Silicon nitride-on-silicon bi-layer grating couplers were designed for the O-band using an optimization-based procedure that accounted for design rules and fabricated on a 200 mm wafer. The designs ...were sufficiently robust to fabrication variations to function well across the wafer. A peak fiber-to-chip coupling efficiency to standard single mode fiber of -2.2 dB and a 1-dB bandwidth of 72.9 nm was achieved in the representative device. Over several chips across the wafer, we measured a median peak coupling efficiency of -2.1 dB and median 1-dB bandwidth of 70.8 nm. The measurements had good correspondence with simulation.
Abstract
Visible and near-infrared spectrum photonic integrated circuits are quickly becoming a key technology to address the scaling challenges in quantum information and biosensing. Thus far, ...integrated photonic platforms in this spectral range have lacked integrated photodetectors. Here, we report silicon nitride-on-silicon waveguide photodetectors that are monolithically integrated in a visible light photonic platform on silicon. Owing to a leaky-wave silicon nitride-on-silicon design, the devices achieved a high external quantum efficiency of >60% across a record wavelength span from
λ
~ 400 nm to ~640 nm, an opto-electronic bandwidth up to 9 GHz, and an avalanche gain-bandwidth product up to 173 ± 30 GHz. As an example, a photodetector was integrated with a wavelength-tunable microring in a single chip for on-chip power monitoring.
In this paper, we review and provide additional details about our progress on multilayer silicon nitride (SiN)-on-silicon (Si) integrated photonic platforms. In these platforms, one or more SiN ...waveguide layers are monolithically integrated onto a Si photonic layer. This paper focuses on the development of three-layer platforms for the O- and SCL-bands for very large-scale photonic integrated circuits requiring hundreds or thousands of waveguide crossings. Low-loss interlayer transitions and ultralow-loss waveguide crossings have been demonstrated, along with bilevel and trilevel grating couplers for fiber-to-chip coupling. The SiN and Si passive devices have been monolithically integrated with high-efficiency optical modulators, photodetectors, and thermal tuners in a single photonic platform.
Laser beam scanning is central to many applications, including displays, microscopy, three-dimensional mapping, and quantum information. Reducing the scanners to microchip form factors has spurred ...the development of very-large-scale photonic integrated circuits of optical phased arrays and focal plane switched arrays. An outstanding challenge remains to simultaneously achieve a compact footprint, broad wavelength operation, and low power consumption. Here, we introduce a laser beam scanner that meets these requirements. Using microcantilevers embedded with silicon nitride nanophotonic circuitry, we demonstrate broadband, one- and two-dimensional steering of light with wavelengths from 410 nm to 700 nm. The microcantilevers have ultracompact ~0.1 mm
areas, consume ~31 to 46 mW of power, are simple to control, and emit a single light beam. The microcantilevers are monolithically integrated in an active photonic platform on 200-mm silicon wafers. The microcantilever-integrated photonic circuits miniaturize and simplify light projectors to enable versatile, power-efficient, and broadband laser scanner microchips.
Low-loss broadband fiber-to-chip coupling is currently challenging for visible-light photonic-integrated circuits (PICs) that need both high confinement waveguides for high-density integration and a ...minimum feature size above foundry lithographical limit. Here, we demonstrate bi-layer silicon nitride (SiN) edge couplers that have ≤ 4 dB/facet coupling loss with the Nufern S405-XP fiber over a broad optical wavelength range from 445 to 640 nm. The design uses a thin layer of SiN to expand the mode at the facet and adiabatically transfers the input light into a high-confinement single-mode waveguide (150-nm thick) for routing, while keeping the minimum nominal lithographic feature size at 150 nm. The achieved fiber-to-chip coupling loss is about 3 to 5 dB lower than that of single-layer designs with the same waveguide confinement and minimum feature size limitation.
Automatic resonance alignment tuning is performed in high-order series coupled microring filters using a feedback system. By inputting only a reference wavelength, the filter transmission is ...maximized on resonance, passband ripples are dramatically reduced, and the passband becomes centered at the reference. The method is tested on fifth-order microring filters fabricated in a standard silicon photonics foundry process. Repeatable tuning is demonstrated for filters on multiple dies from the wafer and for arbitrary reference wavelengths within the free spectral range of the microrings.
A polarization-independent grating coupler is proposed and demonstrated in a 3-layer silicon nitride-on-silicon photonic platform. Polarization independent coupling was made possible by the ...supermodes and added degrees of geometric freedom unique to the 3-layer photonic platform. The grating was designed via optimization algorithms, and the simulated peak coupling efficiency was -2.1 dB with a 1 dB polarization dependent loss (PDL) bandwidth of 69 nm. The fabricated grating couplers had a peak coupling efficiency of -4.8 dB with 1 dB PDL bandwidth of over 100 nm.
We demonstrate matched pairs of multi-ring Vernier filters that mutually suppress the out-of-band resonances resulting from the Vernier effect to increase the free-spectral range (FSR) while ...achieving high out-of-band extinction ratio. These filters can be aligned to any center wavelength within the Vernier FSR. Both the design methodology and alignment procedure rely on derivative-free optimization methods. We report on an O-band silicon microring optical filter achieving out-of-band extinction of −52 dB over an FSR <inline-formula><tex-math notation="LaTeX">></tex-math></inline-formula>100 nm.
We demonstrate foundry-fabricated O-band III-V-on-silicon discrete-mode lasers. The laser fabrication follows the back-side-on-buried-oxide laser integration process and is compatible with complex, ...multilayer, silicon-on-insulator based platforms. A series of devices were characterized, with the best devices producing on-chip powers of nearly 20 mW with Lorentzian linewidths below 20 kHz and a side mode suppression ratio of at least 60 dB.
We introduce a new III-V-on-Silicon (Si) heterogeneous integration platform, where the III-V material is bonded to the back of a processed Si photonic wafer. This "Back-Side-on-Buried Oxide" (BSoBOX) ...process is fully compatible with active, multilayer Si photonics platforms. This article describes the process flow and reports on O-band hybrid distributed feedback (DFB) lasers of various grating periods fabricated on this platform. A comprehensive set of measurements show that the quarter-wave shifted DFB lasers have comparable performance to front-side platforms. Single-mode emission with a side mode suppression ratio around 50 dB was measured between 20 <inline-formula><tex-math notation="LaTeX">^\circ</tex-math></inline-formula>C - 60 <inline-formula><tex-math notation="LaTeX">^\circ</tex-math></inline-formula>C. The DFB lasers had threshold currents as low as 32 mA and produced output powers in the Si waveguide from a single-end of about 15 mW at 170 mA before the devices began to mode hop. Output powers of <inline-formula><tex-math notation="LaTeX">\sim</tex-math></inline-formula>20 mW were measured before the onset of thermal roll-off and operation up to 80 <inline-formula><tex-math notation="LaTeX">^\circ</tex-math></inline-formula>C was achieved. The characteristic temperatures and thermal impedance of the lasers were evaluated and future improvements are discussed.
PDF
