This PDF file contains the front matter associated with SPIE Proceedings Volume 10106, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

One of the key challenges in the field of silicon photonics remains the development of compact integrated light sources. In one approach, rare-earth-doped glass microtoroid and microdisk lasers have been integrated on silicon and exhibit ultra-low thresholds. However, such resonator structures are isolated on the chip surface and require an external fiber to couple light to and from the cavity. Here, we review our recent work on monolithically integrated rare-earth-doped aluminum oxide microcavity lasers on silicon. The microlasers are enabled by a novel high-Q cavity design, which includes a co-integrated silicon nitride bus waveguide and a silicon dioxide trench filled with rare-earth-doped aluminum oxide. In passive (undoped) microresonators we measure internal quality factors as high as 3.8 × 105 at 0.98 µm and 5.7 × 105 at 1.5 µm. In ytterbium, erbium, and thulium-doped microcavities with diameters ranging from 80 to 200 µm we show lasing at 1.0, 1.5 and 1.9 µm, respectively. We observe sub-milliwatt lasing thresholds, approximately 10 times lower than previously demonstrated in monolithic rare-earth-doped lasers on silicon. The entire fabrication process, which includes post-processing deposition of the gain medium, is silicon-compatible and allows for integration with other silicon-based photonic devices. Applications of such rare earth microlasers in communications and sensing and recent design enhancements will be discussed.

The development of optically confined structure is a major topic in both basic and applied physics not solely ICT oriented but also concerning lighting, laser, sensing, energy, environment, biological and medical sciences, and quantum optics. Glasses and glass-ceramics activated by rare earth ions are the bricks of such structures. Glass-ceramics are nanocomposite systems that exhibit specific morphologic, structural and spectroscopic properties allowing developing new physical concepts, for instance the mechanism related to the transparency, as well as novel photonic devices based on the enhancement of the luminescence. The dependence of the final product on the specific parent glass and on the fabrication protocol still remain an important task of the research in material science. Looking to application, the enhanced spectroscopic properties typical of glass ceramic in respect to those of the amorphous structures constitute an important point for the development of integrated optics devices, including optical amplifiers, monolithic waveguide laser, novel sensors, coating of spherical microresonators, and up and down converters. This paper presents some results obtained by our consortium regarding glass-based photonics systems. We will comment the energy transfer mechanism in transparent glass ceramics taking as examples the up and down conversion systems and the role of SnO₂ nanocrystals as sensitizers. Coating of spherical resonators by glass ceramics, 1D-Photonic Crystals for luminescence enhancement, laser action and disordered 1-D photonic structures will be also discussed. Finally, RF-Sputtered rare earth doped P₂O₅- SiO₂-Al₂O₃-Na₂O-Er₂O₃ planar waveguides, will be presented.

We report the spectroscopy of crystalline waveguide amplifiers operating in the telecom C-band. Thin films of erbiumdoped gadolinium lutetium potassium double tungstate, KGd_xLu_yEr_1-x-y (WO₄)₂, are grown by liquid- phase epitaxy onto undoped potassium yttrium double tungstate (KYW) substrates and micro-structured by Ar⁺- beam etching. Channel waveguides with erbium concentrations between 0.45–6.35 × 10²⁰ cm^-3 are characterized. The transition cross-sections of interest are estimated. The effect of energy-transfer up-conversion (ETU) is experimentally investigated. Microscopic and macroscopic ETU parameters are extracted from a simultaneous analysis of 20 decay curves of luminescence on the transition ⁴I_13/2 → ⁴I_13/2. The correlation between ETU and the doping concentration is studied. Pump excited-state absorption (ESA) on the transition ⁴I_11/2 → ⁴F_7/2 is investigated via a direct ESA measurement using a double-modulation pump-probe technique. The effect of ESA is studied for different pump wavelengths. The pump wavelength of 984.5 nm is found to be favorable for the complete range of erbium concentrations.

In this work, we propose the realization of two single mode distributed feedback (DFB) lasers emitting at 1.5μm with ultra-narrow linewidths, co-integrated on a co-doped Erbium Ytterbium IOG1¹ glass substrate. The beating note of these two lasers on a fast photodiode is used to generate mm-wave signals. Each laser is composed of a waveguide fabricated by ion exchange with a Bragg grating etched on the top. In order to set a precise value of the mm-wave frequency, the emission wavelength of both DFB lasers must be accurately fixed. This is achieved by controlling the laser’s waveguide design. The beating produced between these lasers generates mm-wave signals from GHz to THz. The co-integration helps to enhance the beating quality by reducing fluctuations between the two lasers. Lasers are first studied independently: their optical power, linewidth and relative intensity noise are characterized. Finally, the beating signal quality is estimated through the characterization of the produced electrical spectrum.

Ytterbium-doped potassium rare-earth double tungstate thin films are excellent candidates for highly efficient waveguide lasers, as well as high-gain waveguide amplifiers, with a record-high optical gain per unit length of 935 dB/cm recently demonstrated. However, the spectroscopic properties of these highly ytterbium-doped thin films and, in particular, their temperature dependence are not well investigated. These characteristics are required for the understanding of the behavior of the fabricated optical devices and crucial for further device optimization. We experimentally determined the absorption cross-sections for a potassium ytterbium gadolinium double tungstate, KYb_0.57Gd_0.43(WO₄)₂, thin film grown lattice matched onto an undoped KY(WO₄)₂ substrate. At room temperature, the peak cross-section value at 981 nm and the overall absorption spectrum are very similar to those of Yb-doped bulk potassium double tungstate crystals, although Yb is now the dominating rare-earth content. The temperature-dependent study shows a significant decrease of the absorption cross-section values at 933 nm and 981 nm with increasing temperature. We verify theoretically that this is due to the temperature dependence of fractional populations in the individual Stark levels of the absorbing crystal-field multiplet, in combination with the linewidth broadening with increasing temperature. Further investigations suggest that the broadening of absorption linewidth at 981 nm originates in the intra-manifold relaxation between the two lowest Stark levels of the ground state. Finally, the implications of the spectroscopic findings on the operating characteristics of waveguide amplifiers are investigated. Amplifiers operating at 80 °C are expected to exhibit only 67% of the maximum theoretical gain at room temperature.

Phase sensitive amplification (PSA) is an attractive technology for integrated all-optical signal processing, due to it's potential for noiseless amplification, phase regeneration and generation of squeezed light. In this talk I will review our results on implementing four-wave-mixing based PSA inside integrated photonic devices. In particular I will discuss PSA in chalcogenide ridge waveguides and silicon slow-light photonic crystals. We achieve PSA in both pump- and signal-degenerate schemes with maximum extinction ratios of 11 (silicon) and 18 (chalcogenide) dB. I will further discuss the influence of two-photon absorption and free carrier effects on the performance of silicon-based PSAs.

