a new measurement for the 413 nm tune-out wavelength for metastable helium (He*); the optical wavelength at which the light does not interact with the atom, whose accurate determination provides a sensitive test of QED independent of transition energy measurements. Mitroy and Tang have shown[1] that the 413nm tune-out wavelength of the metastable 2³S₁ state of helium is particularly sensitive to QED effects, and a measurement of this tune-out to 175MHz accuracy would constitute the most precise measurement of transition rate information made in Helium.

Spontaneous symmetry breaking (SSB) is a ubiquitous natural phenomenon where a system characterized by certain symmetries can evolve into a state that does not exhibit those symmetries. SSB underpins many fundamental phenomena, including phase transitions in meta-materials or Bose-Einstein condensates, the emergence of the Nambu-Goldstone and Higgs modes of crucial importance in particle physics, or bifurcations in lasers, and could have significant applications, especially in photonics. Physical systems however often exhibit deviations from perfect symmetry because of naturally occurring imperfections. How small asymmetries affect SSB-related dynamics is therefore an important problem. Surprisingly, this has barely been considered in experiments, and even then restricted to situations with only one asymmetry parameter. Here, we report spontaneous breaking of a mirror symmetry in an optical experiment with two controllable asymmetry parameters. Specifically, we explore how controlled asymmetries affect the range of co-existence of two homogeneous states (HSs) with different polarizations in a driven Kerr resonator, and discover that different asymmetries can compensate for each other. In particular, we show that we can restore a standard pitchfork-like response characteristics of SSB under asymmetric conditions.

The highly efficient modulation of the luminescence from upconversion nanoparticles combined with graphene oxide in a thin film was achieved at a millisecond timescale through the photochemical reduction of graphene oxide under UV irradiation. The experimental design comprised the integration of the upconversion nanoparticles with graphene oxide to form a reproducible and scalable thin film. This design enabled convenient testing of the sample with a home‐built optical system setup comprising an UV CW laser at 375 nm for the photochemical reduction of graphene oxide and a near-infrared CW laser at 980 nm for the excitation of the upconversion nanoparticles. The recovery of the graphene‐like structure through the photochemical reduction of graphene oxide was accompanied by a variation in the absorption coefficient of the thin film, which enabled super‐quenching of the luminescence from the upconversion nanoparticles under near‐infrared excitation with values of up to ~90%. Further, the instantaneous reduction in the intensity upon UV irradiation offered decreased modulation time of upconversion luminescence down to milliseconds at microwatt‐level power. Optical patterning was successfully produced in the thin film: representations of a leaf, the Sydney Opera House and a kangaroo were fabricated in the thin film and recovered by raster scanning the sample. The resulting patterns had high spatial resolution for upconversion luminescence modulation down to the diffraction limit for the considered wavelengths. These findings pave the way toward prompt use of this novel thin film for display technologies, photoswitching in optoelectronic devices, and optical data storage applications.