Longwave-infrared optical parametric oscillator in orientation-patterned gallium arsenide

Date of Award

2011

Degree Name

M.S. in Electro-Optics

Department

Department of Electro-Optics and Photonics

Advisor/Chair

Advisor: Peter E. Powers

Abstract

Coherent tunable laser sources in the longwave infrared (LWIR) spectral region are in high demand for military applications. Most lasers cannot produce outputs far into the infrared region, and therefore a conversion process is needed to achieve desired wavelengths. Quasi-phase matching is a technique that spatially modulates the nonlinear properties of a given material, periodically reversing the induced nonlinear polarization to ensure positive energy flow from the pump source to the converted fields, subject to conservation of energy and momentum. Through the use of optical parametric oscillation (OPO), and nonlinear quasi-phase matched orientation-patterned gallium arsenide (OPGaAs), producing LWIR wavelengths is possible. The OPGaAs OPO was pumped with a Q-switched 2.054μm Tm,Ho:YLF laser. As a precursor to the LWIR OPGaAs OPO, different resonator geometries were explored with a midwave (MWIR) OPGaAs OPO utilizing both SRO and DRO mirror sets. While thresholds increased with cavity length, the slope efficiencies remained relatively similar with the respective mirror set. The LWIR OPGaAs OPO explored the performance using two separate cavity configurations, an SRO and an asymmetric cavity; and five different OPGaAs samples representing three different grating periods. The highest slope efficiency in the SRO LWIR cavity was found to be ̃29%, with threshold values of ranging from ̃45-90μJ. The slope efficiencies for the asymmetric cavity range from ̃4-16% while experiencing higher thresholds of ̃150-220μJ, lower overall output power, and increased cavity instability. At higher pump energies, rollover was observed in both cavity configurations. SNLO was used to model the OPO output in the hopes that it might provide some insight into this behavior. The theoretical performance plot fit the acquired data decently but failed to predict the behavior at the higher energies. Spectroscopic data were collected for both OPO signal and idler output, presenting good agreement with theoretical tuning curves.

Keywords

Optical parametric oscillators, Gallium arsenide semiconductors, Tunable lasers, Nonlinear optics Materials

Rights Statement

Copyright © 2011, author

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