Efficient light coupling into in-plane semiconductor nanomembrane photonic devices utilizing a sub-wavelength grating coupler

Harish Subbaraman,Ray T Chen,John Covey,Xiaochuan Xu

doi:10.1364/oe.20.020659

Abstract

We report a subwavelength grating (SWG) coupler for coupling light efficiently into in-plane semiconductor nanomembrane photonic devices for the first time. The SWG coupler consists of a periodic array of rectangular trenches fabricated on a silicon nanomembrane (SiNM) transferred onto a glass substrate. At a wavelength of 1555.56 nm, the coupling efficiency of the fabricated 10 µm wide, 17.1 µm long SWG is 39.17% (-4.07 dB), with 1 dB and 3 dB bandwidths of 29 nm and 57 nm, respectively. Peak efficiency varies by 0.26 dB when measuring 5 fabricated grating pairs. Coupling efficiency can further be improved with an improved SiNM transfer process. Such high efficiency couplers allow for the successful realization of a plethora of hybrid photonic devices utilizing nanomembrane technology.

Highlights

Progress in silicon photonics over the last 15 years, utilizing silicon-on-insulator (SOI) technology, has significantly moved conventional silicon VLSI to high speed, high bandwidth photonics with lower power consumption
Of the various semiconductor nanomembranes (SiNM) studied, silicon nanomembranes are a natural choice for the development of high performance circuits and devices owing to a strong history of silicon photonics and microelectronics development
We report the first subwavelength grating coupler (SWG) to achieve low-loss coupling into in-plane SiNM-based photonic devices

Summary

Introduction

Progress in silicon photonics over the last 15 years, utilizing silicon-on-insulator (SOI) technology, has significantly moved conventional silicon VLSI to high speed, high bandwidth photonics with lower power consumption. Silicon nanomembranes are comprised of a very thin sheet of crystalline silicon that can be released from a silicon-on-insulator wafer [1] Such membranes can be transferred and redeposited on other rigid or flexible hosts such as glass, polyethylene teraphthalate (PET), Kapton, etc using low temperature processes, providing hybrid integration and high performance devices. Similar to their SOI counterpart, silicon nanomembranes on other substrates are expected to exploit the same CMOS processing technologies that have resulted in widespread success of silicon photonics. For successful in-plane SiNM photonic devices, one needs to overcome the challenges of intricate device development and light coupling on foreign substrates. Utilization of such a coupler can rapidly push flexible photonics technology forward, opening avenues for a wide range of useful devices

Design and Fabrication

Device characterization

Conclusion