Low dark current and high bandwidth evanescent wave coupled PIN photodetector array for 400 Gbit/s receiving system

Abstract

Compared with surface and edge incident photodetectors, evanescent coupling photodetector (ECPD) has high bandwidth and high quantum efficiency, so it has a broad application prospect in the field of high-speed optical communication. The evanescent wave coupled photodetector is composed of a diluted waveguide, a single-mode ridge waveguide and a PIN photodiode. By directional evanescent wave coupling, the coupling efficiency of the incident light from the fiber to the absorption core of the photodetector is improved. In this paper, the structure design, experimental preparation and test results of an indium phosphorus based evanescent wave coupled photodetector array are introduced in detail. The test results show that the dark current of the evanescent wave coupled photodetector array is as low as 215 pA and 1.23 pA under –3 and 0 V bias, respectively. When the active area is 5 μm × 20 μm, the device still has a high responsivity of 0.5 A/W (without antireflection film). The high frequency performance of the detector is tested. The bandwidth of each detector is more than 25 GHz, and the total bandwidth is more than 400 GHz. Any optical device can be integrated. The detector array can be applied to the WDM receiving system of 400 Gbit/s and coherent receiving system of 200 Gbit/s.