Low loss orientation-patterned gallium arsenide (OPGaAs) waveguides for nonlinear infrared frequency conversion

Date of Award

2012

Degree Name

Ph.D. in Electrical Engineering

Department

Department of Electrical and Computer Engineering

Advisor/Chair

Advisor: Andrew Sarangan

Abstract

The mid-IR frequency band (λ = 2-5 æm) contains several atmospheric transmission windows making it a region of interest for a variety of medical, scientific, commercial, and military applications. Recently there has been a growing interest in using orientation-patterned semiconductors such as orientation-patterned gallium arsenide (OPGaAs) to achieve frequency conversion in this region. GaAs has a large nonlinear coefficient, broad transparency range, and a well-developed fabrication technology allowing for the manufacture of nonlinear integrated optical devices such as waveguides. By confining the nonlinear pump beam throughout the length of a waveguide one can achieve very high field intensities while at the same time overcoming the diffraction normally associated with tight focusing of Gaussian beams. However, device performance in OPGaAs waveguides has been limited by large propagation losses resulting from the unique nature of the material. In this dissertation I report an OPGaAs/OPAlxGa1-xAs embedded ridge waveguide design which, combined with a new growth process using alternating MOCVD growth and chemical mechanical polishing (CMP), is capable of achieving the low losses necessary to function effectively as a nonlinear gain material. Our waveguide was designed to be single mode from 2-10 æm, based upon a series of numerical simulations to determine the effective indices of the waveguide across the mid-IR band, which was crucial for accurate calculation of the grating period Λ needed for quasi-phasematching. Record low RMS surface roughness values of 5 nm were obtained using this new growth process. In addition, record low waveguide losses of 1.0 dB/cm were measured, validating our theoretical predictions, and nonlinear gain was investigated in an optical parametric amplifier (OPA) experiment.

Keywords

Infrared image converters, Wave guides Design and construction, Gallium arsenide semiconductors, Electrical engineering; waveguides; nonlinear optics; lasers; infrared

Rights Statement

Copyright © 2012, author

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