Design and fabrication of low-loss hydrogenated amorphous silicon overlay DBR for glass waveguide devices

Abstract

We report the use of amorphous silicon (a-Si) and hydrogenated amorphous silicon (a-Si:H) overlays to fabricate low-loss distributed Bragg reflectors (DBRs) for active and passive glass waveguide devices. Overlay material issues, overlay DBR design procedures, and fabrication details are presented. We apply the technology to implement a multiple-wavelength source using an array of overlay DBR waveguide lasers on a single Er/Yb doped, ion exchanged, glass substrate. The lasing wavelengths of the laser array are linearly related to the width of the ion-exchange mask openings. One laser with a 8.5 mm long gain section and a 1.5 mm long overlay DBR had a launched pump power threshold of 29 mW and a 8.5% slope efficiency. We also fabricated a Mach-Zehnder-based, ion exchanged, glass waveguide, optical add-drop multiplexer (OADM) using an a-Si overlay DBR. The 3 cm long OADM exhibited a 24 dB transmission dip with a 3 dB bandwidth of 0.5 nm at the drop wavelength. The throughput loss of the OADM, excluding input and output coupling losses, was approximately 1.9 dB. Theory and measurement results are in good agreement for both the laser array and the OADM.