Chair introduction to the SPIE Photonics West 2022 conference on Quantum Sensing and Nano Electronics and Photonics XVIII.

Nanophotonics can play important roles for next generation electromagnetic measurements and communications. At present, critical Electromagnetic (EM) properties such as radar cross section (RCS) and inverse synthetic aperture radar image (ISAR) are often measured in anechoic chambers. But for very large structures, this could be expensive or impractical due to the sheer size of the structure. Maxwell's equations are invariant under dilatation transformation. It is possible to make the measurement on reduced size models and using proportionally higher frequencies. By conserving the scale factor between model and wavelength, the solution is identical. Thus, using nanophotonics, we create a 3D- printed emulator at the light wavelength for high resolution scaled RCS/ISAR measurements of large complex microwave and millimeter wave EM structures. The RCS and ISAR of the EM structure is consequently measured by an ultra-compact benchtop coherent optical measurement range. In addition, we develop quantum dot coupled active plasmonic nano antenna that can integrate with nano-photonic emulator to study RF antenna propagation inside complex electromagnetic structures.

Color centers in nanodiamonds are promising candidates to realize high-bandwidth quantum optical devices integrated on mature photonic platforms. However, both the optical properties of these emitters and the geometries of host nanoparticles are highly heterogenous. The interfacing of nanodiamond-based color centers with the on-chip photonic circuitry requires their careful pre-selection and deterministic manipulation with nanoscale precision. We present a suite of recently developed techniques for rapid emitter selection and nanofabrication aimed at realizing deterministically assembled plasmon-enhanced single-photon sources. These techniques include optical nanoparticle metrology, machine learning for quantum optical measurements, probe-assisted nanoantenna assembly and the control of plasmonic cavity volume through photomodification.

Nitrogen-vacancy (NV) centers in diamond have emerged as promising room temperature quantum sensors for probing condensed matter phenomena ranging from spin liquids, 2D magnetic materials, and magnons to hydrodynamic flow of current. Here, we propose and demonstrate that the NV center in diamond can be used as a quantum sensor for detecting the photonic spin density. We demonstrate this probe both for the case of a single NV center and an ensemble of NV centers. The spinning field of light induces an effective static magnetic field in the spin qubit probe. We perform room-temperature sensing using Bloch sphere operations driven by a microwave field (XY8 protocol) to detect the photonic spin density induced effective static magnetic field.

A Peltier cooled long wavelength infrared (LWIR ) position sensitive photon detector (PSD) based on the lateral effect is reported for the first time. It is a modified PIN LWIR HgCdTe photodiode forming the tetra lateral PSD of the photosensitive area 1×1 mm2, cooled to 205 K, optimized for the 4-11 µm wavelength band and reverse biased. The position resolution close to 1 µm was achieved with 32x averaging of 100 ns QCL laser pulses of the 10.5 µm wavelength and the 0.3 nJ energy focused on the spot of 240 µm 1/e2 diameter, with the box-car integration times of 1 µs and correlated double sampling.

A variety of mid-, long - and very long– wavelength infrared (MWIR, LWIR and VLWIR) detectors and focal plane arrays utilizing InAs/InAsSb superlattices have been demonstrated in the last decade. At the same time, the transport properties of minority carriers in these structures became an area of active investigation after initial observations of hole localization at low temperatures attributed to the nonuniformity of superlattice layers thickness. In this work we study the dependence of minority carrier (hole) transport, absorption coefficient and quantum efficiency (QE) of a 5.6 µm cut-off wavelength MWIR InAs/InAsSb detector on temperatures and applied bias

We present strong radio-frequency current modulation close to their repetition frequency as a means to control the emitted state of quantum cascade laser frequency combs. In particular, more than doubling of the spectral bandwidth compared to free-running can be achieved throughout the dynamical range of the device. By changing the modulation frequency, the spectral bandwidth and center-frequency can be tuned and by fast switching between modulation frequencies we can multiplex spectral regions with negligible overlap from the same device. In the time-domain, we are able to transition from quasi-continuous to long-pulse output by injecting at high power.