In this communication, authors report for the first time on the fabrication and testing of Si₃N₄ non-linear photonic circuits for CMOS-compatible monolithic co-integration with silicon-based optoelectronics. In particular, a novel process has been developed to fabricate low-loss crack-free Si₃N₄ 750-nm-thick films for Kerr-based nonlinear functions featuring full thermal budget compatibility with existing Silicon photonics and front-end Si optoelectronics. Briefly, differently from previous and state-of-the-art works, our nonlinear nitride-based platform has been realized without resorting to commonly-used high-temperature annealing (~1200°C) of the film and its silica upper-cladding used to break N-H bonds otherwise causing absorption in the C-band and destroying its nonlinear functionality. Furthermore, no complex and fabrication-intolerant Damascene process - as recently reported earlier this year - aimed at controlling cracks generated in thick tensile-strained Si₃N₄ films has been used as well. Instead, a tailored Si₃N₄ multiple-step film deposition in 200-mm LPCVD-based reactor and subsequent low-temperature (400°C) PECVD oxide encapsulation have been used to fabricate the nonlinear micro-resonant circuits aiming at generating optical frequency combs via optical parametric oscillators (OPOs), thus allowing the monolithic co-integration of such nonlinear functions on existing CMOS-compatible optoelectronics, for both active and passive components such as, for instance, silicon modulators and wavelength (de-)multiplexers. Experimental evidence based on wafer-level statistics show nitride-based 112-μm-radius ring resonators using such low-temperature crack-free nitride film exhibiting quality factors exceeding Q >3 x 10⁵, thus paving the way to low-threshold power-efficient Kerr-based comb sources and dissipative temporal solitons in the C-band featuring full thermal processing compatibility with Si photonic integrated circuits (Si-PICs).

Chalcogenide glass (ChG) which contain one or more chalcogen elements is one of the most interesting material for infrared (IR) photonics owing to its unique optical properties, such as high refractive index, strong optical nonlinearity, and wide infrared transparency. In this paper, we experimentally demonstrate high-quality ChG micro-disk resonators on oxidized silicon wafers fabricated by the standard UV photolithography and lift-off. Quality factor of micro-disk resonators are often limited by optical scattering loss induced by lithographically defined edge roughness. Thermal reflow of chalcogenide itself may significantly reduce edge roughness, but thermal shrinkage and deformation of the material during the reflow make it hard to precisely control the overall size and shape of the fabricated device. Instead, we reduce the sidewall roughness using thermal reflow of photoresist and modified bi-layer lift-off process. Typically, the thermal reflow of resist destroys the undercut or vertical sidewall profile of developed resist layer, making it extremely difficult or impossible to subsequently use lift-off or etching for patterning. We address this issue by first wet etching the silica substrate to undercut the reflowed photoresist, creating an overhang required for lift-off. ChG film is then deposited to produce a micro-disk resonator with much improved edge roughness. To finally create a micro-disk resonator on a silica pillar, we adopt vapor etching of the silica substrate. With optimized conditions of reflow and undercut, we obtained high quality ChG disk-resonators with extremely smooth edge profile, operating in the infrared region. Complete characterization results will be presented at the conference. The new method is compatible with traditional CMOS process and thus expected to have great potentials for fabricating high quality photonic integrated devices.

In this paper, we analytically describe the parametric amplification in ring resonators using silicon and silicon nitride waveguides. Achievable gain and bandwidth of the ring-based amplifiers are studied taking into account the Kerr nonlinearity for silicon nitride and Kerr nonlinearity as well as two photon absorption and free carrier absorption for silicon waveguides. Both telecom and 2-μm wavelengths are investigated in case of silicon. An approach for obtaining the optimum amplifier design without initiating the comb generation has been introduced. It is shown that there is a trade-off between the input pump and amplifier bandwidth. It is estimated that using optimum designs an amplifier with a gain and bandwidth of 10 dB and 10 GHz could be feasible with silicon ring resonators in 2 μm.

Traditionally, bulk lithium niobate has primarily been used in surface acoustic wave devices and optical modulators, with its use in optics limited primarily by the lack of a method of creating low loss, high index waveguides. Thin film single crystal lithium niobate-on-insulator is a promising platform for future applications in integrated optics due to the availability of a strong electro-optic effect in this material, however. We have fabricated and characterized low-loss waveguides (< 5 dB/cm), ring and racetrack resonators, and other structures in this material system that could potentially be useful in future applications.

The ubiquitous need for compact, low-cost and mass production photonic devices, for next generation photonic enabled applications, necessitates the development of integrated components exhibiting functionalities that are, to date, carried out by free space elements or standard fiber equipment. The polarization rotator is a typical example of such tendency, as it is a crucial part of the PBS operation of future transceiver modules that leverage polarization multiplexing schemes for increasing the optical network capacity. Up to now, a variety of integrated polarization rotating concepts has been proposed and reported, relying, mainly, on special waveguide crossection configurations for achieving the rotation. Nevertheless, most of those concepts employ SiPh or III-V integration platforms, significantly increasing the fabrication complexity required for customizing the waveguide crossection, which in turn leads to either prohibitively increased cost or compromised quality and performance. In this manuscript we demonstrate the extensive design of a low-cost integrated polymer polarization rotator employing a right-trapezoidal waveguide interfaced to standard square polymer waveguides. First the crossection of the waveguide is defined by calculating and analyzing the components of the hybrid modes excited in the waveguide structure, using a Finite Difference mode solver. Mode overlaps between the fundamental polymer mode and each hybrid mode reveal the optimum lateral offset between the square polymer and the trapezoidal waveguide that ensures both minimum interface loss and maximized polarization rotation performance. The required trapezoidal waveguide length is obtained through EigenMode Expansion (EME) propagation simulations, while more than 95% maximum theoretical conversion efficiency is reported over the entire C-band, resulting to more than 13dB polarization extinction ratio. The polarization rotator design relies on the development of angled polymer waveguide sidewalls, employing the tilted laser ablation technology, currently available at CMST. Therefore, the aforementioned simulation steps adhere fully to the respective design rules, taking into account the anticipated fabrication variations

Theoretical analysis of the modulation performance of this wave-guide device shows great potential when combined with a single-mode laser on a monolithic optical chip. On the basis of the reversed-bias electro-optic effect, modulation speeds surmounting 25 Gbit/s with 10 dB extinction ratio are feasible.

