Silicon-nitride-based photonic integrated circuits (PICs) can operate with low loss at visible and near-infrared wavelengths. This spectral range is essential for many applications in chemical and biological sensing, quantum sensing and networking, physical sensing, precision timekeeping, and augmented/virtual reality. At present, highquality silicon nitride PIC platforms optimized for operation in the visible are offered by low-volume custom foundries or by 200 mm silicon-based foundries. Both typically lack the minimum feature sizes and wafer throughput required for high-yield, high-volume operation at short wavelengths. In this work we describe a new component library and foundry process developed at AIM Photonics, a state-of-the-art PIC foundry. The TLX-VIS component library for the Silicon Nitride Passive PIC process is designed to operate in three bands at wavelengths from 500 nm to 1000 nm. A trench down to the primary waveguide layer is offered for sensing applications, and a dicing trench enables access to waveguide facets for low loss edge coupling. Propagation losses range from 0.2 dB/cm at 785 nm to 2 dB/cm at 532 nm. The component library is designed for both the TE00 and TM00 modes and includes broadband directional couplers, polarization rotators, edge and grating couplers, lattice filters, and high-Q ring resonators. The waveguides have small minimum bend radii (<100 μm) and low fluorescence, which is critical for applications in Raman sensing and quantum information. The component library and PICs are compatible with AIM Photonics’ Test, Assembly, and Packaging facility, enabling fully-packaged, fiber-attached assemblies.
As silicon photonics-based circuit designs transition from lab to fab, an end-to-end automated measurement flow is required to address a unique combination of high flexibility in test conditions and high volume. This paper describes such a flow for process design kit (PDK) development in the state-of-the-art 300 mm CMOS-compatible silicon photonics foundry at the Albany NanoTech Complex in Albany, NY. Presenting details of this measurement flow will offer considerable cost and time savings to new users in this area. The measurement flow begins at the layout stage, where users can instantiate various combinations of pre-characterized padsets that contain DC/RF pads and optical couplers, which are compatible with the automated electro-optic setup used for measurements. These padsets are offered via two options: (1) a script-based layout builder tool or (2) a parametric cell in a “Measurement Design Kit” offering in a design automation platform, which is an analog to a PDK. Special marker layers are added to the padsets, whose coordinates are extracted after the layout is complete. The coordinates are then passed to fiber positioners on the semi-automated prober while performing measurements. Electro-optic measurements are performed across the wafer using vertical coupling, which is well-suited for large-scale measurements. The wafer is placed on a 300 mm prober with automated fiber positioners that can optimize optical coupling across six degrees of freedom. The electro-optic measurement setup is based on the Keysight Photonic Application Suite. It includes a tunable laser, polarization synthesizer, and multi-channel detectors that measure transmission in both TE and TM polarizations. A lowloss optical switch matrix is programmed to switch connections between lasers and detectors to 16 grating couplers in the padset. The entire measurement setup, including the prober and instruments, is driven using the Python-based SweepMe! automation framework, which is modular and allows for the easy creation of test plans.
We demonstrate a vertical-junction, carrier-injection, micro-ring modulator that is fabricated using AIM Photonics’ 300 mm Quantum FLEX Platform which shows results with high modulation efficiency and a large ON-OFF ratio. The modulator device includes a ring and a single-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 with a rib structure of 110-nm slab thickness. The width of the core waveguide is 550 nm for both the ring and the straight waveguides. The slab width between the full-height silicon core and contact area is kept at 1 μm on both sides from the 550-nm core. The coupling gap between the ring and the bus waveguide is designed to be 150 nm. To make the waveguide core vertical junction, the upper half of the core is n-doped and the lower half is p-doped. To have a smooth electrical connectivity between the core and the contact area, three-level doping is applied where the core is doped with the minimum concentration and the contact silicon area is doped with the highest concentration. The modulator is tested with a tunable laser over a 100-nm window extending from 1485 nm to 1585 nm. The light is coupled to the modulator using grating couplers which are used to couple input and output light. The vertical junction shows excellent direct current (DC) I-V characteristics and the modulator performs at high modulation efficiency of about 1.14 nm and a large ON-OFF ratio of about 21 dB at 1.0 V.
