This PDF file contains the front matter associated with SPIE Proceedings Volume 10921, including the Title Page, Copyright information, Table of Contents, Author and Conference Committee lists.

Optical frequency combs are the enabling technology of a myriad of areas of science and engineering, where the line frequency spacing plays a fundamental role in their areas of application. Here, we review recent research work on the proposal and experimental demonstration of a set of signal processing techniques based on linear phase-only operations, inspired by the theory of the Talbot effect. These are aimed at re-distributing the energy of periodic spectral waveforms, such as frequency combs, achieving an arbitrary control of their line spacing. The energy-preserving nature of such techniques provides them with the capability of mitigating the noise of the signals of interest in a deterministic way, even allowing for the detection and measurement of signals entirely buried under the noise floor.

Microwave photonic true time delay lines (TTDLs), which can introduce multiple progressive time delays, are one of the basic building blocks of microwave photonic systems. Offering intrinsically low loss, ultra-wide operation bandwidth, and strong immunity to electromagnetic interference, photonic TTDLs have wide applications for phased array antennas (PAAs), microwave photonic filters, analog-to digital or digital-to-analog conversion, and arbitrary waveform generation. Here, we demonstrate significantly improved performance of a microwave photonic TTDL based on optical micro-comb generated by an integrated microring resonator with a free spectral range (FSR) of ~49 GHz, which performs as a highquality multi-wavelength source for the TTDL. The broadband (>100 nm) optical micro-comb achieved with a record low FSR of 49 GHz results in an unprecedented record high channel number (81 over the C band) the highest number of channels for an integrated comb source used for microwave photonic processing. As compared with conventional TTDLs implemented by discrete laser arrays, the system cost, size, and complexity of our TTDL can be significantly reduced. We investigate the performance of a phased array antenna based on our TTDL and show that the large channel count leads to a high angular resolution and wide tuning range of the beam steering angle. This demonstrates the feasibility of our approach as a competitive solution toward implementing integrated photonic true time delays in radar and communications systems.

We demonstrate an 80-tap radio frequency (RF) transversal filter based on a 49GHz-spacing integrated micro-comb source. By employing a record 80 micro-comb lines, or taps, for the transversal filter, we achieve very high performance including a Q_RF factor more than four times higher than previous results. Our experimental results match well with theory, showing that our transversal filter is a competitive solution to implement advanced adaptive RF filters with high frequency selectivity and reconfigurability, and with potentially lower cost and footprint. This approach is promising for applications in modern radar and satellite communications systems.

Recently, dual mode lasers proved to be interesting sources for radio frequency generation at millimeter wave frequency and beyond, to be used in photonic RoF systems. As the optical modes can eventually be correlated, such sources associate the simplicity of heterodyning technique with the frequency stability. Still, most architectures require active frequency control loop to reach communication requirements to limit frequency drift, and reduce the phase noise of the generated carrier. In this communication, we propose the use of a free running dual mode laser integrated on glass for radio frequency generation. The device is fabricated on an ion-exchanged co-doped Erbium Ytterbium substrate to emit in the C-band. We demonstrate that this device is able to generate an ultra-narrow spectrum radio-frequency carrier, reaching 600Hz spectral linewidth without control loop nor thermal stabilization. As a proof of concept, the device proposed in this work produces a radio frequency at 6.1 GHz which has been evaluated as an electrical carrier in radio transmission experiments. Data rates of several Gbps using complex modulation formats such from BPSK to 64QAM have been successfully tested. The results are compliant with communications standards requirements, validating the use of such a source in Radio over Fibre (RoF) systems. This paper first presents the glass dual-mode laser design, followed by the characterization of the generated carrier to finally present the radio over fiber results.

Chalcogenide glasses, amorphous compounds containing the chalcogens S, Se, or Te, are emerging as ideal materials for nonlinear photonics in the infrared given their large Kerr nonlinearity, minimal two photon absorption, and exceptional broadband optical transparency. In this talk, we will discuss characterization and optimization of optical nonlinearity in chalcogenide glasses via a high-throughput screening method. We further implement the optimized nonlinear chalcogenide media to enable broadband on-chip spectroscopic sensing. Specifically, we demonstrated a supercontinuum source integrated on-chip spectroscopic sensor, where we leverage nonlinear Ge22Sb18Se60 chalcogenide glass waveguides as a unified platform for both broadband supercontinuum generation and chemical detection. This work represents an important step towards realizing a miniaturized spectroscopic sensing system based on photonic chips.

In this communication, we report on the design, fabrication and testing of silicon-nitride-in-insulator (SiNOI) nonlinear photonic circuits for comb generation in silicon photonics and optoelectronics. The low two-photon absorption when compared with crystalline silicon makes the SiNOI an attractive platform for frequency comb generation. Kerr combs have been recently used in terabit per second coherent communications demos. Such devices can overcome the intrinsic limitations of nowadays silicon photonics notably concerning the heterogenous integration of III-V on SOI lasers for both datacom and telecom applications. By using monolithically-integrated SiN-based Kerr frequency combs, the generation of tens or even hundreds of new optical frequencies can be obtained in dispersion tailored waveguides and resonators, thus providing an all-optical alternative to the heterointegration of hundreds of standalone III-V on Si lasers. However, in all the previous SiNOI-based frequency combs, the silicon nitride film is annealed under long and high temperature which made the cointegration with silicon based optoelectronics elusive. The annealing steps used in common SiN fabrication processes are not only incompatible with the front-end of line complementary metal-oxidesemiconductor processes, but also costly and long and thus an important cost factor in non-CMOS compatible processes. In our work, we present the fabrication and testing of an annealing-free and crack-free SiNOI. Notably, a 800-nmspanning (1300-2100 nm) frequency comb is generated using 740-nm-thick silicon nitride featuring full compatibility with silicon photonics integrated circuits. This work constitutes a new, decisive step toward time-stable power-efficient Kerr-based broadband sources featuring full process compatibility with Si photonic integrated circuits (Si-PICs) on CMOS-lines.