A photonic lantern is an adiabatic guided-wave transition between a multimode waveguide and a set of single-mode cores. As such, photonic lanterns facilitate the efficient coupling of multimode light to single-mode devices, examples of which include fibre Bragg gratings and arrayed waveguide gratings. In this work, we demonstrate that photonic lanterns based on tapered multicore fibres (MCFs) provide a potentially powerful new route to efficiently couple multimode states of light to a two-dimensional array of Single Photon Avalanche Detectors (SPADs). The SPAD array consists of a 32×32 square array of pixels, each of which has its own time to digital converter (TDC) for Time Correlated Single Photon Counting (TCSPC) with a timing resolution of 55 ps. For our application, the geometry of the MCF used to fabricate the photonic lantern was chosen such that each single mode in the MCF can be mapped onto an individual SPAD pixel. Upon injecting a broad supercontinuum signal into a 290 m long MCF via a photonic lantern, wavelength-to-time mapped spectra were obtained from all modes. We believe that the techniques we report here may find applications in areas such as Raman spectroscopy, coherent LIDAR, and quantum optics.

In this work, we demonstrate the first stress-optic modulator in a silicon nitride-based waveguide platform (TriPleX) in the telecommunication C-band. In our stress-optic phase modulator the refractive index of the waveguiding materials is controlled by the stress-optic effect induced by actuating a 2 μm thick PZT layer on top of the TriPleX waveguide geometry. The efficiency of the modulator is optimized by, amongst others, focusing the applied stress in the waveguide core region through a local increase of the top cladding. Using a Mach-Zehnder interferometer, we measured a half-wave voltage, V_π, at 34 V at a wavelength of 1550 nm using a modulator with a total length of 14.8 mm. The measured static power consumption of our stress-optic modulator is in the μW-region as it is only determined by small leakage currents (< 0.1 μA), while the dynamic power consumption at a rise time of 1 ms (1 kHz excitation) is less than 4 mW per modulator. The stress optical modulator goes with an excess loss of 0.01 dB per modulator only. This is in line with the typical low loss characteristics of TriPleX waveguides, being < 0.1 dB/cm at a wavelength of 1550 nm. These specifications make stress-optic modulators an excellent choice for next generation optical beam forming networks with a large number of actuators in silicon photonics in general and in the TriPleX platform in particular.

We report on our recent advances on integrated hybrid InP/SOI transmitters using the Silicon Photonic fabrication technology. We demonstrate the direct modulation at 10 Gbits/s of different laser configurations such as wavelength tunable lasers, Distributed FeedBack (DFB) lasers and Chirp Managed Lasers (CMLs). We will also present the design, fabrication and characterization of various hybrid InP/SOI transmitters integrating lasers (tunable or DFB) and modulators (silicon or III-V) with modulation up to 32 Gbits/s.

In this paper, the 200mm silicon-on-insulator (SOI) platform is used to demonstrate the monolithic co-integration of hybrid III-V/silicon Distributed Bragg Reflector (DBR) tunable lasers and silicon Mach-Zehnder modulator (MZMs), to achieve fully integrated hybrid transmitters for silicon photonics. The design of each active component, as well as the fabrication process steps of the whole architecture are described in details. Data transmission rate up to 25Gb/s has been reached for transmitters using MZMs with active lengths of 2mm and 4mm. Extinction ratios of respectively 2.9dB and 4.7dB are obtained by applying drive voltages of 2.5V peak-to-peak on the MZMs. 25Gb/s data transmission is demonstrated at 1303.5nm and 1315.8nm, with the possibility to tune the operating wavelength by up to 8.5nm in each case, by using metallic heaters above the lasers Bragg reflectors.

A photonic integrated signal processor based on the InP-InGaAsP material system consisting of a bypass waveguide and three mutually-coupled micro rings with each ring having two semiconductor optical amplifiers (SOAs) and a current-injection phase modulator (PM) for ultra-wideband signal processing and microwave signal generation is discussed. The signal processor can be reconfigured to perform signal processing functions including temporal differentiation, and temporal integration. The reconfigurability is achieved by controlling the coupling between the rings and the bypass waveguide by a multi-mode interference (MMI) Mach-Zehnder interferometer (MZI) coupler and the injection currents to the SOAs. The current injection PM in a ring is used for wavelength tuning. In addition to signal processing, the signal processor can also be reconfigured to operate as a microwave signal generator. The generation a linearly chirped microwave waveform is discussed.

In recent years, microbottle resonators that support non-degenerate whispering gallery modes (WGMs), propagating by successive total internal reflections close to the resonator surface and all along its axis, have been widely investigated due to their potential applications in optical sensing, microlasers and nonlinear optics. To overcome some drawbacks of the standard silica microbottle resonators, we focused our attention on polymers such as SU-8 resist and NOA resins. A drop of polymeric material is dispensed onto a fiber stem, providing a mechanical support for the bottle resonator, and is photo-polymerized by an UV lamp. The interrogation system, usually constituted by a tapered silica fiber evanescently coupled with the microresonator, is substituted by a more stable planar waveguide realized in SU-8 by means of standard photolithography technique. Moreover, for guarantying the stability to surrounding disturbance of the coupling between the microbottle resonator and the planar waveguide, the fiber stem is glued to substrate. Two drilled holes in the substrate allow the rise of the glue at the ends of the fiber stem and the fixing of sensor on PMMA substrate. In the present work, we presented an integrated full polymeric platform with self-assembled bottle microresonators packaged in a stable structure. SU-8 and NOA based microbottles are realized and morphologically characterized. The low autofluorescence emission and long term stability make the NOA based bottles suitable to be employed in a great variety of conditions. Bulk sensing measurements are performed by using water:ethanol solutions and a bulk sensitivity of 120 nm/RIU is estimated.

We report on the fabrication and characterization of Bragg gratings in UV-NIL structured Ormocer hybrid polymer rib-type waveguides using phase mask technology. The influence of fabrication parameters such as the applied laser fluence during the inscription process and the grating's length on the spectral behavior of the waveguide Bragg gratings was experimentally determined and compared to numerical simulations and calculations. To investigate potential sensor applications, the sensitivity of the thus fabricated optical devices towards refractive index changes of the gratings' surrounding (qualification for bio- and chemical sensing) as well as the sensitivity towards temperature and relative humidity were determined.

In this work, we demonstrate centimeter-long Mach-Zehnder interferometers (MZIs) suitable for optical uid sensing applications, fabricated on a silicon-on-insulator platform through photolithography. The sensing mech- anism is based on the perturbation of the evanescent field of the optical mode in the sensing arm of the MZI by the measurand. We explore two different configurations for the MZI sensing arm, a partially exposed and a fully suspended, both defined as ridge waveguides with a 450 nm-wide and a 220 nm-thick ridge on a 90 nm-thick silicon slab. The partially exposed MZI arm has oxide under-cladding and air over-cladding, while the fully suspended version has its buried oxide locally removed through an isotropic etch. The MZIs are slightly unbalanced, with arm lengths around 1 cm. The sensitivity of the devices is evaluated through mode solver simulations, with values around 240 nm/RIU and 740 nm/RIU, for the partially exposed and fully suspended structures, respectively.

