This PDF file contains the front matter associated with SPIE Proceedings Volume 11690, including the Title Page, Copyright Information, and Table of Contents.

We have been investigating an optical phased array (OPA) using an electro-optic (EO) polymer, that can control the shape and direction of an optical beam at high speed. In this study, we propose an OPA which consists of hybrid waveguides with organic and inorganic optical core materials. By applying the taper structure to the inorganic core at the connection part, we inproved coupling efficiency.

Inevitable manufacturing tolerances strongly degrade the fabrication yield of photonic integrated circuits (PICs), unless their effect on overall PIC performance characteristics is considered and mitigated during the PIC design process. This is especially true for PICs containing interferometric sub-circuits such as micro-ring optical filters, Mach-Zehnder interferometers, and arrayed waveguide gratings. The problem rapidly increases with the growth of complexity, which is currently observed while designing PICs for large-scale optical interconnects, LIDAR distribution networks, all-optical activation units for artificial neural networks, and multi-ring filters with complex custom transfer functions. Maximizing fabrication yield in such cases is a highly non-trivial task – it requires the development of special design approaches and easy access to statistical performance techniques during the simulations. We present a general-purpose schematic-driven PIC design framework that provides easy access to statistical performance techniques. Our design framework is based on statistical compact simulation models (CSMs) representing the photonic and optoelectronic building blocks (BBs) of foundry-specific process design kits (PDKs). We introduce a special technique that allows identifying critical light paths and applying automated phase compensation inside the models, which significantly simplifies the tolerances analysis, including estimating the final fabrication yield. The analysis of statistical parameter variations due to manufacturing tolerances on-waver and between wavers is supported as well by our presented approach. We demonstrate its application on complex PIC designs comprising of passive and active photonic building blocks.

Silicon nitride (SiNx), an associated CMOS photonics enabling material, provides a promising and complementary photonic platform for the development of low-cost CMOS compatible waveguides and related photonic components. We propose a 16 element - 2D scanning optical phased array circuit based on a Si-rich core, which reconciliates the requirements of power handling and field-of-view for automotive LiDAR. This dispersive optical phased array consists of wavelength-dependent grating coupler antenna arrays and spiral-delay lines that allow achieving a field-of-view of (35°x 17°) and an angular resolution of (0.15°x1.2°).

Over the last decade, Optical Phased Arrays (OPA) have been extensively studied, targeting applications such as Light Detection And Ranging (LiDAR) systems, holographic displays, atmospheric monitoring and free space communications. Leveraging the maturity of the silicon photonics platform, the usual mechanical based beam steering system could be replaced by an integrated OPA; significantly reducing the cost and size of the LiDAR while improving its performance (scanning speed, power efficiency, resolution…) thanks to solid state beam steering. However, the realization of an OPA that meets the specifications of a LiDAR system (low divergence and single output beam) is not trivial. Targeting the realization of a complete LiDAR system, the technical challenges inherent to the development of high performance OPAs have been studied at CEA LETI. In particular, efficient genetic algorithms have been developed for the calibration of high channel count OPAs as well as an advanced measurement setup compatible with wafer-scale OPA characterization.

We present an optical phased array parameter analysis for automotive and handheld device applications and preliminary results from a 1×16 silicon optical phased array using p-i-n phase shifters built on a 300-mm industrial platform to reach high-speed operation and low power consumption at a 1.55𝜇𝑚 wavelength. Using 2 𝜇𝑚-spaced grating antennas OPA with theoretical beam steering range of 48°, we demonstrate a beam steering range of ±4° while average power consumption after the beam-shape optimization is measured to be 12.6 mW. Experimental setup, beam forming and scanning are discussed and a final analysis on future large-scale OPA integration is made.