Second order nonlinearities are inhibited in centrosymmetric crystals, like silicon. However, in the last ten years many attempts have been carried out to induce second order nonlinear susceptibility applying a stressing layer of silicon nitride on the top of a silicon waveguide. Succesful experiments showed both Second Harmonic Generation (SHG) or electro-optic modulation in strained silicon waveguide. In order to develop new devices, a full comprehension of the origins of such a nonlinearity is needed. In fact, a lot of estimations of the second order nonlinear coefficient have been given, all different from each other and, in some cases, even contradictory. In this work, we perform SHG in multimodal phase-matched silicon waveguides. We propose a way to individuate the origin of the nonlinearity, discriminating among the break of the centrosymmetry, the presence of charged states at the interfaces between silicon and silicon nitride and the overlap of the optical mode with the silicon nitride. We estimated a value of the second order nonlinear coefficient of 0.5 pm/V, demonstrating that it results from the coupling of the silicon third order nonlinear coefficient with the electric field induced by the presence of the trapped charges at the core/cladding interface. We also show preliminary results on SHG in strained silicon microring resonators. Our results open the door to interesting applications, going from broad frequency conversion, to generation of quantum states of light, up to the generation of octave spanning frequency comb based on second order nonlinearities.

We present silicon-germanium on silicon waveguides as a suitable platform for on-chip supercontinuum generation in the mid-infrared. We report low propagation loss (<0.4dB∕cm) in the 3.5-5 μm range, leading to an octave spanning supercontinuum extending up to 8.5 μm with a high average power of more than 10 mW on-chip. Furthermore, we present the addition of a chalcogenide cladding layer as a simple post-processing technique to fine tune the waveguide dispersion which, in turn, governs the properties of the generated supercontinuum.

Integrated nanophotonic component design processes are often constrained by computational resources. Advances in simulation and optimization tools have allowed more efficient exploration of larger design spaces. These developments reduce the time-consuming and intuition-limited effort of encoding physical insights into the design structure. However, we argue that efficient optimization is only part of the solution to tackle larger multi-parameter design spaces. Finding patterns in such a space can be more valuable than identifying the individual optima alone. This is particularly true when transitioning from simulation to real device fabrication, where considerations such as tolerance to fabrication imperfections, bandwidth, etc. take an important role but are ignored at the optimization stage. The elucidation of patterns in a complex design space enables efficient identification of designs addressing these additional considerations. As an example, in this presentation we demonstrate how limited data collected from the optimization process of a multisegment vertical grating coupler can be used to identify such patterns through the application of machine learning techniques. The identified patterns, some more interpretable than others, can be used in multiple ways: from speeding up the remaining optimization process itself to gaining insight into the properties of an interesting subset of designs. Together those insights offer a significantly clearer picture of the design space and form the basis for making much more informed decisions on the final designs to be fabricated.

Chemicals are best recognized by their unique wavelength specific optical absorption signatures in the molecular fingerprint region from λ=3^-15μm. In recent years, photonic devices on chips are increasingly being used for chemical and biological sensing. Silicon has been the material of choice of the photonics industry over the last decade due to its easy integration with silicon electronics as well as its optical transparency in the near-infrared telecom wavelengths. Silicon is optically transparent from 1.1 μm to 8 μm with research from several groups in the mid-IR. However, intrinsic material losses in silicon exceed 2dB/cm after λ~7μm (~0.25dB/cm at λ=6μm). In addition to the waveguiding core, an appropriate transparent cladding is also required. Available core-cladding choices such as Ge-GaAs, GaAs-AlGaAs, InGaAs-InP would need suspended membrane photonic crystal waveguide geometries. However, since the most efficient QCLs demonstrated are in the InP platform, the choice of InGaAs-InP eliminates need for wafer bonding versus other choices. The InGaAs-InP material platform can also potentially cover the entire molecular fingerprint region from λ=3^-15μm. At long wavelengths, in monolithic architectures integrating lasers, detectors and passive sensor photonic components without wafer bonding, compact passive photonic integrated circuit (PIC) components are desirable to reduce expensive epi material loss in passive PIC etched areas. In this paper, we consider miniaturization of waveguide bends and polarization rotators. We experimentally demonstrate suspended membrane subwavelength waveguide bends with compact sub-50μm bend radius and compact sub-300μm long polarization rotators in the InGaAs/InP material system. Measurements are centered at λ=6.15μm for sensing ammonia.

For the first time, a high sulfur content polymer has been photo-bleached to yield an optical waveguide suitable for mid-wave infrared (MWIR) photonics. The polymer was synthesized by inverse vulcanization of elemental sulfur with the organic monomer 1,3-diisopropenylbenzene (DIB) to produce the polymeric material poly(sulfur-r-(1,3-diisopropenylbenze)) (poly(s-r-DIB)). This glassy, red polymer is available in bulk/solution form and affords easy processability. This novel polymer is extremely low cost, displays high refractive index (1.8), and is transparent at most short-wave infrared (SWIR) and MWIR wavelengths. These attributes make it highly desirable and a more suitable substitute to commercially available alternatives, such as chalcogenide glasses, which can be toxic, expensive and difficult to process. In this work, we demonstrate that photo-bleaching of the polymer occurs when exposed to intense UV light, inducing a change in the refractive index. The index can thereby also be tuned by changing the exposure parameters and the ambient atmospheric conditions. This phenomenon was used to fabricate optical waveguides suitable for SWIR and MWIR wavelengths. Optical characterization of the waveguides was performed to measure the propagation losses of the material. The low cost of the material and the facile nature of the fabrication and processing enables high reproducibility making this system desirable for a multitude of photonic applications such as on-chip spectroscopy and frequency combs.

In fiber optic communication systems, tunable optical add-drop filters are needed for wavelength selection and wavelength channel (de)multiplexing. Ideally filters should possess wide dynamic tuning range, narrow bandwidth and high sidelobe-suppression capabilities. In this contribution, we show that such filters can be obtained with microring resonators incorporating liquid crystals as core materials. Special thermotropic liquid crystal blends were developed such that, in their isotropic phase, to be able to provide large Kerr constants, low loss from visible to infrared and sub-microsecond response time. These blends were used in the design of Vernier type filters with 2 to 4 serially coupled ring resonators. The filters were designed by means of FEM simulations, to operate in C-band. Parameters such as the number of rings, ring geometry and light coupling geometry were optimized to obtain large free spectral range and wide tuning range, narrow bandwidth, high sidelobe-suppression and low insertion loss. Moreover, the influence of fabrication tolerances on the device optical loss was considered in the design. The designed filters were fabricated on silicon wafers by micromachining processes. In particular, a special wafer assembly process was developed to ensure improved wafer bonding and low insertion loss. Experimental results revealed loss optimized tunable wavelength reconfigurable filters with add / drop functions of large free spectral range (FSR) of about 50 nm, wide dynamic tuning range of about 1 FSR and fast (sub-microsecond) tuning capabilities. Additionally, we show that these devices can be useful for other WDM applications, e.g., switching in C-band or visible range.

