Transfer-Printing of III - V Photodetector for High-Bandwidth Si -Photonic Integrated Coherent Receiver

Coherent optical communication is being treated as a promising candidate to tackle the increasing demand for faster data rate and band capacity in both data- and telecom domain. With receiving of downstream coherent data in high data rate, novel approaches of high bandwidth coherent receiver design and fabrication will be very necessary. In this work, we demonstrate the integration process of III-V photodetectors on silicon photonic integrated circuits through transfer-printing technique by evanescent coupling, on 8-inch wafer scale. An 8-channel silicon photonic integrated coherent receiver of 42 GHz operation bandwidth for quadrature-phase shift-keying (QPSK) optical communication in C-band application is demonstrated, showing a polarization-independent responsivity of 0.65 -1 A/W with dark current within 90 pA. The integrated photodetectors $(5.3 \mathrm{x}20\mu \mathrm{m}^{2}$ mesa) have a 3 dB bandwidth of 42 GHz at -2 V reverse bias.

I. Introduction

The continuously rapid growth in global data traffic accelerates the immense demand for high speed, low-cost and power efficient data communication technology in data center, long-haul telecom optical networks and mobile wireless cellular base station [1], [2]. The limitations of electrical cable interconnection restrict its capability of handling faster data carriage and increase of link distance [2], [3]. Optical coherent communication technology allows for transmission/reception of optical amplitude, polarization and phase signal in high sensitivity. It provides the great potential on the function of a longer non-relay distance, high band capacity with a good wavelength selectivity, and dispersion compensation [4]. Coherent optical communication systems have been mainly deployed in long-haul telecom backbone networks in the past decade [5]. Nowadays, it further “sink” to the short-reach network which range is less than 80 km, like metro network data center, even local area access network market in near future [6], because of its super large band capacity of a single carrier and high sensitivity. Thereby it can significantly reduce the transmission loss per bit that improving the data transmission efficiency [7]. Thus, the need for lower cost and foot print optical transmitters/receivers with faster data rate are truly urgent. The key to achieve cost and energy efficient systems is to reduce system complexity by the use of high density opto-electrical component integration [1], [8].