This paper presents the optimization of novel material stacks and functions targeting solid-state phase-front shaping in NIR for sensing (LiDAR, imaging, spectroscopy). We report on direct time-of-flight and frequency modulated continuous wave detection and ranging (LiDAR) implementing 2D scanners with on-chip optical calibration using Si-based photon-assisted tunneling diodes at 1.55µm. We finally introduce developments towards multi-beam scanning with low divergence, low power phase shifting and advanced light source integration through PIC hybridization with gain media, all key developments for LiDAR and alternative emerging applications, e.g. line-of-sight optical telecom, deep tissue imaging and gas sensing.

In the talk, we will present our recent work on mid-IR gas sensing using highly confined surface modes in graphene and hBN nanoresonators. We have used ultrathin functional coatings to selectively concentrate the target gas molecules in proximity of the 2D nanostructures, just like recognition elements are used in biosensors. As a proof of concept we have demonstrated CO2 sensing using graphene nanoribbons coated with a 10nm polyethylenimine chemisorber. We will discuss the different sensing mechanisms that can be leveraged (e.g. plasmon tuning via polymer-induced chemical doping) and the possibility to extend this platform to other 2D materials like hBN.

The development of a foundry-scale waveguide-enhanced Raman spectroscopy (WERS) platform is a vital for the widespead implementation of this analytical technique. In this work we analyze the waveguide material and fabrication processes offered by AIM Photonics with regard to their effectiveness for WERS, and other sensing techniques. Optical characterization of these materials via white light spectroscopy and fluorescence spectroscopy points to the designation of an optimal wafer composition comprising a thermal bottom oxide and an LPCVD silicon nitride waveguide. This optimal composition has no measurable fluorescence and a propagation loss of 3.2 dB/m at 1064 nm in the TM₀₀ mode. In the c/l band, the optimal wafer build has as thermal bottom oxide, a PECVD silicon nitride waveguide, and is annealed. This build has a propagation loss of 8.1 dB/m at 1550 nm in the TE₀₀ mode.

High-speed tracking of nano-objects is a gateway to understanding biological processes at the nanoscale. Here we will present our results on tracking single or ensembles of nano-objects inside optofluidic fibers via elastic light scattering. The nano-objects diffuse inside a channel of a microstructured fiber and the light scattered by the nano-object is detected transversely via a microscope. We will present the fundamentals of this approach and focus on selected results including retrieval of the full 3D trajectory of a diffusing nano-sphere, the simultaneous detection of hundreds of nano-objects in hollow core anti-resonant fibers and first results on inactivated SARS-CoV-2.

We report an ultrasensitive and selective plasmonic sensor for the detection of biomolecules, metal ions and small molecules. The sensor is comprised of low-power light-emitting diode, a multimode optical fiber coupler, a miniature spectrometer and multimode optical fibers with their facet coated with gold nanoparticles. It monitors the nanospectroscopic absorption changes of the plasmon resonance spectrum of the gold nanoparticles. The integration of these sensors for real time, on-line and multiplexing monitoring into microfluidics platforms is straightforward, and may be applied to many different fields, from environmental monitoring to cell biology studies.

This Conference Presentation, “Scalable fast-Fourier-transform-based (FFT-based) integrated optical neural network for compact and energy-efficient deep learning,” was recorded for the Photonics West 2021 Digital Forum.

A new compact optical circulator based on a photonic crystal made of a triangular lattice of air holes etched in a magneto-optical material that does not require an external DC magnetic field to keep its saturated magnetic state is presented. The design has a threefold rotational symmetry and it consists of three single-mode waveguides and one resonator supporting dipole resonances introduced in the photonic crystal structure. Computational simulations of the circulator demonstrate that, at the 1.55 µm wavelength, the insertion losses are about -1 dB, while the isolation and reflection levels are about -15 dB and -24 dB, respectively.