A terahertz intersubband emitter based on silicon is presented. The emission originates from n-type Ge/SiGe quantum cascade structures. We designed a strain-compensated single quantum active region based on a vertical optical transition and tensile-strained Si0.15Ge0.85 barriers. The 51 quantum cascade periods (corresponding to 4.2 μm) were grown on a Si1-xGex reverse graded virtual substrate on Ge/Si(001) substrates. Deeply etched diffraction gratings were processed and the surface emitting devices were characterized at 5 K with a Fourier transform infrared spectrometer. We observed two distinct peaks at 3.4 and 4.9 THz with a line broadening of 20%. This is an important step towards the realization of an Ge/SiGe THz quantum cascade laser.

We present a planarized double metal waveguide THz quantum cascade laser, where the top contact metallization extends beyond the active region, above the surrounding low-loss BCB polymer. Placing wire bonds over the BCB-covered area enables the fabrication of extremely narrow waveguide dimensions with reduced power dissipation. Compared to a standard double metal waveguide, improvements in waveguide losses, dispersion, RF and thermal properties are observed. Measurement results feature frequency comb operation with free-running beatnotes as strong as -30 dBm, self-starting harmonic states, RF-driven broadband emission, comb operation up to 110 K, and laser operation up to 118 K in continuous-wave.

THz QCLs are promising sources towards achieving octave-spanning comb operation and self-referencing in a monolithic device. We investigate the spectral mode phase relations by means of SWIFT of free running and strongly RF modulated devices. The inspected QCLs are based on an octave-spanning, heterogeneous and a 1.8 THz spanning, homogeneous active region design. The extracted neighboring mode phase differences from SWIFT of free running devices show the FM nature of the comb emission. When strongly RF modulated the spectrum is broadened and both AM and FM states are be observed.

This work theoretically demonstrates that the ultimate detectivities in interband cascade infrared photodetectors (ICIPs) with identical discrete absorbers are the same as that in a single-absorber detector in the limit of perfect collection, but higher than that in the single-stage detector with a finite diffusion length. Detailed derivations and calculations, along with relevant discussion, are provided to show how ICIPs are optimized for maximizing the detectivity and to understand their underlying physics. ICIPs with identical discrete absorbers are of more significance for practical applications such as those that require high-speed response or circumventing the diffusion length limitation.

An “ultra-wide” stripe Fabry-Perot cavity is designed with losses distributed to selectively scatter high order modes. We show that optimizing ultra-wide QCL devices for quasi-continuous wave operation can enable a high brightness continuous wave beam that is multiplexed and then polarization beam combined. We also expand on the use of angled cavity waveguides that are overlapped as a means to provide multiple coherent emitters on a laser bar. We introduce the strategically etched notches in angled cavity architectures to provide a large area for gain while reinforcing fundamental mode-like behavior.

THz imaging often struggles to achieve necessary framerates for applications, but recent demonstrations show that an imaging system based upon THz-to-optical conversion in atomic vapour can provide ultrahigh speeds while retaining sensitivity with optical cameras. This atomic vapour imaging requires a multi-frequency near-IR optical pumping system, and we demonstrate a compact system to provide the stable frequencies required for conversion of 0.55 THz light to visible (green) in caesium atoms. Through the integration of distributed feedback (DFB) laser diodes and a compact extended cavity diode laser, and spectroscopy and offset locks based on open-source FPGA and Arduino code, it approaches suitability for wider industrial application.

Quartz-enhanced photoacoustic spectroscopy (QEPAS) is one of the most efficient ways to obtain sensitive, selective, robust gas sensors, where the signal can be given with a fast response and measured continuously. The main drawback of QEPAS comes from using a quartz tuning fork (QTF) as a mechanical transducer. QTF is not designed for photoacoustic gas sensing, and its further integration is limited. We propose a silicon resonant MEMS based on a capacitive transduction mechanism with a limit of detection comparable to that of a QTF. This sensor is potentially an efficient sound wave transducer that can advantageously replace a QTF

Spin optoelectronics aims at interconverting photon spins to charges and has the potential to revolutionize telecommunications. Circularly-polarized light emitters rely on spin lasers whereas reciprocal devices consist of solid-state helicity detectors, the fabrication of which has remained a challenge for decades. Experimental results obtained on a spin photodiode based on a ferromagnetic-metal/GaAs tunnel junction will be presented and we will show that the helicity-dependent photocurrent is mostly determined by a dynamical factor resulting from the competition between carrier recombination in the metal and in the semiconductor. This constitutes a radical shift in the physical description of these emerging spin devices.