In this work, we demonstrate a cascaded ring resonator based wide stop-band filter. The filter consists of four cascaded rings and a bus waveguide. The first ring has a radius of 7μm, the second, third and the fourth rings have radius of 7.01 μm, 7.02 μm, and 7.03 μm, respectively. The radius varion is designed for a small shift of resonant wavelength so that the combined resonance effect of four ring resonators exhibits a wide stop-band filter function compare to a single ring resonator. Both the bus and ring waveguides have a width of 480 nm. The thickness of the waveguides were 220 nm which is a standard silicon-on-insulator (SOI) wafer available in the market. A 100-nm gap is designed between the ring and the bus waveguide to provide optimum filtering. The device is fabricated using the American Institute for Manufacturing integrated Photonics (AIM Photonics) 300mm Multi-Project Wafer (MPW) service. It is tested using the AIM Photonics inline vertical grating coupled automated measurement tool with a tunable light source that has wavelengths ranging from 1485 nm to 1590 nm and a wavelength resolution of 60 pm. The fabricated cascaded ring filter exhibits a 3-dB stop-band about 6 nm wide with an extinction ratio of ~30 dB in across the S, C and L-bands. It is noted that the desired width of the stop-band is achievable by cascading required number of rings with slight radius variation.
In this work we explain the methodology and techniques for building an end-to-end design enablement (DE) platform from component design to process design kit (PDK) release for silicon photonics-based photonic integrated circuit (PIC) design. Elements of the DE include: component design, layout and test site development, measurement infrastructure and PDK development. Our methodology builds on the best practices followed in CMOS and RF foundries but adds unique features specific to silicon photonics. The DE flow is developed on the American Institute for Manufacturing Integrated Photonics’ (AIM Photonics) 300 mm silicon photonic technologies manufactured in a limited-volume foundry at the Albany Nanotech Complex, in Albany, NY. For component development, the AIM Photonics PDK offers a process stack file supported in Lumerical platform that applies linewidth corrections and doping information to imported layouts increasing the efficiency and accuracy of the design. For test sites, an automated layout and connectivity framework is explained that allows users to generate a layout from spreadsheet inputs that is also compatible with automated waferscale measurements. AIM Photonics PDKs include layout, models and design-rule-check (DRC) tools that are offered across multiple platforms. The DRC decks are offered in commercial tools such as Cadence and Synopsys, as well as KLayout. We present features of layouts and communication with schematics. In addition, we also explain techniques for processing and analyzing measured statistical data and extracting platform specific compact models. Presenting this methodology to the wider community is integral to the mission of AIM Photonics and will be of immense benefit particularly to small organizations engaged in prototype development.
In this work, we demonstrate a compact pn junction ring modulator with very large extinction ratio and high quality factor. The modulator consists of a 5-μm radius ring and a single-bus straight waveguide. Both the ring and straight waveguides have a width of 480 nm and heigh of 220 nm. The waveguides are rib-structured and the rib thickness is 110 nm with a slab thickness of 110 nm from a 300mm wafer with 220-nm silicon-on-insulator (SOI) thickness. A 100-nm gap is designed between the rib ring and the bus waveguides. The modulator has three nominal 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 using the AIM Photonics inline vertical gratting coupled automated tool with a tunable light source that has wavelengths ranging from 1485 nm to 1590 nm and a wavelength resolution of 60 pm. The fabricated 5-μm radius ring modulator exhibits high quality output with a very large extinction ratio of 29 dB over a broad wavelength spectrum of about 100 nm. The device has a very wide free spectral range (FSR) of about 19 nm.