Sensors based on optical waveguides for chemical sensing have attracted increasing interest over the last two decades, fueled by potential applications in commercial lab-on-a-chip devices for medical and food safety industries. Even though the early studies were oriented for single-point detection, progress in device size reduction and device yield afforded by photonics foundries have opened the opportunity for distributed dynamic chemical sensing at the microscale. This will allow researchers to follow the dynamics of chemical species in field of microbiology, and microchemistry, with a complementary method to current technologies based on microfluorescence and hyperspectral imaging. The study of the chemical dynamics at the surface of photoelectrodes in water splitting cells are a good candidate to benefit from such optochemical sensing devices that includes a photonic integrated circuit (PIC) with multiple sensors for real-time detection and spatial mapping of chemical species. In this project, we present experimental results on a prototype integrated optical system for chemical mapping based on the interaction of cascaded resonant optical devices, spatially covered with chemically sensitive polymers and plasmon-enhanced nanostructured metal/metal-oxide claddings offering chemical selectivity in a pixelated surface. In order to achieve a compact footprint, the prototype is based in a silicon photonics platform. A discussion on the relative merits of a photonic platform based on large bandgap metal oxides and nitrides which have higher chemical resistance than silicon is also presented.

The change in the optical properties of VO₂ across its insulator to metal to transition could give rise to novel photonic devices with beyond state-of-the art performance in terms of footprint, power consumption and speed operation. However, the final performance strongly depends on the control and efficiency of the phase transition in the VO₂. For electro-optical applications, such control and efficiency is highly dependent on the electrode configuration. In this work, the influence of the electrodes is experimentally analyzed and an alternative approach is proposed to switch the VO₂ to the metallic state by minimizing the electrical power consumption. The electro-optical performance of the proposed short-circuited electrode is also experimentally demonstrated. An extinction ratio of 12 dB is achieved with a 20μm long hybrid VO₂/Si waveguide with an electrical power of only 11mW. The power consumption could be further reduced by decreasing the distance between the electrode and the silicon waveguide, which in this work has been fixed to 1.5μm, without affecting the optical losses.

In this paper a generic monolithic photonic integration technology platform and tunable laser devices for gas sensing applications at 2 μm will be presented. The basic set of long wavelength optical functions which is fundamental for a generic photonic integration approach is realized using planar, but-joint, active-passive integration on indium phosphide substrate with active components based on strained InGaAs quantum wells. Using this limited set of basic building blocks a novel geometry, widely tunable laser source was designed and fabricated within the first long wavelength multiproject wafer run. The fabricated laser operates around 2027 nm, covers a record tuning range of 31 nm and is successfully employed in absorption measurements of carbon dioxide. These results demonstrate a fully functional long wavelength photonic integrated circuit that operates at these wavelengths. Moreover, the process steps and material system used for the long wavelength technology are almost identical to the ones which are used in the technology process at 1.5μm which makes it straightforward and hassle-free to transfer to the photonic foundries with existing fabrication lines. The changes from the 1550 nm technology and the trade-offs made in the building block design and layer stack will be discussed.

Si3N4 grown by low pressure chemical vapor deposition (LPCVD) on thermally oxidized silicon wafers is largely utilized for creating integrated photonic devices due to its ultra-low propagation loss and large transparency window (400 nm to 2350 nm). In this paper, an ultra-low-loss and broadband mode converter for monolithic integration of different materials onto the passive Si₃N₄ photonic technology platform is presented. The mode size converter is constructed with a vertically tapered Si₃N₄ waveguide that is then buried by a polymer or an Al₂O₃ waveguide. The influence of the various design parameters on the converter characteristics are investigated. Optimal designs are proposed, in which the thickness of the Si₃N₄ waveguide is tapered from 200 nm to ~40 nm. The calculated losses of the mode converters at 976 nm and 1550 nm wavelengths are well below 0.1 dB for the Si₃N₄-polymer coupler and below 0.3 dB for the Si₃N₄-Al₂O₃ coupler. The preliminary experimental results show good agreement with the design values, indicating that the mode converters can be utilized for the low-loss integration of different materials.

Widespread deployment of silicon photonics will benefit strongly from improved high-port-density interconnect solutions between chips, interposers, and other waveguide fabrics. We present an adiabatic silicon waveguide to polymer waveguide coupler design incorporating strong vertical asymmetries offering high efficiency, small footprint, and improved tolerance to lateral misalignment. The design incorporates a standard 450nm-wide silicon waveguide tapered down to 50nm over a distance of 200μm with a 1.6μm-thick polymer waveguide having a 4μm-wide core atop the taper. The coupler exhibits <0.1dB loss for both TE and TM modes based on 3-dimensional finite element modeling. Moreover, the modeled device exhibits less than 0.1dB excess loss with lateral misalignment of +/–2μm between polymer and silicon waveguide for TE mode, and 0.2dB excess loss with +/–1.6μm offset for the TM mode, and 1dB excess loss for both TE and TM modes with +/–2.7μm misalignment. This taper design should enable reduction in manufacturing costs due to a reduced on-chip footprint and the potential for lower-precision, higher-throughput assembly tools. The authors would like to acknowledge the support of AIM Photonics. This material is based on research sponsored by Air Force Research Laboratory under agreement number FA8650-15-2-5220. The U.S. Government is authorized to reproduce and distribute reprints for Governmental purposes notwithstanding any copyright notation thereon. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of Air Force Research Laboratory or the U.S. Government.

Silicon photonics is rapidly emerging as a mature technology platform for the fabrication of photonic integrated circuits. It builds on the technology base of the CMOS-world and allows to implement advanced photonic functions on a small footprint chip with high accuracy and yield. For operation at telecom wavelengths above 1 micrometer one typically uses silicon-on-insulator wafers with waveguides with a silicon core. For short-wavelength operation, below 1 micrometer, one can use a silicon nitride (SiN) core instead of a silicon core. This results in a platform for operation in the visible and near infrared, with moderately high refractive index contrast and low loss photonic components. Operation at short wavelengths can be beneficial for a variety of reasons, including the possibility to use low cost high performance sources and detectors and the compatibility with sensing in an aqeous environment. The SiN CMOS-platform has been used to demonstrate a variety of spectroscopic sensing functions. In essence the SiN chips may contain sensing structures, whereby the evanescent tail of the guided light is interacting with the analyte, as well as spectrometric functions to read out the spectrum resulting from the interaction with the analyte. This approach has allowed to demonstrate refractive index biosensors, spontaneous Raman spectroscopy and surface-enhanced Raman spectroscopy. In the latter case the SiN waveguides are enriched with gold nano-antennas to enhance the local field strength seen by the analyte. The spectrometric functions can be based on arrayed waveguide gratings, echelle grating spectrometers or Fourier Transform spectrometers.

