Metalens array for InGaAs/InP avalanche photodiodes at optical-communication wavelengths

Abstract

Reducing the dark current of InGaAs/InP avalanche photodiodes (APDs) is an important way to improve the performance of single-photon detection system. Therefore, the active region size of the APD is getting smaller and smaller to reduce the dark current, but that is based on sacrificing the quantum efficiency of the device. In this work, a metalens array is integrated with micro APD array, the metalens structure is proposed to converge light from tens of micrometers to several micrometers and form a focusing effect on the absorber layer to compensate for the loss of absorption efficiency due to the reduction in the size of the APD. The results show that the APD integrated with the metalens array structure behaves enhanced broadband absorption efficiency at optical-communication wavelengths. This design and proposed scheme offer the possibility of reducing the effective size of the APD to 2μm while improving broad-band optical response, owing to its light convergence capability.