The reduction of optical loss for integrated photonics I/O is an important area of active research. Edge coupling (end-firing) is a key I/O technology, having advantages over grating couplers in terms of spectral bandwidth and lower insertion loss1. Low-loss edge coupling into silicon waveguides will be critical to datacenters and telecommunications systems in order to help accommodate the aggressive growth of data analytics applications2. In this work, we investigate the coupling losses from optical fiber (SMF-28) into on-chip silicon waveguides using silicon nitride edge couplers with varying chip facet angles. The expected losses were simulated using Three Dimensional Finite-Difference Time-Domain (3D-FDTD) modelling and measured experimentally to close the design-fabrication loop. The chips were produced within a state-of-the-art 300 mm CMOS foundry, using edge couplers from the foundry Process Design Kit (PDK). During optimization of the photolithography and dry etching process, the facet angle deviation from 90° was minimized. Insertion loss of the SiN edge coupler was investigated via transmission measurements utilizing both cleaved fibers and fiber V-grooves. Facet angles varied from approximately 75°–90° were tested for insertion loss and trends were consistent with the 3D-FDTD modelling. Measurements were performed over a range of 1450–1650 nm using a tunable laser source and optical power meter. In addition, facet insertion loss was isolated by using propagation loss data from an in-line testing tool that measured silicon waveguides propagation losses, on wafer and in the same wavelength band.
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.
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.
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.
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.
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.
Silicon photonics is becoming a significant platform in high-bandwidth, low power device applications for HPC and cloud computing infrastructure. Its continuing push to displace incumbent copper and VCSEL technologies depends on the scaling potential of existing CMOS manufacturing processes. Central to this process is still the photomask, and its’ ability to accurately render design intent. However, processes and quality metrics that have been developed for electronics-centric photomasks do not translate directly to the needs of photonics-centric photomasks. This may lead to unconventional or non-intuitive choices for data rendering (fracture), mask pattern tooling (laser vs e-beam). Standard metrology (CD Uniformity, Localized LER) may not capture the essential elements that correlate mask pattern fidelity with waveguide signal loss. There are likely limits to a “blind translation” of IC-centric metrics to photonics-centric metrics. This paper will report on a collaborative effort to compare several photomask manufacturing approaches and their impact on photonics device performance (signal loss) for a common set of device structures. We will also explore the standard metrics applied to photomask quality and determine whether they correlate to waveguide performance, or whether different metrology approaches are required for vetting photonics-centric photomasks.
Continual development of optical testing methodologies for silicon photonic components and circuitry is instrumental for the overall growth of the field. A mature scheme capable of coupling light between the fiber core and single mode silicon-on-insulator (SOI) waveguides for wafer-scale testing are grating couplers. When silicon photonics are integrated into 3D architectures, the photonics layer may undergo multiple wafer flipping steps through bond/de-bond modules. Architectures such as this require optical testing on the front and backside of the wafer. Conventional grating couplers integrate reflective layers or additional layers of gratings to increase coupling efficiency. These techniques however will not work in both wafer orientations. In addition, including separate test structures for both front and backside fabrication increases device footprint and drives up manufacturing costs. We present an isotropic grating coupler that provides moderate coupling efficiency for both front and backside wafer-scale testing. The grating coupler has been designed for use in the AIM Photonics multi project wafer (MPW) platform, thus enabling non-contact optical interfacing irrespective of the wafer orientation. We have numerically demonstrated coupling efficiencies of 34% (-4.7dB) and 28% (-5.5 dB) for the wafer front and backside respectively while operating at a wavelength of 1550 nm. With proof of concept established, we foresee an eventual pathway for achieving higher efficiency isotropic grating couplers traversing into more 3D silicon photonic architectures.
Nanotechnology has recently been applied to a wide range of biological systems. In particular, there is a current push to
examine the interface between the biological world and micro/nano-scale systems. Our research in this field has led to
the development of novel strategies for spatial patterning of biomolecules, electrical and optical biosensing,
nanomaterial delivery systems, single-cell manipulation, and the study of cellular interactions with nano-structured
surfaces. Current work on these topics will be presented, including work on novel, semiconductor-based DNA detection
methods and mechanical, atomic force microscopy (AFM)-based characterization of bacterial biofilms in threedimensional
microfluidic systems.
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