• Chinese Optics Letters
  • Vol. 20, Issue 3, 031301 (2022)
Gongqing Li, Xiaofeng Duan*, Weifang Yuan, Yongqing Huang, Kai Liu, and Xiaomin Ren
Author Affiliations
  • State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, Beijing 100876, China
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    We designed a tunable wavelength-selective quasi-resonant cavity enhanced photodetector (QRCE-PD) based on a high-contrast subwavelength grating (SWG). According to simulation results, its peak quantum efficiency is 93.2%, the 3 dB bandwidth is 33.5 GHz, the spectral linewidth is 0.12 nm, and the wavelength-tuning range is 28 nm (1536–1564 nm). The QRCE-PD contains a tunable Fabry–Perot (F-P) filtering cavity (FPC), a symmetrical SWG deflection reflector (SSWG-DR), and a built-in p-i-n photodiode. The FPC and the SSWG-DR form an equivalent multi-region F-P cavity together by multiple mutual mirroring, which makes the QRCE-PD a multi-region resonant cavity enhanced photodetector. But, QRCE-PD relies on the multiple-pass absorption enhanced effect to achieve high quantum efficiency, rather than the resonant cavity enhanced effect. This new photodetector structure is significant for the application in the dense wavelength division multiplexing systems.

    1. Introduction

    High speed[1], high quantum efficiency, narrow spectral linewidth[26], and broad wavelength-tuning range[47] are the critical performances for a photodetector applied in dense wavelength division multiplexing (DWDM) systems[8]. Due to the limitation of inherent efficiency bandwidth product, traditional normal-incidence photodetectors cannot achieve high speed and high quantum efficiency simultaneously. The resonant cavity enhanced photodetector (RCE-PD) can break this restriction by inserting the absorption region into the Fabry–Perot (F-P) resonant cavity[911]. However, the absorption effect will reduce the quality factor of the resonator, so that the spectral linewidth of the RCE-PD will be broadened. For a conventional RCE-PD, the spectral linewidth is commonly wider than 20 nm, which is inapplicable for DWDM systems.