This PDF file contains the front matter associated with SPIE Proceedings Volume 12006, including the Title Page, Copyright information, Table of Contents, and Conference Committee listings.

The American Institute for Manufacturing Integrated Photonics (AIM Photonics) runs a silicon photonics multi-project wafer (MPW) program providing riders with access to silicon photonic devices and circuits fabricated in a state-of-the-art 300 mm CMOS line. Current MPW offerings include both silicon and silicon nitride waveguides, GHz modulation/detection, electro-optic switches and filters, low-loss edge coupling, three metal levels, and supports operation in the O, C, and L bands. Often propagation loss is not prioritized for active MPW runs in favor of other key parameters such as modulation speeds, photodiode responsivity, device size, spectral bandwidths, etc. However, for areas such as quantum technology, sensors, LiDAR, and data communications it is an imperative to incorporate both low-loss waveguides and active devices on a single die. These application areas require lower propagation losses because they either use single photons, high Q resonators, and/or require high efficiency coupling for lasers/SOAs. As part of our updated MPW integration, we have demonstrated losses of 1.1 dB/cm in Si strip waveguides and 0.4 dB/cm in SiN strip waveguides, a reduction of 1.4 dB/cm and 1.6 dB/cm, respectively, from our published MPW values.

Silicon photonics is the most promising technology for applications ranging from large-bandwidth, low power consumption datacom transceivers, to wearable health monitoring devices, or optical data-bus for quantum processors. To bring silicon PIC based products to the market, ultra-low loss waveguides would be preferred. In the conventional submicron silicon platforms, higher propagation loss (in the order of ~1 dB/cm) induced by the roughness of the etched sidewalls, as well as higher fiber-to-waveguide coupling loss due to its sub-micron dimensions impose challenges for its deployment in many products. VTT’s thick-SOI technology offers a promising alternative, owing to its lower propagation loss (~0.1 dB/cm), reduced polarization sensitivity, and capacity to handle higher optical power without exciting nonlinear losses. Its micron-scale cross-section enables efficient edge coupling. Exploiting its ultra-low loss, we have demonstrated unprecedented level of integration such as, a 40-channel array waveguide grating (AWG) based mux/de-mux, or a Faraday rotator based on silicon spirals, without employing any magneto-optic material. Now we reduced the propagation loss further, down to record-low 4 dB/m, by controlled annealing of waveguides in 100% pure H2 environment. In our optimized, MPW-compatible annealing process, the atomic mobility of Si smoothens the scallops from etching, without causing any structural deformation of the waveguides. This substantially reduced loss enabled us to develop ultra-high Q ring resonators on our thick-SOI platform, as well as sidewall smoothening for the active components, thereby making our platform a bedrock for the emerging applications such as, quantum computing, biosensors, and 3D imaging.

Optical coupling between fibers and on-chip waveguides is a critical step in photonic testing and packaging. We demonstrated broadband surface-normal fiber-to-chip optical coupling based on free-form micro-optical reflector arrays integrated with foundry-processed SiN photonics. The couplers yield a low fiber-to-waveguide coupling loss of 0.5 dB at 1550 nm wavelength, and an exceptionally broad 1-dB bandwidth encompassing O to L bands (1260 nm to 1640 nm), only limited by the wavelength range of our testing setup. In-plane 1-dB alignment tolerances up to ± 2.4 µm and an out-of-plane 1-dB alignment tolerance up to 20 µm were obtained at 1550 nm. We further show that the Optical Free-Form Couplers for High-density Integrated Photonics (OFFCHIP) platform is universally applicable for chip-to-chip, waveguide to free space, and waveguide to surface-normal device coupling, qualifying it as a universal high-performance optical coupling interface for diverse use scenarios.

Combining Sn alloying and tensile strain to Ge has emerged as the most promising engineering approach to create an efficient Si-compatible lasing medium. The residual compressive strain in GeSn has thus far made the simple geometrical strain amplification technique unsuitable for achieving tensile strained GeSn. Herein, by utilizing two unique techniques, we report the introduction of a uniaxial tensile strain directly into GeSn micro/nanostructures. By converting GeSn from indirect to direct bandgap material via tensile strain, we achieve a 10-fold increase in the light emission intensity.