Research in nuclear safety and fuel reprocessing has led to a surging need for novel chemical analysis tools with reduced analyte and effluent volumes. Recent technological advances for the elaboration and packaging of glass optofluidic co - integrated sensors have opened up the way for said analysis in harsh environments. We discuss a sensor engineering approach for the construction of an integrated absorption spectrometer with an ion-exchange core. Pu(VI) oxidation state exhibits a major absorption peak at a wavelength of 831 nm with a molar absorption coefficient of 545 L.mol^-1.cm^-1. An evanescent waveguiding sensing structure that allows guided fluid/light interaction is investigated in order to provide absorption spectroscopy measurements. The work presented consists of optical simulations as well as experimental measurements. Waveguide engineering with respects to modal transmission, field/fluid interaction coefficient Γ and device losses is presented. The simulations are carried out by computing ion-exchanged waveguide refractive index distribution and using it in mode solver software. Device optical characterization and bench tests are carried out to verify approach viability. First device measurements of a neodymium absorption peak in nuclear manipulation conditions are displayed.

Integrated silicon photonics promises efficient on-chip solutions for chemical and bio-molecule sensing for faster and reliable disease diagnostics. By integrating a sensor with a light source and a detector, a compact lab-on-chip sensing device is possible to realize. To increase the sensing efficiency, slot waveguide geometry is preferable due to the high confinement of the mode within the cover material. When two different light-paths in a structure interfere with each other, causing the superposition of a Lorenzian response with the background radiation continuum, a Fano lineshape occurs. This sharp resonance leads to a superior refractive index sensing capability. To develop a compact on-chip Fano-resonant platform for chemical sensing, we used a merged photonic crystal – slot waveguide (MPCSW) structure as the basic building block. It contains slot waveguides merged with Bragg gratings, formed by periodic patterning of the rails. A defect between the two Bragg grating sections forms a resonant cavity. In addition to the enhancement due to the confinement of light in the slot waveguide, the highly dispersive nature of the Bragg grating leads to slow light effect at the resonance. Three MPCSW structures are parallel-coupled to form an on-chip Fano system. By changing the refractive index of the cover material, we found a sensitivity as high as 775 nm/RIU. Moreover, the group index at the resonance of our Fano system is as high as ng = 500, due to the effect of slow light. We obtain vast increase in the refractive index sensitivity of the device.

In this work, a silicon oxynitride-on-silica refractometer is presented, based on sub-wavelength coupled arrayed waveguide interference, and capable of low-cost, high resolution, large scale deployment. The sensor has an experimental spectral sensitivity as high as 3200 nm/RIU, covering refractive indices ranging from 1 (air) up to 1.43 (oils). The sensor readout can be performed by standard spectrometers techniques of by pattern projection onto a camera, followed by optical pattern recognition. Positive identification of the refractive index of an unknown species is obtained by pattern cross-correlation with a look-up calibration table based algorithm. Given the lower contrast between core and cladding in such devices, higher mode overlap with single mode fiber is achieved, leading to a larger coupling efficiency and more relaxed alignment requirements as compared to silicon photonics platform. Also, the optical transparency of the sensor in the visible range allows the operation with light sources and camera detectors in the visible range, of much lower capital costs for a complete sensor system. Furthermore, the choice of refractive indices of core and cladding in the sensor head with integrated readout, allows the fabrication of the same device in polymers, for mass-production replication of disposable sensors.

The objective of this work was to develop an integrated general purpose label-free optical sensor using standard photolithography on silicon-on-insulator platform for lab on chip applications. Shallow silicon waveguides have weak confinement in the silicon with lots of field in the cladding. This is advantageous in sensor applications due to the high light matter interaction. Here, we use our shallow strip waveguide platform to design a sensor employing a multimode interference (MMI) section. Utilizing a multi-mode section as short as 4 mm, the sensor exhibits sensitivity ranging from 417 nm / RIU to 427 nm / RIU with a figure of merit from 32 to 133.

With the recent progress in integrated silicon photonics technology and the recent development of efficient quantum cascade laser technology (QCL), there is now a very good opportunity to investigate new gas sensors offering both very high sensitivity, high selectivity (multi-gas sensing, atmosphere analysis) and low cost thanks to the integration on planar substrate. In this context, we have developed singlemode optical waveguides in the mid-infrared based on Silicon/Germanium alloy integrated on silicon. These waveguides, compatible with standard microelectronic technologies present very low loss in the 3300 – 1300 cm^-1 range. This paper presents the design, technological realization, and characterization of array waveguide grating devices specifically developed for the simultaneous detection of several gas using arrays of QCL sources. Gas sensing generally requires a tunable source continuously covering the whole operational range of the QCL stack. With this objective, specific design has been adopted to flatten the optical transfer function of the whole multiplexers. Samples devices around 2235cm^-1 were realized and tested and showed results in good agreement with the modeling, flat transmission over a full 100 cm^-1 operational range were obtained with a peak-to-valley modulation of -5dB were experimentally measured. These devices will be soon associated with QCL arrays in order to provide integrated, powerful, multi wavelength, laser sources in the 2235 cm^-1 region applicable to NO, CO, and CO² multi-gas sensor.

The diversity of integrated photonic sensors such as LIDARs increased in part thanks to integrated laser sources development. Glass integrated lasers fit well sensing demand because of their high durability and great integration potential. We propose here a new kind of saturable absorber (SA) for glass integrated Q-switched lasers, based on a solgel matrix. This is intended to improve durability and output power of existing lasers, whose SA is often based on plastic materials.

While sol-gel is already used for optical limiting devices, its use as a host for SA has not been investigated so far. Due to its interesting properties such as durability, high laser induced damage threshold (LIDT) and coating convenience, it should also be a good candidate to realize a reliable SA matrix.

We mixed a hybrid organic-inorganic sol with toluene and (bis(4_dimethylaminodithiobenzil) nickel – BDN I, a SA dye molecule. Drops of this mix have been coated and annealed to obtain a SA sol-gel thick layer. We modeled BDN I with a four energy-level system and measured its absorption over optical input power at the wavelength of 1064nm in order to extract its physical parameters: absorption cross sections and relaxation time. This SA showed good performances with 30% modulation depth.

This sol-gel has also been spin coated on ion-exchanged glass integrated waveguide. The characteristics of this waveguide SA have been measured and the evanescent light interaction between the waveguide and the saturable absorber layer has been modeled. This study will allow further integrated Q-switched lasers design.