In this paper, we present a hybrid process to make a flexible photonic circuit. The photonic circuit is fabricated on a Silicon substrate with PECVD Silicon Nitride (SiN) as a waveguide layer on an oxide layer. The SiN waveguide circuit is fabricated using conventional lithography and dry etching followed by Si substrate thinned down to 10micrometer. The thin-film photonic circuit integrity after wafer-thinning and layer transfer is characterized by the waveguide performance, grating coupler efficiency and ring resonator performance. We observe no degradation in device and circuit performance. We present detailed process flow, SiN-to-PDMS embedding process and detailed device characterization.

Due to small refractive change, it is difficult to obtain high confined glass integrated waveguide. A proposed solution is to make firstly a planar waveguide by ion exchanged and then to use an optical grade dicing to realize two separated grooves. The cutting and the polishing of the glass are made at the same time. Monomode ridge waveguide with a smallest width of 4 μm and a height of tens micrometers are characterized, either in the near-infrared domain or in the visible domain. The propagation losses can be smaller than 1 dB/cm with fiber coupling losses around 2 dB depending on the fiber used to excite the waveguide.

Dynamically encircling an exceptional point (EP) of a non-Hermitian system, in which the parameters are continuously varied around the EP, offers direction dependent conversion into orthogonal eigenstates that is robust to input state variation. The requirement for adiabatic conditions in the encircling, equating to very slow modulation in parameter space about the EP, ultimately results in long path lengths. This proves a strong limitation on the use of passive materials for mode conversion in such systems, as including loss becomes necessary. Thus, in passive converters, output of the converted mode will have very small intensity and be difficult to integrate into larger systems. Here we experimentally demonstrate chiral conversion into orthogonal supermodes by dynamic encirclement of an EP in an active, nonlinear system of two coupled waveguides. The introduction of gain allows for sufficiently adiabatic systems with control of output intensity, equaling or amplifying that of the input signal. This work paves the way for further use of active media in chiral mode converters, as well as the fabrication of semiconductor lasers with direction dependent mode output, more suitable for integration into larger systems.

This paper reports for the first time a high-contrast, low-power reflective color filter employing a phase change material in a waveguide grating with different periods. Refractive index modulation is produced by crystallographic phase transition of Germanium Telluride (GeTe) using an external stimulus, such as heat. Nanostrips of GeTe are used due to their reliable, fast, and reversible phase transitions. These thin nanostrips reduce the total light absorption and yield a vivid, bright reflected color. Moreover, a buried optical waveguide consisting of a silicon nitride (Si₃N₄) core, which was grown between two layers of silicon dioxide (SiO₂) cladding, is placed under these gratings to enhance the color contrast. The waveguide resonance is enhanced using a bottom palladium reflector and GeTe gratings above with different periods. Selective absorption within visible-NIR region that depend on the period of the grating and the phase of the GeTe is introduced within these devices for the first time. A unique anti-reflective coating was also re-introduced to suppress the surface reflection, thus enhancing the color contrast. Vivid reflected red and green colors have been shown for a device with active area of 400 μm². These colors were electrically transitioned to blue and yellow, respectively, for several cycles. We further report that GeTe nanostrips with different cross-sectional areas demonstrate different phase transition behaviors. Thus, several colors were achieved within the same area of the device employing GeTe nanostrips with different periods.

We presented design, growth and fabrication of the InAs/InP quantum dot (QD) gain materials and the basic performance of the Fabry-Perot QD lasers as compared with the quantum-well (QW) lasers with the same doped materials and structures. By using those QDs we have developed several ultra-low intensity and phase noise coherent comb lasers (CCLs). We have used a 25-GHz QD C-band CCL to successfully demonstrate 10.3 Tbit/s (16QAM 56×23 GBd PDM) back-to-back coherent data transmission for coherent networks and 56×50 Gb/s PAM-4 back-to-back transmission with capacity of 2.8 Tbit/s at a symbol rate of 25 GBaud for data center applications.

On-chip light detection is universally regarded as a key functionality that enables myriad of applications, including optical communications, sensing, health monitoring or object recognition, to name a few. Silicon is widely used in the micro-electronics industry. However, its electronics bandgap precludes the fabrication of high-performance photodetectors that operate at wavelengths longer that 1.1 μm, a spectral range harnessed by optical communication windows of low fiber attenuation and dispersion. Conversely, Germanium, a group-IV semiconductor as Silicon, with a cut-off wavelength of ~1.8 μm, yields efficient light detection at near-infrared wavelengths. Germanium-based photodetectors are mature building blocks in the library of silicon nanophotonic devices, with a low dark-current, a fast response, a high responsivity and low power consumption with an established fabrication flow. In this work, we report on the design, fabrication and operation of waveguide pin photodetectors that advantageously exploit lateral Silicon/Germanium/Silicon heterojunctions. Devices were fabricated on 200 mm silicon-on-insulator substrates using standard micro-electronics production tools and processes. This photodetector architecture takes advantage of the compatibility with contact process steps of silicon modulators, thereby offering substantially reduced fabrication complexity for transmitters and receivers, while providing improved optical characteristics. More specifically, at a lowbias reverse voltage of -1 V, we experimentally achieved dark-currents lower that 10 nA, a device photo-responsivity up to 1.1 A/W, and large 3-dB opto-electrical bandwidths over 50 GHz. In addition, high-speed data rate transmission measurements via eye diagram inspection have been conducted, with pin photodetector operation at the conventional 10 Gbps up to the future 40 Gbps link speeds.

Phase modulators are key building blocks for Photonic Integrated Circuits (PICs). Si modulators based on plasma dispersion suffer from spurious amplitude modulation and high insertion losses. Pockels effect has been explored for more efficient phase modulators. However, Si doesn’t exhibit Pockels effect due to its centrosymmetric structure. Co-integration of thin-film electro-optic materials possessing a strong linear electro-optic coefficient on Si has therefore been proposed as an ideal alternative for more efficient phase modulators. Strongly electro-optic thin films of ferro-electric Lead Zirconate Titanate (PZT) grown on Si waveguides allow for Hybrid PZT/Si phase modulators. We present here a TE/TM electro-optic modulator with bias-free operation, bandwidths beyond 10Ghz, and negligible spurious amplitude modulation. The modulator is a phase shifter which comprises of straight Si waveguides and thin films of PZT spin-coated on the waveguides. The phase shifters were experimentally characterized by beating the modulated signal with an external acousto-optic modulator and evaluating the ratio between both signals. This experiment enables fast and easy characterization of phase modulators as proof of concept.