Grating couplers are one of the building blocks in silicon (Si) photonics. A lithium niobate-on-insulator (LNOI) platform has a wide transparency window, an exceptional electro-optic performance, and a favorable mechanical property. Here we propose a grating coupler on the LNOI platform for an optical fiber to an ultra-low-loss silicon nitride (Si₃N₄) waveguide. Titanium dioxide (TiO₂) has a negative thermo-optic coefficient and can be used to compensate the temperature drift of cores with positive thermo-optic coefficients. Here, a TiO₂ layer on the high-aspect-ratio Si₃N₄ core is used for the athermal operation. The fundamental TE mode at a wavelength of 1550 nm is used as an input from the ultra-low-loss waveguide. We achieve a high directionality of 68% at the fixed wavelength. A coupling efficiency of 48% can be obtained. A 3-dB bandwidth of 60 nm from 1520 to 1580 nm is presented by the proposed grating coupler.

Silicon photonics has become the key enabling technology in many sensor applications including light detection and ranging (LiDAR) systems because of its high integration, chip-scale footprint and CMOS-compatible process. Thanks to these advantages, optical phased array (OPA) based on silicon photonics has emerged as a solid-state LiDAR solution to replace mechanical LiDAR counterpart. In such a system, optical loss from each component of the OPA devices should be minimized, while the radiation efficiency from the radiators of the OPA devices should be maximized for extending the power budget of the LiDAR system. These components can improve their performances through the recently emerged inverse design method. In this study, we designed a novel grating structure which is one of the components of OPA and allows wide-band and high coupling efficiency of light using inverse design approach with the particle-swarm-optimization method. Considering Silicon-On-Insulator (SOI) platform with 220 nm thickness, the configuration of the grating structure is determined by the finite number of particles so that the height and width of the corrugations are optimized based on the objective of boosting the out-of-plane radiated power amount. Highly efficient and vertical emission was obtained using finite-difference-time-domain calculation in telecommunication window centered at around 1550 nm. Including additional constraints in the inverse design will allow the realization of multitude spatial field profiles of the radiated light that may have an important contribution for OPA, sensing, imaging, lasers and optical interconnection.

The performance of the current-assisted single-photon avalanche diode (CA-SPAD) can be demonstrated to its full extent when used in conjunction with an active quenching circuit (AQC) located on the same chip. Counting rates, photon detection probability and single-photon timing resolution improve substantially as is evidenced by measurements in this paper. It is also demonstrated that a PDP of 20 % at 940 nm can be reached, making the CA-SPAD one of the best performing front-side illuminated (FSI) CMOS SPADs for near-infrared (NIR) operation.

One of the challenges of mid-wave infrared (MWIR) silicon (Si) photonics is related to the low absorption of Si-based photodetector focal plane arrays (FPAs), and therefore the reduced quantum yield. Another challenge is related to the significant thermal noise in uncooled FPAs which spoils the quality of imaging. It is proposed that the technology of Si anisotropic wet etching, capable of fabricating light concentrating arrays, can be used for solving these problems. The proposed designs are based on monolithic integration of Si micropyramids with metal/silicide Schottky barrier photodiodes (SBD). By using finite-difference time-domain (FDTD) modeling, it is shown that the photons can be spatially concentrated and resonantly trapped near the tips of the pyramids, allowing for multiple passes in the silicide layer and thus increasing the likeliness of photon absorption. This potentially leads to multispectral imaging functionality at the resonant frequencies. In addition, these resonances can be excited in a broad range of angles leading to MWIR FPAs with a wide angle-of-view. To demonstrate the proposed concept, micropyramidal arrays with three different geometrical parameters were fabricated and integrated with nickel/silicide (NiSi) SBDs. The choice of Ni was determined by the simplicity of short-wave IR (SWIR) testing at room temperature, but in the future, similar studies can be performed in the MWIR range by using Au or Pt. Preliminary testing results revealed a stronger photoresponse from micropyramids with smaller tops, but further studies are required to compare the performance of such novel photodetector arrays with an extensive range of geometrical parameters.

Owing to their direct band gaps, (Si)GeSn all-group-IV alloys are promising candidates for light sources, photodetectors and modulators monolithically integrated onto a CMOS-compatible mid-infrared photonic platform. Several research teams have demonstrated optically pumped GeSn lasers, and, more recently, an electrically pumped GeSn laser at low operating temperature. Here, we studied Ge_0.85Sn_0.15-based light emitting diodes (LEDs) and photodiodes (PDs) operating at room temperature. The stack was grown on a p-doped Ge strain-relaxed buffer at low growth temperatures (below 350°C) in a 200 mm chemical vapor deposition tool. Fabricated GeSn devices were characterized at room temperature with a Fourier-transform infrared spectrometer (FTIR) and an InSb detector. The spectral response of the FTIR InSb detector was calibrated with respect to a Deuterated Triglycine Sulfate detector (DTGS). This spectral response was then used to correct Ge_0.85Sn_0.15 LEDs emission spectra with emission maximum at 3.3 μm. The cutoff wavelength at 3.7 μm of the GeSn photodiode was finally obtained (at 0V bias) after correction of the Globar incident light spectrum. Such emission and detection open up promising perspectives for all-group-IV LEDs and PDs in applications such as gas sensing.