Roughness has always been a key detractor of the optical losses within the silicon photonics devices. With scaling at 300mm wafer, there is an introduction of new tools such immersion lithography scanner, OPC technique that can help to drive furthermore the optical losses reduction. This study will detail the work done on characterizing multiple steps of the process (Lithography, Etch, Annealing) and using roughness tools such LER (Line Edge Roughness), LWR (Line Width Roughness) and finally PSD (Power Spectral Density) to understand the main detractor of the optical losses at each step. These data will be extracted using SEM imaging from VeritySEM 6i.

Photonic integrated circuits (PICs) have been a powerful tool in advanced optical communication systems but now their application fields are expanding into those of sensing, imaging, and computing. Indium phosphide (InP), which is a traditional material for telecom PICs, is also good in other applications because it gives higher speed and functionality. Silicon PICs on the other hand gives us higher level of integration and manufacturability. Both approaches are to be utilized, depending on user’s requirements. In this talk, our photonic phased array integrated circuits on InP and silicon, as well as their applications to one pixel imaging, are reviewed. Then, as an example of PICs for computing, our optical unitary converter integrated circuits (OUCs) mainly on silicon toward all-optical multi-input multi-output (MIMO) processors are introduced.

Optical artificial neural networks (ONNs) have significant potential for ultra-high computing speed and energy efficiency. We report a novel approach to ONNs that uses integrated Kerr optical micro-combs. This approach is programmable and scalable and is capable of reaching ultra-high speeds. We demonstrate the basic building block ONNs — a single neuron perceptron — by mapping synapses onto 49 wavelengths to achieve an operating speed of 11.9 x 109 operations per second, or Giga-OPS, at 8 bits per operation, which equates to 95.2 gigabits/s (Gbps). We test the perceptron on handwritten-digit recognition and cancer-cell detection — achieving over 90% and 85% accuracy, respectively. By scaling the perceptron to a deep learning network using off-the-shelf telecom technology we can achieve high throughput operation for matrix multiplication for real-time massive data processing.

Photonic generations of millimeter-wave (mmW) frequencies (30 GHz – 300 GHz) have been attracted more and more interest for applications in 5G and beyond wireless networks. To generate high-quality mmW signals, it requires optical sources with ultra-narrow optical linewidth and low relative intensity noise (RIN). In recent years, we have demonstrated InAs/InP quantum dot / dash (QD) multi-wavelength lasers (QD MWLs) around 1550 nm with the frequency spacing from 10 GHz to 1000 GHz and output power of up to 50 mW. Those QD MWLs have low RIN, ultra-narrow optical linewidth, small timing jitters, compact size, low power consumption and the ability for hybrid integration with silicon substrates. As examples we present a monolithic dual-wavelength (DW) DFB laser based on synthesized aperiodic gratings on InAs/InP QD gain medium and its application as an optical beat source for mmW signal generation. The QD DW-DFB laser is capable of generating spectrally pure mmW signals between 46 GHz and 48 GHz with the 3-dB RF beating linewidth of less than 16 KHz and the RIN of -158 dB/Hz from 10 MHz to 20 GHz. By using this QD DW-DFB laser, we have experimentally demonstrated a multi-gigabit/s mmW radio-over-fiber (mmW-RoF) communication system operating at 47 GHz with 16QAM, 32QAM and 64QAM modulated signals over single mode fiber (SMF) in terms of clear eye and constellation diagrams. We have achieved an optical-heterodyne mmW-RoF system with broadband 4-meter wireless links through 25.22-km SMF featuring a high bitrate of 24-Gbit/s (64QAM × 4-GBaud) using a QD DW-DFB laser.

An SDN reconfigurable metro-access network based on modular photonic integrated ROADM nodes with edgecomputing for beyond 5G application is demonstrated. Multi-degree switching ROADM nodes are used at the metrocore level, while access network is constituted by low-cost 2-degree ROADM nodes. Network scalability per node is met via a modular design where new modules are added in a pay-as-you grow manner to meet capacity demands. We present PIC for wavelength selective switches used in the metro-core network. Two distinct integration approaches i.e. monolithic on InP and hybrid integration of SiPh with InP are followed to enable low loss switching.