The practical combination of quantum cryptography and classical communications will require convergence of their technologies. In this pivotal time where both fields are transitioning towards photonic integrated architectures, it is essential to develop devices that fully leverage their hardware compatibilities, while still addressing the key issues of cost reduction, miniaturization and infrastructure energetic footprint, essential for future high- bandwidth, low-latency networks. Here, we address these issues by developing an on-chip transmitter consisting of just 3 building blocks but capable of transmitting both quantum encrypted photons and classical multi-level modulation signals. By combining optical injection locking and direct phase modulation we are able to encode pulse trains with multiple levels of differential phase, without the need of high-speed electro-optic modulators and their associated power footprint. We generate return-to-zero differential phase shift keying signals with up to 16 distinct levels. Moreover, we demonstrate multi-protocol quantum key distribution delivering state-of-the-art secure key rates. Our on-chip transmitter will facilitate the flexible combination of quantum and classical communications within a single, power-efficient device that can readily be integrated in existing high connectivity networks.

We recently presented a novel retinal projection concept based on the combination of integrated optics and holography. Our lens-free optical system uses disruptive technologies to overcome the limitations of current devices such as a limited field-of-view and bulky optical assemblies. An integrated optical network of Si₃N₄ waveguides has been designed in the visible range in order to control the intensity of an optical field originating from an emissive point distribution (EPD) at a glass surface. In addition, the phase and orientation of the optical field are controlled by incorporating a pixelated holographic layer. The Si₃N₄ waveguides are transparent, allowing ambient light to pass through the device for augmented reality applications. This study focuses on the design of the components used for the optical circuit at λ = 532 nm (hologram laser recording wavelength): single-mode waveguides, bent waveguides, cross-talk, diffraction grating couplers, MMI splitters (MultiMode Interference) and directional couplers. The parameters of the components are optimized with various numerical methods. Furthermore, an optical circuit used as the first test structure is presented. An optical set-up based on a goniometric configuration has been built to characterize the efficiency of our components with a particular focus on the angular properties. Future work will focus on the hologram recording process that will involve interferences between the EPD output beams and free-space planar light waves.

Due to their unique vibrational/rotational frequencies in the mid infrared (MIR) fingerprint region, which scans from 500 to 1500 cm^-1, molecules can be assuredly identified and quantified. Thus, integrated on-chip mid infrared spectroscopic systems, with low power consumption and high performance, would show great value for numerous applications, such as medical diagnosis, astronomy, chemical and biological sensing or security. Different solutions can be envisioned, such as Fourier-Transform spectrometers, echelle gratings, or arrayed waveguide gratings (AWG). The integrated spatial heterodyne Fourier-Transform spectrometer (SHFTS) shows relaxed fabrication tolerances while applying a phase and amplitude correction algorithm. Meanwhile, it provides high optical throughput and high spectral resolution compared with AWG or echelle gratings. However, up to now in the literature, most of the reported integrated Fourier-Transform based spectrometer is based on silicon-on-insulator operating in the near infrared typically at 1.55 μm wavelength. Thereby the development of integrated Fourier-Transform spectrometers operating in the MIR covering the wide fingerprint region is highly desirable. In this work, we experimentally demonstrate the first duel polarization SHFTS operating in the mid infrared beyond 5 μm wavelength. The fabricated FTS, which is based on the graded-index Ge-rich SiGe platform, contains 19 Mach-Zehnder interferometers with a linearly increasing path difference. A spectral resolution better than 15 cm^-1 has been demonstrated within an unprecedented spectral range of 800 cm^-1 (from 5 to 8.5 μm wavelength).

We will review the development in the last decade of discrete beam combiners (DBC), phase sensors based on the propagation of light in photonic lattices. The latest results on the development of DBC for astronomical applications will be presented, along with a new application for the complete tomography of modes at the tip of a multi-mode fiber. The possible use of the DBC in monitoring and controlling modal instabilities in high power lasers will be discussed.

Functional oxides are a very interesting class of materials due to their singular properties. Material engineering is commonly employed to tune and manipulate such properties at will, thus being functional oxides often used to build active reconfigurable elements in complex systems. In this regard, Yttria-Stabilized Zirconia (YSZ) stands as an interesting material since it has stable thermal and chemical properties and offers a wide transparency range from the visible to the mid-IR wavelength range. Moreover, it has a moderate refractive index of 2.1 which provides a good potential for the development of low-loss waveguides when grown over a low contrast substrate. While these optical properties are very interesting for various applications, including on-chip optical communications and sensing, YSZ has remained almost unexplored in photonics. In this regard, we recently demonstrated YSZ waveguides with propagation losses as low as 2 dB/cm at a wavelength of 1380 nm³. Based on the encouraging preliminary results, we have recently explored the possibility to introduce active rare-earth dopants into YSZ waveguides to demonstrate on-chip optical amplifiers based on YSZ. This work explores the introduction of Er³⁺ ions using a multilayer approach deposited by pulsed laser deposition (PLD) technique, providing outstanding luminescence around λ = 1.55 μm, in correspondence with C-band of telecommunications. Such active layers have been grown onto different platforms, including SiN_x and sapphire. The optical properties of Er-doped YSZ waveguides under resonant pumping and its propagation losses will be discussed in this paper. These results pave the way towards the implementation of new rare-earth-doped functional oxides into hybrid photonic platforms in a customized and versatile manner, adding novel light amplification functionalities.

Silicon photonics technology has demonstrated, over the years, Photonic Integrated Circuits (PICs) relying on Si or Si3N4 materials that feature advanced functionalities for a wide area of applications. However, the fabrication of such PICs is usually compatible only with Front-End-of-Line (FEOL) processes that render very difficult post processing of the involved chips towards providing efficient interfaces with optical sources. This is a major problem for the next generation photonic circuits that are expected to co-integrate III-V laser sources on the Si substrate in a monolithic way, as the coupling interface between the active and the passive part of the PIC should be developed after the epitaxy and the fabrication of the lasers. In this work, we report on the development of a novel Silicon Rich Nitride (SRN) material with low stress and high refractive index (n<3.16), close to that of InP and InGaAsP which are commonly utilized for the laser sources. The SRN has been characterized with spectroscopic ellipsometry and Fourier-Transform Infrared Spectroscopy for estimation of complex refractive index and hydrogen content in the film. Based on this material, a trilayer stack has been developed for the formation of waveguides compatible with the Back-End-of-Line (BEOL) processes, while propagation losses have been extracted through cut-back measurements. These experimental results were then inserted as input parameters in 2D- and 3D-FDTD simulations for the design of efficient interfaces between III-V lasers and Si3N4 waveguides providing coupling efficiencies that can reach 83.81% and back-reflections of 0.032%.

