Selecting detection wavelength of resonant cavity-enhanced photodetectors by guided-mode resonance reflectors

Photon-Trapping Microstructure for InGaAs/Si Avalanche Photodiodes Operating at 1.31 μm

With the rapid development of photo-communication technologies, avalanche photodiode (APD) will play an increasingly important role in the future due to its high quantum efficiency, low power consumption, and small size. The monolithic integration of optical components and signal processing electronics on silicon substrate chips is crucial to driving cost reduction and performance improvement; thus, the technical research on InGaAs/Si APD is of great significance. This work is the first to demonstrate the use of a photon-trapping (PT) structure to improve the performance of the InGaAs/Si APD based on an SOI substrate, which exhibits very high absorption efficiency at 1310 nm wavelength while the thickness of the absorption layer is kept at 800 nm. Based on the optical and electrical simulations, an optimized InGaAs/Si PT-APD is proposed, which exhibits a better performance and a higher responsivity compared to the original InGaAs/Si APD.

Metasurface Photodetectors

Photodetectors are the essential building blocks of a wide range of optical systems. Typical photodetectors only convert the intensity of light electrical output signals, leaving other electromagnetic parameters, such as the frequencies, phases, and polarization states unresolved. Metasurfaces are arrays of subwavelength structures that can manipulate the amplitude, phase, frequency, and polarization state of light. When combined with photodetectors, metasurfaces can enhance the light-matter interaction at the pixel level and also enable the detector pixels to resolve more electromagnetic parameters. In this paper, we review recent research efforts in merging metasurfaces with photodetectors towards improved detection performances and advanced detection schemes. The impacts of merging metasurfaces with photodetectors, on the architecture of optical systems, and potential applications are also discussed.

Design of resonant cavity structure for efficient high-temperature operation of single-photon avalanche photodiodes

A novel design of a single-photon avalanche photodiode (SPAD) is proposed based on resonant cavity (RC) structure, and its performance is studied. In the proposed structure, InAlAs/InGaAs distributed Bragg reflectors (DBRs) are employed as top and bottom mirrors and the quantum efficiency (QE) of the absorption region is calculated considering the effect of the RC. Results show that using 12 periods of DBRs as a bottom reflector without incorporation of a top mirror can enhance the QE to about 90% at room temperature. For this RC-enhanced SPAD, a single-photon quantum efficiency (SPQE) is obtained of about 0.35 at T=300  K. For temperatures lower than T=260  K, SPQE is about 1. Results show that although the RC doesn't affect the dark current, for a given SPQE the dark count rate is lower for the RC-SPAD.

Long-wavelength mid-infrared reflectors using guided-mode resonance

We have proposed and fabricated a new mid-infrared reflector using the guided-mode resonance (GMR). The GMR reflector consists of subwavelength Ge grating on GaAs substrate with a low-refractive-index SiOx layer in between. With a total thickness of about 2 μm, a near-100% reflectivity at 8 μm has been obtained both theoretically and experimentally.