In this work, a novel smart quenching approach for a Geiger-mode single-photon avalanche diode is proposed. The avalanche photodiode is connected in series with a metallic filamentary resistive switch (MFRS). The hysteresis behavior of the MFRS makes it suitable to operate as a quenching resistor. Initially the MFRS is in the off state and it quenches an avalanche event triggered by an incident photon. After quenching, the MFRS switches to the low-resistance on-state, which reduces the R-C time constant of the recharging process. A sharp avalanche pulse shape, continuous detection, and fast detection speed have been achieved. Our observations are consistent with a model where the MFRS adaptively changes its resistance state from high to low during quenching and recharging.

This Conference Presentation, “Wavelength-division-multiplexing-based electronic-photonic integrated circuits for high-performance data processing and transportation,” was recorded for the Photonics West 2021 Digital Forum.

Plasmonic metasurfaces offer a new paradigm for the design of optoelectronic devices. We discuss nanoscale device ideas that exploit the optical field enhancement and confinement provided by such metasurfaces to achieve performance benefits. Applications to modulators, photodetectors, phased arrays, high-harmonic generation, and non-linear optics are discussed.

Recent progress is nanoscale photonics is driven by the physics of Mie resonances of high-index dielectric nanoparticles that provides a novel platform for localization of light in subwavelength photonic structures and opens new horizons for metamaterial-enabled photonics, or metaphotonics. We introduce a novel physical mechanism for achieving giant quality-factors (Q-factors) in finite-length periodic arrays of subwavelength optical resonators. The underlying physics is based on resonant coupling between the band-edge mode and another standing mode in the array and the formation of localized states with dramatically suppressed radiative losses.

We experimentally demonstrate the feasibility of the use of integrated linearly uncoupled resonators, which are coupled solely through the nonlinear interaction, to selectively enhance or suppress nonlinear processes. This is exploited to selectively enhance dual-pump spontaneous four-wave mixing while suppressing the parasitic noise associated with single pump spontaneous four-wave mixing processes. A signal-to-noise ratio characterizing the generation of identical photon pairs of more than four orders of magnitude is reported, opening the way to a new class of integrated devices exploiting the unique properties of identical photon pairs in the same optical mode.

Optical phased arrays (OPAs) with the ability of dynamic beam-steering hold great promise for LiDAR applications. In contrast to mechanical scanning, OPAs have the advantage of being capable of agile beam pointing, allowing the multifunctional operation in LiDARs. In this paper, we propose a liquid crystal (LC) tunable OPA to achieve 2D beam steering. This approach enables a LC-tunable beam control in a second axis in addition to an OPA-tuning, thereby achieving 2D beam steering at a single wavelength. The LC-tunable OPA is fabricated using a standard Si photonics process and a LC process common for commercialized LC displays and LC on Si (LCOS) devices. We have fabricated samples of LC-tunable devices and LC-tunable OPA devices for 1D and 2D steering respectively and demonstrated a LiDAR using the 1D steering device. By taking advantage of non-mechanical movement of the device, a target tracking is realized by detecting a person from a camera image and irradiating the steering beam in that direction with more than 10 frames per second. With a faster 2D steering, a 3D target tracking even for multiple targets could be realized in the future.

This Conference Presentation, “An ultra-strong Pockels effect in silicon photonics,” was recorded for the Photonics West 2021 Digital Forum.

This Conference Presentation, “Controlling light-matter interactions at a deep subwavelength nanofocus,” was recorded for the Photonics West 2021 Digital Forum.

This Conference Presentation, “Metasurfaces for holography and light harvesting: new approaches with orbital-angular moment modes and tailored disorder,” was recorded for the Photonics West 2021 Digital Forum.

This Conference Presentation, “ Topological plasmonics: watching plasmonic skyrmions,” was recorded for the Photonics West 2021 Digital Forum.