The integration of electrical and optical components on a single chip, favourable silicon, is a major goal in research. Thereby, a bottleneck is the integration of active and passive optical elements. Graphene, with its electrically tuneable absorption and ultrafast photoresponse, is a promising candidate to move a step closer towards high-speed on-chip integration. We fabricated a dual-gate tuneable pn-junction graphene phototdetector to investigate the relevant conversion mechanisms. The photodector is integrated on a silicon slot waveguide, which has twofold function. First, the two silicon strips of the slot waveguide are utilized as dual gate electrodes to create an electrically controllable pn-junction in the graphene. Second, the slot waveguide design allows confinement of light in subwavelength dimension. The confined light is directly absorbed in the slot between the n- and p-doped regions. At zero bias the conversion is dominated by the photo-thermoelectric effect, where we achieved a responsivity of 35 mA/W. While by applying a low bias of 300 mV, the responsivity increased to 76 mA/W due to an additional photoconductive contribution. The photoresponse of photodetectors based on the photo-thermoelectric effect arises from hot electrons, rather than lattice heating. Therefore, we could demonstrate that our graphene integrated photodetector based on a tuneable pn-junction reaches a setup-limited 3dB-bandwidth of 65 GHz, which is the highest value reported for a graphene-based phototedetector.

We propose a liquid polymeric compound based on photo-responsive azo-polymers to be used as light-activated optical element with tunable and reversible functionalities. The interaction of a laser beam locally modifies the liquid density thus producing a refractive index gradient. The laser induced refractive index profiles are observed along the optical axis of the microscope to evaluate the total phase shift induced and along the orthogonal direction to provide the axial distribution of the refractive index variation. The focusing and imaging properties of the liquid lenses as functions of the light intensity are illustrated.

Plasmonic nanocavities can control light flows and enhance light-mater interactions at subwavelength scale, and thus can potentially be used as nanoscale components in integrated optics systems either for passive optical coupling, or for active optical modulation and emission. In this work, we investigated a new type of multilayered metal-insulator optical nanocavities that can support multiple localized plasmon resonances with ultra-small mode volumes. The total number of resonance peaks and their resonance wavelengths can be freely and accurately controlled by simple geometric design rules. Multi-resonance plasmonic nanocavities can serve as a nanoscale wavelength-multiplexed optical components in integrated optics systems, such as optical couplers, light emitters, nanolasers, optical sensors, and optical modulators.

Over the past few decades, photonic technologies have emerged as a promising technology for data communications. They offer advantages such as high data bandwidths at comparable or even lower power consumption than electronics. However, photonic integrated circuits suffer from the diffraction limit of light which is a major obstacle in achieving small device footprints and densely packed on-chip interconnects. In recent years, plasmonics has emerged as a possible solution for densely packed on-chip nanophotonic circuitry. The field of plasmonics deals with oscillations of free electrons in a metal coupled to an electromagnetic field. The large wave-vector associated with these oscillations enables light to be localized in volumes much smaller than the diffraction limit. Consequently, there have been many demonstrations of plasmonic interconnects for on-chip communications, using well known metals such as gold and silver. However these materials are not CMOS compatible and hence their use is not technologically feasible. The growing need for plasmonic materials which are robust, cost-effective, and CMOS-compatible has led to the study of alternate plasmonic materials. For the visible and near infrared ranges, transition metal nitrides have been shown to be suitable metals for plasmonic applications These materials have optical properties comparable to that of gold and are CMOS-compatible, hence, they can be easily integrated into a silicon platform for on-chip applications. In this work, we demonstrate titanium nitride based plasmonic interconnects in an all-solid state geometry which can be easily integrated on a silicon platform.

Slot-based plasmonic waveguides have attracted significant attention owing to their unique ability to confine light within nanometer-scale. In this context, enhanced localized light-matter interaction and control have been exploited to demonstrate novel concepts in data communication and sensing applications revealing the immense potential of plasmonic slot waveguides. However, inherent light absorption in the metallic parts included is such structures hampers the scaling of plasmonic devices and limits their application diversity. A promising solution of such issues is the use of hybrid plasmo-photonic configurations. Hybrid slot waveguides have been introduced as the means to reduce such propagation losses while maintaining their functional advantages. In addition, their co-integration with low-loss photonic waveguides can enable the development of more complex structures with acceptable overall losses. In such scenario, light needs to be efficiently transferred from the photonic to the plasmonic components and/or backwards. Based on this rationale, in this work a hybrid slot-based structure is adopted to achieve highly efficient light transfer between photonic and plasmonic slot waveguides in the near-infrared spectrum region (λ=1550 nm). This transition is realized with the aid of a directional coupling scheme. For this purpose, a Si₃N₄ bus waveguide (photonic branch) is located below an Aubased metallic slot (plasmonic branch) forming a hybrid waveguide element. The combined configuration, as it is shown with the aid of numerical simulations , is capable of supporting two hybrid guided modes with quasi-even and odd symmetry allowing the development of a power exchange mechanism between the two branches. In this context, a new directional coupling structure has been designed which can achieve power transmission per transition over 68% within a coupling length of the order of just several microns.

Plasmonic technology has emerged as the most promising candidate to revolutionize future photonic-integrated-circuits (PICs) and deliver performance breakthroughs in diverse application areas by providing increased light-matter interaction at the nanometer scale, overcoming the diffraction limit. However, high insertion losses of plasmonic devices impede their practical deployment in PICs. To overcome this hurdle, selective integration of individual plasmonic devices on low-loss photonic platforms is considered, allowing for enhanced chip-scale functionalities with realistic power budgets. In this context, highly-efficient and fabrication-tolerant optical interfaces for co-planar plasmonic and photonic waveguides become essential, bridging these two “worlds” and ease combined high-volume manufacturing. Herein, a TM-mode butt-coupled interface for stoichiometric Si₃N₄ and Au-based thin-film plasmonic waveguides is proposed aiming to be utilized for bio-sensing applications. Following a systematic design process, this new configuration has been analyzed through 3D FDTD numerical simulations demonstrating coupling efficiencies up to 64% at the wavelength of 1.55 μm, with increased fabrication tolerance compared to silicon based waveguide alternatives.

In this work, we propose a magnetoplasmonic modulator for nonlinear radio-frequency (RF) modulation of an integrated optical signal. The modulator consists of a plasmonic Mach-Zehnder interferometer (MZI), constructed of the ferrimagnetic garnet, bismuth-substituted yttrium iron garnet (Bi:YIG). The transverse component of the Bi:YIG magnetization induces a nonreciprocal phase shift (NRPS) onto the guided optical mode, which can be actively modulated through external magnetic fields. In an MZI, the modulated phase shift in turn modulates the output optical intensity. Due to the highly nonlinear evolution of the Bi:YIG magnetization, we show that the spectrum of the output modulated intensity signal can contain harmonics of the driving RF field, frequency splitting around the driving frequency, down-conversion, or mixing of multiple RF signals. This device provides a unique mechanism of simultaneously generating a number of modulation frequencies within a single device.