In this paper, we present the tauCAM, a compact sub-nanosecond time-gated video framerate imaging camera, with our new 64×64-pixel Current-Assisted Photonic Sampler (CAPS) sensor. It features gating widths of less than 1 ns with a jitter of less than 60 ps rms on the gating width and less than 50 ps rms on the position. It has a quantum efficiency (QE) of more than 40% for near-infrared wavelengths. It’s peak QE is 61% at 675 nm. The sensor is fabricated in a conventional 350 nm CMOS process.

We give an overview of the design of the new camera hardware, with characterization of the timing circuitry and gating signals. Furthermore, the new sensor is discussed in detail. The revised pixel design yields improvements in QE, with high QE even for very short gating windows. Additionally, the Instrument Response Function of the pixel is characterized.

The capabilities of the tauCAM are demonstrated in an experimental setup where we image a scene that is sequentially illuminated with red, green and blue light, on a nanosecond time scale. Due to its fast-gating mechanism, our CAPS sensor can distinguish and image these colors separately, while the human eye merely sees white illumination.

Integrated photonic systems require reliable, low power consumption phase shifters in order to scale circuit complexity. Micro-electromechanical systems (MEMS) are a viable candidate to provide low-power phase shifting, without the significant drawbacks of thermo-optic effects (high power usage and cross-talk). Previous works have demonstrated MEMS phase tuning through vertically displaced microbridges. However, these require > 40 V for a π phase shift [1] using gradient electric fields, though lower voltage requirements have been demonstrated for direct electrostatic actuation [2]. Ultra-low voltage (∼ 1 V) designs using horizontal slot waveguides have recently been demonstrated [3–5] although these methods require complex mechanical structures that must be released using vapor-HF or critical point drying post-processing. Here we present low-voltage phase tuning of vertically actuated beams that are released at wafer level with a vapor XeF₂ etch completely in-house. Our process is carried out on an i-line photolithography stepper to define the waveguiding, metal, and MEMS structures. We use a sacrificial polysilicon layer between the SiN waveguide and the SiN beam. The XeF₂ undercuts the beam, enabling a simple MEMS release process that does not undercut the waveguide. The movable SiN beam on top of the waveguide utilizes a single-sided anchor so that it resembles a wide and short single-clamped cantilever. This enables a phase shifter that is capable of a π phase shift with < 10 V and length < 100 μm. We measure the optical transmission versus applied voltage for multiple voltage sweeps and extract the phase shift per voltage at various wavelengths. We demonstrate reliable tuning over multiple sweeps with an average voltage of 7 V ± 0.5 V for a π phase shift. This phase shifter is central to the scalability of programmable photonic circuits, including quantum photonics.

The last few years have shown the success of silicon nitride platforms for ultra-low loss tightly confining waveguides. In addition to the low optical losses, the high Kerr nonlinearity, the high power handling capability and small bending radii makes the platform ideal for nonlinear photonics. Therefore, the potential for applications is huge: LiDAR, microwave optics, quantum photonics, neuromorphic computing, telecommunication, sensors… Here, we present our 200mm platform based on 800nm-thick LPCVD Si3N4 with optical losses below 5dB/m. It is completed with a set of photonic components: grating couplers, edge couplers, MMI, directional couplers, Y-junction and AWG multiplexer, which constitute the building blocks for advanced applications.

We present work towards a visible wavelength tuneable external cavity laser (ECL) on a silicon nitride platform working around 640 nm. A ring resonator Vernier structure on the photonic integrated circuit (PIC) provides delayed feedback with spectral filtering and tuning. Gain is provided by a reflective semiconductor optical amplifier (SOA) grown on a GaAs substrate and integrated by pick-and-place flip-chip assembly. In a novel coupling scheme, the 1-dB in-plane placement tolerance is relaxed by a multi-mode edge-coupler to ± 2.6 µm in the direction parallel to the SOA edge and to displacements up to 3.5 µm from the PIC interface along the SOA’s optical axis. Pedestals defined in the PIC guarantee vertical alignment.

