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.
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