Graphene, as the first identified two dimensional material, has shown great electro-optic response via Pauli-blocking for near IR frequencies and modulating functionality. However, this ability to modulate light is fundamentally challenged by its small optical cross-section leading to miniscule modal confinement factors in diffraction-limited photonics despite intrinsically high electro-optic absorption modulation (EAM) potential given by its strong index change. Yet the inherent polarization anisotropy in graphene and device tradeoffs lead to additional requirements with respect to electric field directions and modal confinement. The extinction ratio of graphene based EAM has, so far, been limited due to the small light matter interaction given the monolayer structure nature. Here we report an ultra-compact graphene based EAM by integrating graphene with a plasmonic slot waveguide. We show that the modal confinement and hence the modulation strength of a single-layer modulated graphene in this plasmonically confined mode is able to improve by more than 10x compared to diffraction-limited modes. Combined with the strong-index modulation of graphene the modulation strength could achieve more than 1dB/um, which is more than 2-orders of magnitude higher compared to Silicon platform graphene modulators. Furthermore, the modal confinement was found to be synergistic with performance optimization via enhanced light-matter-interactions. These results show that there is room for scaling 2D material EAMs with respect to modal engineering towards realizing synergistic designs leading to high-performance modulators.

Metal-semiconductor-metal (MSM) photodiodes are commonly used in ultrafast photoelectronic devices. Recently it was shown that localized surface plasmons can sufficiently enhance photodetector capabilities at both infrared and visible wavelengths. Such structures are of great interest since they can be used for fast, broadband detection. By utilizing the properties of plasmonic structures it is possible to design photodetectors that are sensitive to the polarization state of the incident wave. The direct electrical readout of the polarization state of an incident optical beam has many important applications, especially in telecommunications, bio-imaging and photonic computing. Furthermore, the fact that surface plasmon polaritons can circumvent the diffraction limit, opens up significant opportunities to use them to guide signals between logic gates in modern integrated circuits where small dimensions are highly desirable. Here we demonstrate two MSM photodetectors integrated with aluminum nanoantennas capable of distinguishing orthogonal states of either linearly or circularly polarized light with no additional filters. The localized plasmon resonances of the antennas lead to selective screening of the underlying silicon from light with a particular polarization state. The non-null response of the devices to each of the basis states expands the potential utility of the photodetectors while improving precision. We also demonstrate a design of waveguide-coupled MSM photodetector suitable for planar detection of surface plasmons.

In this paper, a surface plasmon resonance sensor for the detection of refractive index variation is presented. A novel waveguide type surface plasmon resonance sensing configuration with focal length variable liquid lens is introduced. The method of surface plasmon resonance sensor is based on the waveguide type with incident angle variation. The incident angle is varied by using an electrowetting liquid lens which is possible to actively change focal length as applying voltage. The optical system, which is adapted to electrowetting lens can continuously change the incident angle of light from 73 to 78 degrees with compact size. The surface plasmon waves are excited between metal and dielectric interface. The sensing surfaces are prepared by a coating of gold metal above high refractive index glass substrate. The incident light which is 532nm monochromatic light source passes through a noble metal coated substrate to detect intensity with incident angle variation. An analysis to distinguish the contribution of light with various incident angle is focused on the angular characteristics of the surface plasmon sensor under wavelength interrogation. The resonance angle is determined corresponding to sensing material refractive index with high sensitivity. The result suggests that the performance of surface plasmon resonance sensor can be improved by real time varying incident angle. From this presented study, it provides a different approach for angular interrogation surface plasmon resonance sensor and can be miniaturized for a portable device.

In this invited contribution I will review recent results of our research in the field of complex nanolasers. I will begin by discussing recent experimental results from a new type of ultra-dark nanoparticles, which behave as an ideal black-body and spontaneously produce single color pulses thanks to an equivalent Bose-Einstein Condensation of light.¹ I will then discuss new quantum information sources from core-shell spaser nanoparticles.² Finally, I will illustrate a new type of laser source that emits only in the near field, discussing applications in integrated optical circuits.

The investigation of multi-photon quantum interference in symmetric multi-port splitters has both fundamental and applicative interest. Destructive quantum interference in devices with specific symmetry leads to the suppression of a large number of possible output states, generalizing the Hong-Ou-Mandel effect; simple suppression laws have been developed for interferometers implementing the Fourier or the Hadamard transform over the modes. In fact, these enhanced interference features in the output distribution can be used to assess the indistinguishability of single-photon sources, and symmetric interferometers have been envisaged as benchmark or validation devices for Boson-Sampling machines. In this work we devise an innovative approach to implement symmetric multi-mode interferometers that realize the Fourier and Hadamard transform over the optical modes, exploiting integrated waveguide circuits. Our design is based on the optical implementations of the Fast-Fourier and Fast-Hadamard transform algorithms, and exploits a novel three-dimensional layout which is made possible by the unique capabilities of femtosecond laser waveguide writing. We fabricate devices with m = 4 and m = 8 modes and we let two identical photons evolve in the circuit. By characterizing the coincidence output distribution we are able to observe experimentally the known suppression laws for the output states. In particular, we characterize the robustness of this approach to assess the photons' indistinguishability and to rule out alternative non-quantum states of light. The reported results pave the way to the adoption of symmetric multiport interferometers as pivotal tools in the diagnostics and certification of quantum photonic platforms.

We present the laboratory characterisation of the first working, mid-infrared, integrated optics, 4-channel interferometric beam combiner based on the properties of two-dimensional arrays of evanescently coupled waveguides. Potential applications of the component to astronomy, biology and quantum optics are proposed and discussed.

Electronic interconnects are reaching their limit in terms of speed, dimensions and permissible power consumption. This has been a major concern in data centers and large scale computing platforms, creating limits to their scalability especially with respect to power consumption. Silicon photonic-electronic integration is viewed as a viable alternative that enables reliability, high efficiency, low cost and small footprint. In particular, silicon with its high refractive index, has enabled the integration a many individual optical elements (ring resonators) in small areas. Though silicon has a high thermo-optic coefficient (1.8×10^-4/°C) compared to silica, small thermal fluctuations can affect the optical performance especially for WDM applications. Therefore, a passive athermal solution for silicon photonic devices is required in order to reduce thermal sensitivity and power consumption. We have achieved this goal by replacing the silica top cladding with negative thermo-optic coefficient (TOC) materials. While polymers and titanium dioxide(titania) have a negative TOC, polymers can’t handle high temperature processing and titania needs very tight thickness control and expensive deposition under vacuum. In this work we propose to use a sol-gel inorganic-organic hybrid material that has the benefits of both worlds. We were able to find optimum curing conditions to athermalize ring resonators by studying various sol-gel curing times and curing temperatures. Our athermal rings operate in a wide temperature range from 5C – 100C with thermal shifts below 1pm/C and low loss. Furthermore, we demonstrate that our athermal approach does not deleteriously effect critical device parameters, such as insertion loss and resonator Q factors.