The work that I will present focuses on the fabrication of non-perturbing E-field sensors based on the electro-optic effect. Lithium Niobate, combined with photonic crystals can increase considerably the material sensitivity to electric fields leading to ultra-compact devices. The target structure exhibits high sensitivity, THz bandwidth ans micrometric spatial resolution. In addition, since the sensor is only fabricated with dielectric materials, it does not perturb the electric field to be measured. In my presentation I will focus on the simulation, fabrication and characterization of the fiber-tip electric field sensor. We have performed simulations in order to study the feasibility where the different fabrication errors are considered.The fabrication is divided into two parts: a first one where we overcome the problem of micromachining photonic crystals on thin film lithium niobate of 700 nm of thickness. In the second part, the integration of the photonic crystal within the fiber facet will be explained. Optical characterization and electrical performance will be shown verifying its different features such as spatial resolution, linearity, electrical sensitivity and bandwidth. The fabricated device shows performances nevev achieved beofre and open up a high spectrum of applications like cold plasma, military, and telelcommunications applications.

Silicon-Nitride based Photonic Integrated Circuits (PICs) broaden the application scope of PICs outside of telecommunications where it originated from, since the wavelength range over which a waveguide can be designed matches for instance biophotonic applications usually working in the VIS (400-700nm) and NIR (700-1000nm) range. In this paper we show the latest results our silicon-nitride based sensor platform, that consist of an array of several types of interferometric sensors (Microring resonators, Mach-Zehnder interferometers), that are either used as refractive index, absorption or fluorescence sensors. We show the trade-offs between the different sensor types and show why an asymmetric MZI improves the sensitivity of the sensor platform over the MRR with over a factor of 10 down to the 10^-8 RIU level. Furthermore we show that using flip-chipped VCSELs as integrated light source a low cost, disposable device is made. For desktop purposes we show how light sources are fiber coupled to the sensing platform creating a high end measurement system. The complete readout system allows for measuring multiple sensors on the chip, enabling multi-analyte measurements as well as improve the total stability of the measurement platform by using on-chip references. Finally we show an overview of measurement results where the sensor platform is functionalized using different interaction layers both local as well as wafer- scale. The results that the sensor platform can be used in for example liquid (blood and saliva) analysis as well as bacteria detection. The platform can be extended with a microfluidic interface for interaction of the optical layer and fluidics. An added integrated on-chip spectrometer allow additional functionality to the presented sensing platform.

Coating of high-Q whispering gallery mode micro-resonators is typically performed in order to add the functionalities of the coating material to the unique properties of this type of resonators. Silica microspheres or microtoroids are typically used as high-Q cavity substrate on which a functional film is deposited. In order to effectively exploit the coating properties a critical step is the efficient excitation of WGMs mainly contained inside the deposited layer. We developed a simple method able to assess whether or not these modes are selectively excited. The method is based on monitoring the thermal shift of the excited resonance, which uniquely depends on the thermo-optic coefficient and on the thermal expansion coefficient of the material in which the mode is embedded. We applied this technique to the case of a SU-8 layer deposited on a silica microsphere. Main tests were performed around the wavelength of 770 nm because of potential application in biochemical sensing requiring low light absorption in aqueous environment. We show that by using integrated waveguides made with SU-8 polymer (rather than silica fiber tapers) we can fulfill the proper phase matching conditions thus exciting the fundamental WGM mainly confined in the coating. A further proof of the validity of the approach is obtained assessing the free spectral range of the excited modes which depends on the refractive index of the material in which the mode is confined.

Recently, semiconductor nanowires (SCNWs) have received much attention due to their crucial role in physiochemical science and their high prospect for essential applications in advanced devices such as solar cells, light-emitting-diodes, transistors and bio/chemical sensors. Vertically-aligned silicon nanowires (SiNWs) platform is considered as a strong candidate for advanced devices because of the high volume-to-surface area ratio as well as the high aspect ratio originating from the vertical structure. The CMOS compatibility of such a platform allows for cheap commercial manufacturing of nanophotonic integrated circuit. Nanowire diameter is usually on the order of several nanometers and is comparable to the Debye length and this often results in much larger sensitivity than their thin film. In this work, we design a vertically-aligned SiNW gas sensor optimized to detect carbon monoxide (CO) gas at the midinfrared (MIR) range. SiNWs of diameters of only 200 nanometers are grown on Si wafers. According to Liao et al, thin nanorods have a significantly better sensing performance than thick nanorods in the detection of C₂H₅OH and H₂S (100 ppm) in air. In addition, (MIR) gas sensing is very useful and user friendly as the gases are directly detected when they flow through the active sensing region of the sensor with no required human interaction with the dangerous gases. Finite difference time domain (FDTD) simulations are performed to verify the results and a comparison between the FDTD results and the experimental ones are held.

3D photonic integration introduces a new degree of freedom in the design of photonic integrated circuits (PICs) compared to standard 2D-like structures. Novel applications such as large-scale optical switching matrices, e.g. for top-of- rack cross connect switches in data centers, benefit from the additional design flexibility due to their waveguide crossing-free architecture and compact footprint. In this work, a novel 3D 4×4 multi-mode interference coupler (MMI) based on HHI’s polymer-based photonic integration platform PolyBoard is presented. The fabrication process of the PolyBoard platform allows for the realization of vertically stacked polymer waveguide layers. Cascading two of the presented 3D 4×4 MMIs will form the building block of future large-scale 3D switching matrices. The 3D 4×4 MMI structure comprises two waveguide layers separated by a distance of 7.2 μm, with two input and two output waveguides in each layer, and a multimode interference (MMI) section in between. The vertical MMI section serves as the interconnection between the different waveguide layers and distributes the incoming light from each input waveguide across the four output ports of the 4×4 MMI. Design rules and fabrication methodology of these novel structures are presented in detail. Preliminary measurements demonstrate the proof-of-concept indicating an insertion loss below 9.3 dB, including fiber-chip coupling loss and the 6 dB intrinsic loss.

We demonstrate an integrated photonic platform for control of complex atomic systems. The platform includes multiple waveguide layers and a suite of passive photonic circuit components supporting a wavelength range from 370-1100 nm. In particular, we demonstrate a novel dual-layer vertical grating coupler used for efficiently directing visible light to precise positions above the chip surface. These circuits are compatible with traditional CMOS fabrication techniques and are well suited for improving the scalability of quantum information processing systems based on trapped-ion technology. A chip-scale waveguide platform at visible wavelengths could also prove useful in a variety of bio-photonic and sensing applications requiring precise light delivery or readout in a compact footprint.

