III-V-on-silicon 2-µm-wavelength-range wavelength demultiplexers with heterogeneously integrated InP-based type-II photodetectors

High-speed and high-responsivity p-i-n waveguide photodetector at a 2 µm wavelength with a Ge0.92Sn0.08/Ge multiple-quantum-well active layer

We report on p-i-n waveguide photodetectors with a ${{\rm Ge}_{0.92}}{{\rm Sn}_{0.08}}/{\rm Ge}$ multiple-quantum-well (MQW) active layer on a strain-relaxed Ge-buffered silicon substrate. The waveguide-photodetector structure is used to elongate the photo-absorption path and keeps a short photo-generated carrier transmission path. In addition, the double-mesa structure with a low substrate doping concentration is implemented, which minimizes the parasitic capacitance. As a result, a high responsivity of 119 mA/W at ${-}{1}\;{\rm V}$ and a high bandwidth of more than 10 GHz at ${-}{7}\;{\rm V}$ were achieved at a 2 µm wavelength. Compared with the surface-illuminated photodetector, the responsivity was improved by ${\sim}{8}$ times at a 2 µm wavelength, while keeping the comparable bandwidth.

Design and Simulation Investigation of Si3N4 Photonics Circuits for Wideband On-Chip Optical Gas Sensing around 2 µm Optical Wavelength

We theoretically explore the potential of Si₃N₄ on SiO₂ waveguide platform toward a wideband spectroscopic detection around the optical wavelength of 2 μm. The design of Si₃N₄ on SiO₂ waveguide architectures consisting of a Si₃N₄ slot waveguide for a wideband on-chip spectroscopic sensing around 2 μm, and a Si₃N₄ multi-mode interferometer (MMI)-based coupler for light coupling from classical strip waveguide into the identified Si₃N₄ slot waveguides over a wide spectral range are investigated. We found that a Si₃N₄ on SiO₂ slot waveguide structure can be designed for using as optical interaction part over a spectral range of interest, and the MMI structure can be used to enable broadband optical coupling from a strip to the slot waveguide for wideband multi-gas on-chip spectroscopic sensing. Reasons for the operating spectral range of the system are discussed.

High-speed photo detection at two-micron-wavelength: technology enablement by GeSn/Ge multiple-quantum-well photodiode on 300 mm Si substrate

We report high-speed photo detection at two-micron-wavelength achieved by a GeSn/Ge multiple-quantum-well (MQW) p-i-n photodiode, exhibiting a 3-dB bandwidth (f3-dB) above 10 GHz for the first time. The epitaxy of device layer stacks was performed on a standard (001)-oriented 300 mm Si substrate by using reduced pressure chemical vapor deposition (RPCVD). The results showed promise for large-scale manufacturing. To our knowledge, this is also the first photodiodes-on-Si with direct radio-frequency (RF) measurement to quantitatively confirm high-speed functionality with tens of GHz f3-dB at 2 µm, which is considered as a promising candidate for the next data communication window. This work illustrates the potential for using GeSn to extend the utility of Si photonics in 2 µm band integrated optical transceivers for communication applications.

Silicon arrayed waveguide gratings at 2.0-μm wavelength characterized with an on-chip resonator

Low-loss arrayed waveguide gratings (AWGs) are demonstrated at a 2.0-μm wavelength. These devices promote rapidly developing photonic applications, supported by the recent development of mid-infrared lasers integrated on silicon (Si). Multi-spectral photonic integrated circuits at 2.0-μm are envisioned since the AWGs are fabricated with the 500-nm-thick Si-on-insulator platform compatible with recently demonstrated lasers and semiconductor optical amplifiers on Si. Characterization with the AWG-ring method improves the on-chip transmission uncertainty to ∼6% compared to the conventional method with an uncertainty of ∼53%. Channel losses of ∼2.4  dB are found, with -31  dB crosstalk per channel. Fully integrated multi-spectral sources at 2.0 μm with pump lasers, low-loss multiplexers, and an output amplifier are now feasible.

III-V-on-Silicon Photonic Integrated Circuits for Spectroscopic Sensing in the 2-4 μm Wavelength Range

The availability of silicon photonic integrated circuits (ICs) in the 2-4 μm wavelength range enables miniature optical sensors for trace gas and bio-molecule detection. In this paper, we review our recent work on III-V-on-silicon waveguide circuits for spectroscopic sensing in this wavelength range. We first present results on the heterogeneous integration of 2.3 μm wavelength III-V laser sources and photodetectors on silicon photonic ICs for fully integrated optical sensors. Then a compact 2 μm wavelength widely tunable external cavity laser using a silicon photonic IC for the wavelength selective feedback is shown. High-performance silicon arrayed waveguide grating spectrometers are also presented. Further we show an on-chip photothermal transducer using a suspended silicon-on-insulator microring resonator used for mid-infrared photothermal spectroscopy.

2.3 µm range InP-based type-II quantum well Fabry-Perot lasers heterogeneously integrated on a silicon photonic integrated circuit

Heterogeneously integrated InP-based type-II quantum well Fabry-Perot lasers on a silicon waveguide circuit emitting in the 2.3 µm wavelength range are demonstrated. The devices consist of a "W"-shaped InGaAs/GaAsSb multi-quantum-well gain section, III-V/silicon spot size converters and two silicon Bragg grating reflectors to form the laser cavity. In continuous-wave (CW) operation, we obtain a threshold current density of 2.7 kA/cm² and output power of 1.3 mW at 5 °C for 2.35 μm lasers. The lasers emit over 3.7 mW of peak power with a threshold current density of 1.6 kA/cm² in pulsed regime at room temperature. This demonstration of heterogeneously integrated lasers indicates that the material system and heterogeneous integration method are promising to realize fully integrated III-V/silicon photonics spectroscopic sensors in the 2 µm wavelength range.