Monolithic Integrated Optical Receiver With a Metal Reflector-Assisted Surface Grating Coupler

High-speed optical receivers with high-efficiency power collection capability are highly demanded in an optical wireless communication system to achieve high sensitivity due to the power-limited eye safety regulation. A cascaded aperture optical receiver enabled by a waveguide photodetector and a grating coupler is a promising candidate because of its advantage of optimizing the electrical performance and the light collection independently. Here, we propose using a metal reflector (MR)-assisted grating coupler to increase the coupling efficiency further. A sensitivity-enhanced monolithic integrated optical receiver with an MR-assisted grating coupler is realized for the first time, which is demonstrated on the Indium Phosphide membrane on Silicon platform. The maximum −3 dB bandwidth and the external responsivity of the waveguide photodetector inside the proposed optical receiver are 52.2 GHz and 0.31 A/W, respectively. A back-to-back receiver sensitivity of −4.75 dBm for a 10 Gb/s OOK signal at the 7% FEC limit is achieved. With the enhancement of an MR, the achieved sensitivity is calculated to be 1.5 dB higher based on the measured results compared with the cascaded aperture optical receiver without an MR on the same platform.

I. Introduction

Optical wireless communication (OWC) is attractive as a promising technique to provide a large bandwidth to serve the exponential growth of data traffic caused by large-scale wireless connectivity in indoor networks [1]. An optical receiver, a key component for an OWC system, is used to collect and convert the optical signal into electrical signal. Due to the eye safety regulation, the maximum transmitted power of the infrared laser beam in an OWC link should be below 10 dBm for [2]. A receiver with a large aperture can efficiently collect enough optical power to allow a sufficient power budget for high-speed optical wireless transmission [3].