Miniaturisation of laser sources is crucial to the translation of quantum technologies from the laboratory to the real world. Typically, the lasers required for cooling and trapping of atoms and ions make up a significant footprint of the measurement system. Increasing robustness and reliability whilst removing noise sources is a key challenge whilst reducing volume. Direct generation GaN based external cavity diode lasers offer lower SWaP-C compared to traditional frequency doubled alternatives. Butterfly packaged single frequency sources operation in the blue - UV allow numerous atomic transitions including Sr, Sr+, Yt, Yb+, Mg and Ca to be targeted.

Photonic quantum technologies require single photon sources and detectors operating at high efficiency, but at high rates detector imperfections can lead to inaccurate measurements. We show that the combination of the detector deadtime and the source statistics together determine the saturation level of a single photon detector, with anti-bunched sources leading to a greater detection rate than coherent or thermal light of the same intensity. At high photon rates this behavior distorts second-, third- and fourth- order correlation measurements, in agreement with our numerical simulations. Finally, we discuss the implications for entangled light detection and photonic logic.

We theoretically reveal novel quantum effects in the interaction between free electrons and optically illuminated multilevel atomic systems. Specifically, we show that the resulting electron energy-loss spectra are radically altered in the presence of intense laser irradiation, giving rise to transition energy shifts and new loss features associated with the combined action of photon and electron exchanges with the atomic system, in analogy to Raman scattering. Besides their fundamental interest, our results provide the basis for a new form of spectrally resolved microscopy in which the external illumination is used to enhance the spectral resolution and strength of electron-atom interactions.

Integrated photonic circuits hold the promise of cost-effective and compact elements to generate and detect beams of a specific topological mode order of orbital-angular-momentum (OAM). This keynote will describe various metasurface structures that can be used for generating and detecting such OAM beams. The presentation will emphasize key beneficial characteristics for system operation, including the ability to dynamically tune the mode order and to perform functions over a broad spectral band.

Multiphoton lithography is a laser-based additive manufacturing technique which allows the free-form fabrication of 3D structures with sub-100nm resolution. In this talk, I present our latest work into the 3D printing of high resolution structures for applications in photonics, micro-optics and biomedicine.

Infrared spatial modulation spectroscopy enables one to acquire background-free spectra of subwavelength sized objects. With this method we have investigated thermally excited single and double metal-insulator-metal plasmonic antennas (MIMs). On single MIMs with silica insulator, the same resonance condition is satisfied at different wavelengths due to the strong dispersion of silica. On double MIMs, the thermal radiation spectra bear the signature of hybridized electromagnetic modes which are simultaneously excited when the gap separation between the antennas is in the 100 nm range.

Metaphotonic structures with their unconventional optical properties due to their subwavelength feature sizes, are of great interest for applications that require engineering and manipulation of an optical wavefront. A long-lasting challenge in this field has been the formation of dynamically reconfigurable metaphotonic structures. This talk is focused on creation of such reconfigurable structures using hybrid material platforms that integrate plasmonic/dielectric and phase-change materials. Design approaches as well as fabrication processes and characterization results for novel dynamically reconfigurable metasurfaces with electrical reconfiguration will be presented. The fundamental properties of such devices and their use for enabling novel state-of-the-art applications including dynamic wavefront engineering, ranging, display, and signal processing will also be discussed.

Bound states in the continuum (BICs) can be observed in photonic crystal slabs embedded in low refractive index surroundings that makes challenging their realization. Here we propose a configuration implemented on a high refractive index bulk substrate with a one-dimensional grating positioned on a distributed Bragg reflector (DBR). Judiciously designed DBR reflects all diffraction orders induced by the grating entirely eliminating radiative losses. The configuration enables a high degree of design freedom facilitating the realization of very high quality factor cavities in conventional all-semiconductor technology.