The advent of the SARS-CoV-2 pandemic has rekindled the demand for inexpensive, point-of-care and at-home diagnostic systems that offer high degrees of scalability, sensitivity, and specificity. While several options of sensing modalities have been researched and subsequently commercialized, these sensing systems are yet to simultaneously satisfy the spiked demand for higher accuracy and scalable manufacturing. In this context, the prospect of integrated photonics-enabled biosensors has garnered immense attention from both scientific and business communities. However, realizing low group indices of the photonic structures required for higher bulk sensitivities at commonly used telecom operation wavelengths is typically achieved using design approaches incompatible with foundry process constraints. Siphox Inc., founded in 2020, developed an ensemble biosensing platform by merging the benefits of CMOS-friendly integrated photonic structures with proprietary biochemical assays to realize low-cost, highly sensitive, label and label-free, multiplexed diagnostic system. As a first demonstration, we present our results of 15-plex biosensing utilizing low-loss (<3.5dB/cm) Si₃N₄ strip-waveguide ring resonators fabricated using 248 nm deep UV (DUV) stepper lithography. We describe the design, simulation, and measurement results of bulk and surface sensitivities and detection limits for our TE-polarized waveguide resonator structures operating at O-band (1310 nm). We demonstrate a bulk sensitivity of >117 nm/RIU and an intrinsic limit of detection of 1.87×10⁻⁴ RIU.

We present a new approach for the modelling of non-linear effects in silicon based ring resonators by coupling equations for Two-Photon-Absorption (TPA), Free-Carrier-Absortpion (FCA) and self-heating with the Shockley–Read–Hall theory involving trap-assisted recombination processes. SRH gives a non-linear carrier lifetime which is essential to fit model results with the experiments. The developed model is validated by comparison with experimental measurements performed on different ring types and it is employed in the design of rings with minimal non-linear effects for integration in ring-based Si PIC mirrors for high power hybrid III-V/Si tunable lasers.

In this paper, we demonstrate a high-efficiency, short-cavity heterogeneously integrated C-band DFB laser on a Si waveguide realized using adhesive bonding. First, simulation results regarding the integrated cavity design are discussed. In order to decrease the optical loss inside the cavity, we designed a configuration where the optical mode inside the laser cavity is predominantly confined to the Si waveguide underneath. Then, the fabrication technology of the demonstrated device is explained. Finally, we discuss the measured static and dynamic characteristics of the integrated laser. Up to 13% wall plug efficiency is achieved for a 200 μm long DFB laser diode at 20 ⁰C. Up to two times 6 mW of optical power is coupled into the silicon waveguide and more than 44 dB side-mode suppression ratio is obtained. In addition, the dynamic characteristics of the device are demonstrated by non-return-to-zero on-off keying modulation at 20 Gb/s and the transmission over a 2 km long optical fiber.

A novel process design kit (PDK) offering providing seamless access to the Albany NanoTech Complex’s 300mm foundry with a mission to promote silicon photonics technology is demonstrated. Unlike traditional pure-play foundries, we have developed a framework that allows our PDKs to contain libraries developed by internal and external domain experts. In addition to integrated Electronic Photonic Design Automation (EPDA) platforms, our PDK is also released in an alternate PIC design flow that the lowers the cost barrier for organizations. Further, our PDKs target a broad application space that includes telecom as well emerging areas such as sensors and quantum photonics – all with the ability for onboard light sources. A PDK from American Institute of Manufacturing (AIM Photonics) will be discussed that demonstrates these features.

In this work, we demonstrate a unique structured carrier injection silicon photonics micro-ring modulator that exhibits a large extinction ratio and a high modulation efficiency. The modulator consists of a ring and a double-bus straight waveguide. The ring has a radius of 7 µm and a 220-nm silicon-on-insulator (SOI) waveguide is used both for the ring and the straight waveguides. The waveguide has a width of 450 nm and a slab thickness of 110 nm with a full silicon height (220 nm) for the contact area. The slab width is 1 µm on both sides from the 450-nm core width and the contact full silicon width is 1.75 µm. The rib ring and the bus waveguides are separated by a gap of 100 nm. The modulator has three doping levels with concentrations of 1018, 1019, and 1020 cm-3 for the core, slab, and the contact areas, respectively. The device is fabricated using the American Institute for Manufacturing Integrated Photonics (AIM Photonics) Multi-Project Wafer (MPW) service. It is tested with a tunable light source that has wavelengths ranging from 1485 nm to 1590 nm. The light is coupled to the modulator using grating couplers. The measured free spectral range of the ring resonator is about 13 nm. The fabricated ring modulator exhibits a large extinction ratio of 21 dB and a high modulation efficiency of 3.7 nm at a direct current (DC) voltage of 1.5 V.