We present principles of leaky-mode photonic lattices explaining key properties enabling potential device applications. The one-dimensional grating-type canonical model is rich in properties and conceptually transparent encompassing all essential attributes applicable to two-dimensional metasurfaces and periodic photonic slabs. We address the operative physical mechanisms grounded in lateral leaky Bloch mode resonance emphasizing the significant influence imparted by the periodicity and the waveguide characteristics of the lattice. The effects discussed are not explainable in terms of local Fabry-Perot or Mie resonances. In particular, herein, we summarize the band dynamics of the leaky stopband revealing principal Bragg diffraction processes responsible for band-gap size and band closure conditions. We review Bloch wave vector control of spectral characteristics in terms of distinct evanescent diffraction channels driving designated Bloch modes in the lattice.

Bragg filters stand as a key building blocks of the silicon-on-insulator (SOI) photonics platform, allowing the implementation of advanced on-chip signal manipulation. However, achieving narrowband Bragg filters with large rejection levels is often hindered by fabrication constraints and imperfections. Here, we present a new generation of high-performance Bragg filters that exploit subwavelength and corrugation symmetry engineering to overcome bandwidth-rejection trade-off in state-of-the-art implementations. We experimentally show flexible control over the width and depth of the Bragg resonance, unlocking new tools for the implementation of notch filters with arbitrary bandwidth and rejection level. These results pave the way for the implementation of high-performance on-chip wavelength filters with a great potential for nonlinear-based applications, e.g. next generation Si-based photon-pair sources for quantum photonic circuits.

Thin-film polymer-on-silicon modulators are efficient devices which have shown potential for integration scalability due to chromophore-based electro-optic constant engineering. Assembling them into hybrid silicon-photonics integrated circuits poses an interesting challenge in terms of bandwidth and footprint. Accordingly, we propose the first, to the best of our knowledge, sub-wavelength silicon tapered structures to couple light vertically from a polymer film platform to a silicon-on-insulator chip. By designing horizontally tapered and longitudinally segmented waveguides in the subwavelength regime to couple light vertically, we can overcome the bandwidth limitations of grating couplers while still have considerable footprint reduction when compared to continuous linearly tapered evanescent vertical coupling. Our simulation results show that silicon-on-insulator-compatible linearly tapered segmented waveguides offer losses bellow 0.5 dB in the C and L bands with four times smaller coupling length than their continuous counterpart. Preliminary studies show that there is good horizontal misalignment tolerance up to 1.5 micrometers.

Electrically-driven nanoscale light sources are imperative in the design on nanophotonic circuits and applications. We will discuss the direct excitation of waveguided modes of a metamaterial slab consisting of array of plasmonic nanoparticles using electron tunnelling effects. The large flux of hot electrons makes the tunnel junctions highly reactive, providing opportunities for designing hydrogen and oxygen sensors. Tunnel-junction based nanoscale light sources provide numerous opportunities for free space and integrated optics applications.

We report room temperature plasmonic nanolasers with low threshold on the order of 10 kW cm-2 corresponding to a pump density in the range of modern laser diodes. We systematically study their key parameters, including physical size, threshold, power consumption and lifetime and analyze these to determine a set of laws which suggest that plasmonic lasers can be more compact, faster with lower power consumption than photonic nanolasers when the cavity size approaches or surpasses the diffraction limit. Our study clarifies the long-standing debate over the viability of metal confinement and feedback strategies in laser technology and identifies situations where plasmonic lasers can have clear practical advantage.

Based on magnetooptic Fourier modal method (MOaRCWA) simulations, both in 2D in 3D, we have studied the magnetoplasmons in plasmonic nanostructures, such as InSb within the THz spectral region. One of only few possibilities how to impose nonreciprocity in guiding subwavelength structures is to apply an external magnetic field (mainly in the Voigt configuration). In such a case, one-way (nonreciprocal) propagation of SP is not only possible but may bring many interesting phenomena in connection with magnetoplasmons (MSP). We have developed an efficient 2D and 3D numerical technique based on MO aperiodic rigorous coupled wave analysis – MOaRCWA. In our in-house tool, the artificial periodicity is imposed within a periodic 1D and 2D RCWA methods, in the form of the complex transformation and / or uniaxial perfectly matched layers. We have combined the MOaRCWA simulations with (quasi)analytical predictions in order to study MSP performance of various plasmonic nanostructures, such as basen on a highly-dispersive polaritonic InSb material, in the presence of external magnetic field. Here, Voigt MO effect can be used to impose nonreciprocity (one-way propagation) bringing new interesting phenomena in connection with MSP. We have successfully applied our 2D and 3D numerical MOaRCWA technique to several interesting structures, such as THz filters with magnetooptical Bragg grating, a combined 3D InSb - hybrid dielectric-plasmonic slot waveguide structure, etc. The obtained results will be discussed and the perspective will be given.

Plasmonics have been identified as an ideal platform for ultra-sensitive, label-free biosensors mainly due to the high field confinement on a metal-dielectric interface and the resulting strong light-matter interaction offered by surface plasmon resonances (SPRs) that can be entirely exposed to test analytes. Well-established SPR-based biosensors exploiting propagating SPRs yield superior specifications regarding bulk sensitivity compared to localized counterparts leading to already commercial available sensor devices. However, most of these systems require bulky prism-based configurations to couple light into the Surface Plasmon Polariton (SPP) mode impeding system miniaturization. In addition, SPR-based sensors suffer from intrinsic high propagation losses restricting the potential for multiple on-chip functionalities. In this context, co-integration of plasmonics with a low-loss photonic platform emerges as a viable solution towards highly sensitive, low-loss and small footprint optical sensors. In this work, we present an ultra-compact, interferometric plasmonic sensor co-integrated on a TiO₂ photonic waveguide platform. The device consists of two access TiO₂ photonic waveguides separated by a gold-based metal stripe which is located on top of an appropriately shorter TiO₂ waveguide layer. Two metal/insulator interfaces are formed at the top (sensing arm) and bottom surfaces (reference arm) of the metal able to support SPP modes which upon excitation through the input photonic waveguide propagate along the two metal surfaces and interfere at the output waveguide realizing a single-arm Mach-Zehnder Interferometer. After optimization of the device in aqueous environment, we achieved sensitivity values as high as 2430 nm/RIU at near-infrared spectrum region for a 65 um long plasmonic stripe.