We propose a novel waveguide type based on the concept of strip-loaded waveguide. A strip-loaded waveguide is composed of a thin-film slab waveguide allowing a vertical confinement of the electromagnetic field. A lower refractive index strip provides the lateral confinement by inducing a slight modification of the effective index in the slab. By using such a generic device we will demonstrate how the limits of integrated photonics can be extended, especially, in terms of propagation losses while adding complex structure on the waveguide. Since light sees only a slight variation of effective index, and not an abrupt change of material, propagation losses of the device are fully determined by the film rather than by the structuration. Different micro- and nano-structures will be presented through simulation and experimental results. We will focus especially on the study of Y-junctions, ring resonators, interferometers, and Bragg gratings. Another advantage of strip-loaded waveguides is the simplicity of fabrication. In order to fabricate the devices we employed nano-imprinting of polymer, a fabrication technique suitable for mass production. The low refractive index of the polymer allows a large panel of materials for the slab waveguide, e.g., silicon, titanium dioxide, and lithium niobate. This diversity in the choice of the materials gives to the platform the potential to operate on a wide wavelength range from UV to IR, for multiple applications in telecommunications, sensing and bio-sensing, and medical devices.

We study the Bloch surface wave based nano-thin 2D optical components. The 2D elements are fabricated on the dielectric multilayer platform which sustains the Bloch surface waves. Such a platform is considered as a novel foundation for planar integrated optics. We exploit the total internal reflection configuration to achieve the phase matching condition for BSW excitation. Because of the evanescent behavior of the BSW, we use a scanning near field optical microscope to characterize the near-field properties of in-plane components. The 2D optical components include Disk resonators and Bessel-like beams.

Microscale resonators that simultaneously exhibit high-Q optical and mechanical resonances are routinely used to study the coupling between light and vibration. We have learned recently that Brillouin scattering (traveling-wave light-sound interactions) within simple dielectric whispering-gallery resonators can enable nonreciprocal optical transmission through a waveguide, which can be reconfigured optically and on demand. In this talk, we describe the basic theory and experimental demonstrations of Brillouin Optomechanics, and describe how it allows the breaking of time-reversal symmetry by means of traveling phonon modes. We experimentally demonstrate ultra-low loss optical isolation using a simple resonator system. Our results demonstrate that chip-scale optical isolation is much more accessible than previously thought. (invited by Prof. Xudong Fan)

An optical 3-bit Excess-3 code converter is demonstrated by using Mach-Zehnder Interferometers based on electro-optic effect. It is a way to represent values with a balanced number of positive and negative numbers using a prespecified number N as a biasing value.

The transmission properties of side-coupled circular cavity systems are studied based on numerical two-dimensional finite-difference time domain modeling. The spatial asymmetry is introduced due to different separations between the circular resonators and side-coupled stripe waveguides. These structures can be viewed as 4-port routers where different ports are connected due resonant coupling between the guided modes in stripe-waveguides and whispering gallery modes in circle resonators. It is found that due to strongly asymmetric geometry, significant optical losses, and mode conversion processes, such structures display strongly asymmetric optical transmission properties for the waves propagating in forward and backward directions between the ports. In non-optimized single microcavity structures, it results in isolation ratios on the order of 10 dB for wavelengths resonant with WGMs. In structures formed by two closely spaced circular resonators, WGMs are strongly coupled leading to formation of bonding and antibonding photonic molecular modes. It is shown that at the wavelengths resonant with hybridized molecular modes the isolation ratios can be increased beyond 20 dB. At the same time, different wavelengths can be preferentially coupled to different ports resulting in wavelength demultiplexing functionality.

Copper-doped planar glass waveguides were prepared by thermal ion exchange technique in molten mixture of copper sulfate and sodium sulfate (molar ratio of 50:50%) at temperatures of 565-605°C and different diffusion times of 15-30 minutes. The effective indices were measured by means of prism-coupled technique, and the refractive index profiles of the waveguides were reconstructed by IWKB method. The photoluminescence (PL) of the waveguides were studied at room temperature. The broad blue-green emission bands centered 510 nm (at the excitation wavelength of 286 nm) were observed on the waveguides. The refractive index profiles and the blue-green luminescence of the waveguides were strongly influenced by the prepared and annealed processes.

We present the design of 20-channel, 50-GHz Si₃N₄ based AWG applying our proprietary AWG-Parameters tool. For the simulations of the AWG layout we used PHASAR photonics tool from Optiwave. The simulated transmission characteristics were then evaluated applying our AWG-Analyzer tool. We studied the influence of one of the design parameters – the separation between input/output waveguides, dx on the channel crosstalk. The results show that there is some minimum waveguide separation necessary to keep the crosstalk between transmitting channels low. The AWGs were designed for TM-polarized light with a central wavelength of 850 nm. They will later be used in a photonic integrated circuit dedicated to medical diagnostic imaging applications.

The most common application of optical Y-splitters is their use in FTTx networks. It allows several customers to share the same physical medium, bringing high-speed networking, digital television and telephone services to residences using fiber-optic cables. The task of the optical splitters in such FTTH networks is to split one optical signal in many identical signals bringing for example the same TV signal in different households. Of course, the more buildings can be served by one optical splitter the lower are the installation costs. Therefore, the special attention is paid mainly to the design of high channel optical splitters presenting the serious challenge for the professional designers. In this paper a new Y-branch shape is proposed for 1×32 Y-branch splitter ensuring better splitting properties compared to the one recommended by ITU, in terms of their performance in transmission systems using wavelength division multiplexing.

In this contribution, we give a comprehensive overview of the fabrication, characterization, and application of integrated planar waveguide Bragg gratings (PPBGs) in cyclo-olefin copolymers (COC). Starting with the measurement of the refractive index depth profile of integrated UV-written structures in COC by phase shifting Mach-Zehnder- Interferometry, we analyze the light propagation using numerical simulations. Furthermore, we show the rapid fabrication of humidity insensitive polymer waveguide Bragg gratings in cyclo-olefin copolymers and discuss the influence of the UV-dosage onto the spectral characteristics and the transmission behavior of the waveguide. Based on these measurements we exemplify that our Bragg gratings exhibit a reflectivity of over 99 % and are highly suitable for sensing applications. With regard to a negligible affinity to absorb water and in conjunction with high temperature stability these polymer devices are ideal for mechanical deformation sensing. Since planar structures are not limited to tensile but can also be applied for measuring compressive strain, we manufacture different functional devices and corroborate their applicability as optical sensors. Exemplarily, we highlight a temperature referenced PPBG sensor written into a femtosecond-laser cut tensile test geometry for tensile and compressive strain sensing. Furthermore, a flexible polymer planar shape sensor is presented.