We present a suspended SiGeSn microring laser design that enables strain relaxation of the material layer stack, electrical pumping and adequate heat sinking. Using both strain and composition as two degrees of freedom to engineer the band structure, a direct bandgap is obtained in the gain material of a double heterostructure layer stack, and the L- to Γ-valley energy difference increased to 78 meV, by 66% compared to a non-underetched structure. The temperature dependent current threshold is modeled for the designed device and determined to be 18 kA/cm² at 50 K. The fabrication process is outlined and first experimental electroluminescence results indicating the effectiveness of our approach are reported. At the time this proceedings paper is being submitted, electrically pumped lasing has also been achieved with a similar structure, with results that will be reported in a future publication.

GeSn alloys have emerged as a promising material for realizing CMOS-compatible light sources. GeSn lasers demonstrated to date have large device footprints and active areas, which limit the realization of densely integrated lasers operating at low power consumption. Thanks to their intrinsically small device form factors, 1D photonic crystal lasers may offer opportunities to overcome such limitations of large GeSn lasers. Here, we present a 1D photonic crystal nanobeam laser with a very small device footprint (~7 μm²) and a compact active area (~1.2 μm²) on a GeSn-on-insulator substrate.

In the quest for practical group IV lasers, researchers have proposed a few ideas such as strain engineering of Ge and alloying of Sn into Ge. Both approaches fundamentally alter bandstructure such that Ge can become a direct bandgap material. Recently, relaxation of limiting compressive strain and addition of mechanical tensile strain have been employed to improve the lasing performance. However, such strain engineering has thus far been possible only in suspended device configurations, which significantly limit heat dissipation and hinder the device performance. We herein demonstrate GeSn microdisk lasers fully released on Si that relax the limiting compressive strain and achieve excellent thermal conduction.

This paper proposes the design an all-optical 1-bit digital comparator. The comparator structure consists of micro-ring resonators (MRR) paired with a constant light source (COS). MRRs in the comparator design are utilized as modulators by tuning their resonant wavelengths. In this way, under no external disturbances, the rings are uncoupled by default. The proposed 1-bit digital comparator is CMOS-compatible meaning that it can be fabricated using the existing technologies. Also, to reduce the fabrication complexity of the proposed device, thermo-optic modulation is employed as the primary light modulating technique. The 1-bit digital comparator is tested at 0.5 Mbps. The study concludes with suggestions on design improvements and potential application in photonic computing.

We demonstrate two-dimensional (2-D) beam-steering using only wavelength control from one-dimensional siliconbased OPA, where path differences are sequentially formed in each channel. With 79.6-μm path difference in phasefeeding lines and a 2-μm pitch in grating radiators, we achieved a continuous transversal steering about 46° and a longitudinal steering near 13° with a wavelength tuning of 90 nm. The single-beam with divergence angle of 4° was formed by phase initialization using electro-optic optic p-i-n phase shifters before beam-steering.

In this paper, we design and demonstrate the optical encoder circuit. This device performs the function of encoding a 4- bit electrical signal into a 2-bit optical signal. The encoder structure is based on micro-ring resonator (MRRs) structures. A constant light (COS) is applied into an input port of the circuit, and depending on the electrical signals fed to heaters in MRRs; the input light is directed to different output ports. The performance of the proposed encoder is verified with the static and dynamic responses. The dynamic response of the encoder is tested up to 500Kbps. The proposed encoder is CMOS-compatible and can be manufactured using existing technologies that can be used for photonics computing and control.

We proposed a compact and longitudinally zig-zag shaped 1x4 power splitter using particle swarm optimization algorithm integrated with the finite-difference time-domain method. Different particle sizes in the algorithm are tested and splitter structures with high uniformity (less than 0.04 dB) and small insertion loss (less than 0.40 dB) are achieved over a wide bandwidth. Our designs show the best performance with low insertion loss and high uniformity comparing to the existing ones, while it can be fabricated with industry-standard lithography due to its unit cell length of 100 nm or more.

In this work we reported a photonic thermal light emitter based on double coincide rings-patterned photonic crystal structure of highly-doped silicon coated with platinum. The structure periodicity is 2 μm and the rest of design dimensions were tuned to achieve either a wideband or multi-band wavelength range in the near and mid-infrared spectral ranges. Finite difference time domain analysis showed that a wide spectral range with a 3-dB spectral width of 3.7 μm around 2.5 μm central wavelength or dual-band operation with 3-dB spectral widths of 2.5 μm and 3 around 1.5 and 7 μm central wavelengths, respectively could be achieved.