We analyzed regular polygonal ring resonators based on multi-mode waveguide using finite-difference time-domain simulation. It consists of the regular polygonal ring waveguide, total internal reflection mirror, and MMI coupler. In general, multi-mode waveguide-based resonator is difficult to use as sensors because of poor output characteristics. By using the low reflectance of the higher-order mode compared to the fundamental mode in the TIR mirror, we designed a regular polygonal ring resonator that can be used as sensors even when a multi-mode waveguide is used instead of a single-mode waveguide. In fabrication, the multi-mode waveguide has a wider line width than the single-mode waveguide, which reduces the process cost and enables mass production. The width and height of the multi-mode waveguide are designed to be 2.5 μm and 2 μm, respectively using SU-8 polymer. The regular hexagon ring resonator shows the highest Q-factor of 1.03×10⁴ among the various regular polygonal ring resonators.

In this paper, we designed hexagonal ring resonator using localized surface plasmon resonance (LSPR) phenomenon to enhance the sensitivity which is a significant factor in bio-chemical sensors. We used a hexagonal ring resonator structure to eliminate the bending loss which is one of the prime factors affects sensitivity. The sensing area of the hexagonal ring resonator with LSPR is deposited metal nanoparticle on cladding which makes difference with general sensing region of the hexagonal ring resonator. In this sensing region, the wavelength of light should be longer than the size of the nanoparticle because the metal nanoparticle reacts the light in specific condition. The sensitivity of the resonator can be improved with using this phenomenon. We used finite difference time domain (FDTD) methods for theoretical analysis. Also, we optimized the structure to reduce LSPR loss and enhance the sensitivity by adjusting type, size, thickness of the metal nanoparticle. As a simulation result, we verified that sensitivity of hexagonal ring resonator with LSPR can be 2.5 times higher than without LSPR.

The observation of ultrafast signals by expanding them to a time scale that enables the measurement with conventional high-speed systems is of considerable interest in many applications. Usually, a time-lens can be used for this purpose. Like a lens in optics, a time lens expands the signal in time. This can be accomplished by a strong first order dispersion. However, higher order dispersion leads to a distortion of the signal and an integration of elements with a strong first order dispersion is challenging. Here we present a dispersion-less time-lens with an integrated ring resonator. Several replicas of a single input signal are generated by a microring resonator having a free spectral range (FSR) much less than the bandwidth of the input signal. These copies are then subjected to a coupled Mach-Zehnder intensity modulator (MZM) system driven by a single sinusoidal radio frequency (RF) signal to generate copies of the input spectrum. In the time-domain this can be seen as a multiplication of the input signal with a sinc-pulse sequence. The sinc-pulse sequence is tunable by the single sinusoidal radio frequency. By choosing a suitable radio frequency, the signal waveform can be sampled at a different position for each copy, so that an expanded waveform with a configurable stretching factor determined by the input RF can be achieved. This time lens system can be fully integrated into a photonic integrated circuit and requires neither an optical source nor a dispersive medium. In first preliminary experiments we present a sampling rate of around 110 GSa/s.

Structure of a curve slot waveguide based on the Si3N4- SiO2 index contrast is demonstrated by using full vectorial Finite Element Method (FEM). Modal analysis of the device has been performed in quasi TM mode at 1550nm wavelength. Confinement factor and birefringence property of curve slot waveguide has been discussed for variations in slot width. Effective refractive index of the device has also been calculated for the large wavelength range. The waveguide is designed with silicon nitride in complementary to silicon, so it provides low loss due to roughness of wall in large bandwidth range. Photonic Integrated Circuit (PIC) based curve slot waveguide is found a good configuration of waveguide to confine the light in slot region and in terms of material integration and fabrication.

The advancement of fabrication techniques, especially in the field of polymer-based photonic devices, has led to the implementation of novel designs with increased flexibility. In this paper, we propose a polymer-based whispering gallery spiral waveguide, which has been tapered down to nano-dimension for the detection of gold nanoparticles. Gold nanoparticles are being explored extensively in the areas of catalysis, imaging, therapeutic agents, drug delivery in various chemical and medical applications. Though, detection of gold nanoparticles in low concentration with high sensitivity is still a challenge. The proposed structure can be used to detect a single gold nanoparticle. It consists of two interleaved spirals; the inner ends of the spirals are connected by semicircular-arcs of a circle forming an S-shaped structure whereas the outer ends of the spirals serve as input and output ports of the waveguide. By nano-tapering, the center of the spiral, we observe enhanced evanescent field in the tapered region. The interaction of the evanescent field with the gold nanoparticle causes a shift in the characteristic wavelength of the device. The capability of the device to detect gold nanoparticle of different radius (10 nm-100 nm) has been theoretically analyzed. As the shift in the characteristic wavelength depends on the size of the gold nanoparticle, it provides a size selective detection of nanoparticles and this is regarded as an extrinsic size effect. The proposed device has been fabricated by two-photon polymerization based direct laser writing technique.

We demonstrate a polarization diversity optical parametric amplifier (OPA) by a periodically poled LiNbO₃ (PPLN) module for fiber-optic communication systems. We have fabricated the PPLN module which consists of two parallel PPLN ridge waveguide devices to amplify orthogonal polarization components of a signal light independently. The dependence of the parametric gain of each PPLN waveguide on the pump light power was investigated based on a cascaded second harmonic generation (SHG) and OPA process. Both PPLN waveguides showed almost the same parametric gain property, which facilitated the gain equalization between the orthogonal polarization components of the signal light. We successfully performed the polarization-independent OPA by adjusting the quasi-phase-matching wavelengths and the gains of the two PPLN waveguides.

Parametric comparison of ultra-compact few-mode waveguides of three types (strip, rib, and buried) on thin-film Lithium Niobate On Insulator (LNOI) and SOI platforms is presented. Performance of waveguides is compared in terms of waveguide cross-sectional area, mode loss, dispersion, mode-hybridization and power confinement for both quasitransverse electric (qTE) and quasi-transverse magnetic (qTM) modes. It is found that LNOI waveguides exhibit lower dispersion with physical dimensions comparable to that of SOI waveguides. The results are vital in choosing an optimum configuration of few-mode waveguides which is crucial for designing few-mode devices in mode-multiplexing schemes.

The process of an optical signal undergoing a transition between two modes of a photonic structure is referred to as a photonic transition. We show that a signal wave interacting with a free carrier front in a slow light waveguide experiences indirect photonic transitions leading to transmission or reflection from the moving front. Theory and experimental results are presented. The front induced dynamic frequency conversion is also compared to the frequency shifting based on other nonlinear effects like cross-phase modulation and four wave mixing.

