Amorphous silicon waveguide components for monolithic integration with InGaAsP gain sections

Abstract

ABSTRACT Low loss, single mode rib waveguides, based on PECVD deposited multi-layer amorphous silicon are fabricated. These waveguide are refractive index and mode-matched to III/V laser waveguides. Methods for monolithic integration of these passive amorphous silicon waveguides with InGaAsP/InP gain sections are demonstrated. Results of a multi-wavelength laser based on an amorphous silicon arrayed wavegu ide grating integrated on a single chip with InGaAsP gain sections are presented. Keywords: Photonic integrated circuits, amorphous silicon, waveguides 1. INTRODUCTION Amorphous silicon is a material that is widely used for solar cells and for thin film transistors in display applications. Amorphous silicon and amorphous silicon alloys such as am orphous silicon nitride or amorphous silicon carbide have received little attention for us e as optical waveguides 1,2 or for application in integrated optics 3 . Hydrogenation of amorphous silicon for termination of dangling bonds results in excellent loss properties in the telecommunication windows (1300nm, 1550nm). This makes this material suitable for high quality passive circuits. Incorporation of nitrogen allows adjustments of the refractive index of these materials covering a broad range of 2-3.5. Optical waveguides can be formed with layers of different refractive indices. And most notably it is possible to match the refractive index of amorphous silicon to the values of InP and its alloys (InGaAsP, GaInAlAs) used in active photonic components. Hydrogenated amorphous silicon alloys can be deposited with plasma enhanced chemical vapor deposition (PECVD) processes at temperatures around 200 – 250 °C making them compatible with III/V materials. This simple and high yield process allows for easy and reproducible de position on flat or structured surfaces. Monolithic integration of passive waveguide based devices with active elements such as gain sections has been demonstrated using various techniques using InP / InGaAsP based structures for both active and passive parts