The modification of images to enhance and manipulate images is ubiquitous in contemporary image processing. Digital methods, however, require energy and challenges arise with the increasing amount of data being processed. Furthermore, cameras cannot directly sense phase variations in an optical field and, although computational methods have been developed to extract phase information from intensity, these are also relatively slow and data intensive. All-optical approaches to real-time image processing, on the other hand, are well-established but require the use of comparatively bulky optical components incompatible with the current push to device miniaturization. Here, the use of ultra-compact nanoscale resonant waveguide gratings and meta-optics for manipulating amplitude and phase objects will be presented.

Solar photoelectrochemical water splitting is a potential pathway for large-scale renewable fuel generation with minimum carbon footprint. It utilizes semiconductors to absorb photons and generate charge carriers for redox processes leading to hydrogen and oxygen evolution. A major challenge is the scarcity of materials satisfying all the criteria associated with efficiency, cost, scalability and stability. A few of the recently emerged 0 and 2D semiconductors have demonstrated remarkable ability to form heterostructures with unique properties for addressing these issues. In this presentation, these structures exhibiting quantum size effects and the advancements in the field are discussed.

The World Health Organization has defined cardiovascular diseases as the number one cause of death in the world [1]. The diagnosis of these diseases can be invasive for the patient. With the introduction of new technologies in the medical field, scientists and doctors are working together to find new and less invasive ways to ease medical procedures. For many years, scientists have shed light on several gases present in the exhaled breath: water vapor, nitrogen, oxygen, carbon monoxide (CO)... Some of them are biomarkers and their investigation can lead to the diagnosis of several diseases. We present a Quartz enhanced photoacoustic (QEPAS) [2] sensor based on infrared lasers, dedicated to CO, nitric oxide (NO), and acetone monitoring. CO sensing is performed with a 4.7 um quantum cascade laser. This sensor has proved its sensibility and selectivity with a limit of detection of 20 ppbv in 1s. Therefore, further measurements were also performed in situ in the hospital to confront the sensor to a medical sensor. We have demonstrated the influence of the breath hold, characterized different respiratory compartments and discriminated smokers and non-smokers volunteers [3]. These first measures made on humans have brought out some physiological points that need to be taken in account. The QEPAS signal depends on the resonance frequency (f0) of the quartz tuning fork (QTF). The humidity naturally present in breath causes a shift of f0. Some improvements have been proposed to track f0 and the QTF Q-factor to stabilize the measurement [4].

Most photodetectors offered by VIGO are made of mercury-cadmium telluride compound (MCT) by Metalorganic Chemical Vapour Deposition (MOCVD) technology. Despite many advantages of MCT compound, including lattice parameter being almost independent on composition, nowadays in some applications, detectors containing mercury, cadmium and lead are successively removed from the consumer market through norms and directives (e.g. RoHS) due to their toxicity. The abovementioned limitations connected to MCT encouraged the company to find alternative material system and technology as a replacement. Inspired by literature, VIGO decided to develop Ga-free InAs/InAsSb superlattices which are a great candidate, operating in a similar wavelength regime from MWIR to VLWIR. We continue our idea of backside-illuminated devices using substrate material (GaAs) as an immersion lens. We still take advantage of detector material lattice-matched to the buffer layer, replacing CdTe and HgCdTe by GaSb and InAs/InAsSb SL, respectively. The architecture of SLs-based heterostructures originates from MCT photovoltaic devices and utilizes wide bandgap depletion layers for dark current reduction. The detectivity of SL devices is similar to MCT (Fig. 1). Currently, VIGO efforts are focused on the development of HOT LWIR photodiodes including thin absorber devices.

MBE and MOVPE growths of InP-based extended wavelength and GaSb-based IR emitter and detector structures have progressed to production mode. These photonics device structures are typically grown using large format, multi wafer MBE and MOCVD tools and on large diameter substrates (100 to 150 mm). In this work, material characterization data of advanced InP- and GaSb based epitaxial structures will be shown. Multi point measurements showing cross-wafer and cross-platen uniformity will also be shared. Finally, detailed analysis of run-to-run epiwafer data will be presented to demonstrate the manufacturability of our production epitaxial process for these advanced photonics device structures.