Light propagating in waveguides can be manipulated by a moving refractive index front. A linear Schrödinger equation can be used to describe the interaction of a slowly varying signal envelope with a front. In waveguides with weak dispersion usually spatial evolution of the pulse temporal profile is tracked. However, we show that for waveguides with strong dispersion it is beneficial to track temporal evolution of the pulse spatial profile. Simulation examples close to the band edge of a photonic crystal waveguide are presented.

Dielectric microelements with cylindrical and spherical shapes can form an intense sharply focused optical beam, termed “photonic nanojet”. Novel optical devices based on photonic nanojet effect can possibly be used in a broad range of biomedical and photonics applications, including super-resolution microscopy, laser tissue surgery, optical endoscopy and spectroscopy, photo-patterning of thin films, and photovoltaics. The use of photonic nanojets in such devices requires meticulous tuning of several parameters of the focusing element and the light source. In this work, we investigated the multifactorial parameterization of photonic nanojets using finite difference time domain (FDTD) simulations. Input parameters that are investigated include index of refraction (1.2-2.2) and diameter (5-50 μm) of the microfiber. In each simulation, the focusing element was illuminated with a plane wave. For each parameter set, the characteristic parameters of the nanojets, such as lateral resolution, back focal length, and the maximum electric field amplification were calculated. Our results showed that optimal values of electric field amplification, back focal length, and lateral resolution do not occur under the same initial parameterization and tend to trade-off with one another. Detailed results from our investigation will provide insight for future tailoring of nanojet properties of microelements in design of novel optical devices for nanophotonics applications.

Mode Division Multiplexing and De-multiplexing (MDMux / MDDeMux) has been considered a promising technique for increasing link capacity in optical interconnection. One of the most promising structures currently proposed for this application is the Asymmetric Directional Coupler ADC designed to match the propagation constant of the fundamental mode in one guide to that of the higher order modes of the adjacent guides in the coupler. Such an ADC has been used extensively in the literature to demonstrate the mode Mux for up to 16 modes in planar optical circuits. One of the key parameters in the design of such Mux / DeMux is the crosstalk (CT) due to the leakage of an undesired mode in a specific waveguide / channel. The evaluation of this parameter is usually done using numerical techniques such as the BPM or the FDTD. In this work, we apply the Coupled Mode Theory (CMT) on the ADC for the evaluation of the cross talk between guides. The results of the CMT are compared with those obtained by the 2D Beam Propagation Method, and a very good agreement is obtained. The CT is also calculated as a function of the wavelength and the location of the minimum is determined with accuracy better than 2.5 nm at the wavelength of 1550 nm. The developed CMT formulation allows very rapid structure optimization due to the great reduction in the design cycle.

A novel integrated optical modulator design is presented using zero index metamaterial-based Mach-Zehnder Interferometer with photonic crystal phase shifters. The phase modulation relies on the shift between the photonic bandgaps having non-zero and zero effective refractive indices. A small change in the bulk index results in an effective index change between the arms of the MZI due to the disturbance of the band structure. Thus, such a structure provides a new approach for phase modulation on integrated optical systems with the possibility of low insertion losses and lowvoltages.

Plasmonic sensors, leveraging the profound exposure of propagating Surface-Plasmon-Polariton (SPP) modes over metal stripes to test analytes, became so far the “gold-standard” in plasmonic biosensing resulting in commercial available devices. However, a series of challenges associated with their bulky prism-based coupling configuration as well as their high optical losses need to be overcome in order to allow for miniaturized and multiplexed sensor layouts. In this context, selective co-integration of plasmonics with low-loss silicon-nitride photonics emerges as a promising solution towards addressing these challenges yet reaping the benefits from both technologies. In this work, we present an interferometric sensor based on a Mach-Zehnder device, where a “plasmo-photonic” waveguide branch is utilized to interrogate changes in the refractive index of a test analyte exploiting the accumulated phase change of the SPP mode being exposed in an aqueous solution. More specifically, the “plasmo-photonic” Mach-Zehnder sensor incorporates a gold plasmonic stripe with a length of 70 μm and a width of 7 μm that has been interfaced with Si₃N₄ waveguides by means of a butt-coupled interface. By conducting numerical simulations and considering the dispersion properties of the involved materials, we optimized the structural parameters of the sensor aiming at ultra-high bulk sensitivity in the order of micrometres per Refractive Index Unit (RIU).

We present simulation and characterization results for the design of a two-port grating coupler with achievable coupling efficiency up to 54% together with simulation and characterization results of three different multimode interference (MMI) coupler structures, 1x2, 1x4 and 1x8 with insertion loss and output power imbalance as low as 0.2 dB and 0.05 dB, respectively. Both grating coupler and MMI photonic structures were designed on the TriPleX platform. Finally, we present these structures as part of a novel, photonic, ultrasensitive biosensor.

A design of a broadband and high-efficiency SOI grating coupler (GC) for the TE mode is demonstrated. The periodic segments of the GC use Subwavelength Gratings (SWGC), where the width of the silicon segments is much smaller than the operating wavelengths and the width varies along the length of the GC. The SWGC is optimized for TE polarization with a peak CE of–4.5 dB at a wavelength of 1550 nm, with a 1-dB bandwidth of 68 nm ranging from 1521.4 nm to 1589.4 nm and a 3-dB bandwidth of 119 nm from 1497.4 nm to 1616.4nm. The back reflections in the SWGC are suppressed to - 22 dB. The broadband SWGC is integrated with cascaded ring resonators to demultiplex the incoming DWDM signal into individual channels and distribute them into sub-circuits. A layout of the GCs and ring resonators is generated, and systemlevel performance is evaluated.

We propose a fully CMOS compatible optical sensor based on the ring resonator mechanism. The waveguide structure of the sensor utilizes the silicon on insulator slot waveguide configuration. The analyte fills the slot and the cladding of the ring resonator. Since the optical power is enhanced and confined within the slot, then the overlap between the analyte and the optical power is maximized. The sensitivity of the sensor was measured to be 350 nm/RIU at the optical wavelength of 1.55 μm.

Light detection and ranging (LiDAR) systems are potential candidates as sensing systems for autonomous driving. Light sensor performance is highly related to the distance measuring capabilities of the LiDAR system. Silicon photomultipliers (SiPM) have attracted attention because of their capability for detecting even single photons of light. To increase the utilization efficiency of incident light, we thinned the SiPM substrate for light reflectance in the structure to a thickness of 8 μm. This improved photon detection efficiency (PDE) to 1.6 times that of a 700-μm device at an exceeding voltage of 4.0 V above the avalanche breakdown voltage. By reducing diffusion carriers from the substrate, time-lagged signals such as afterpulse or delayed crosstalk were suppressed to 60 %.