Improved multi-layer glass-bonded QPM GaAs crystals for non-linear wavelength conversion into the mid-infrared

Abstract

Optical parametric oscillators (OPOs) offer a route to powerful tunable output in the mid-infrared (mid-IR). Mid-IR OPOs exploit wavelength conversion of near-infrared lasers within non-linear optical materials. A new approach to engineering suitable non-linear OPO materials is being developed as an alternative to conventional chalcopyrite crystals such as ZnGeP₂. These new materials use commercially available, high-optical quality gallium arsenide (GaAs) wafers and a novel glass-bonding (GB) process to assemble quasi-phase matched (QPM) multilayer structures. The assembled QPM GaAs stack must have low optical loss and a large useable aperture and needs to be produced reliably with a minimum of 50 layers. Results from a recent sequence of 50-layer GBGaAs stack fabrication will be presented. Of the six stacks successfully bonded two had a useable aperture of approximately 20 mm² (40% of the maximum available). Of these, one has the lowest absorption and transmission loss per layer (0.07% measured at 2 μm) of any multi-layer glass-bonded QPM GaAs stack produced to date. By adjusting the load distribution at the edges of the stack during bonding the useable optical aperture was increased to nearly 90%. Results from non-linear wavelength conversion experiments into the mid-infrared using multi-layer GBGaAs crystals will be presented.