Compact and widely tuneable coherent mid-infrared sources give access to manifold applications across the molecular fingerprint spectral region; for instance, making use of techniques like dual-comb and Fourier Transform spectroscopy. A significant challenge to access the mid-infrared region is the availability of high-quality nonlinear media. Quasi-phase-matching (QPM) in orientation-patterned gallium phosphide (OP-GaP) is an attractive approach since it permits realizing highly efficient and compact sources of tunable radiation in the mid-infrared fingerprint regime. Still, to date the applications using OP-GaP have been limited by the quality and availability of GaP substrates.

The present Optical Materials Express publication proposes and demonstrates the use of GaAs as the growth substrate. The OP-GaP on GaAs QPM crystals were grown over just 9 hours, including a fan out grating structure that permits wavelength tuning spanning from 3.9 μm to 12.0 μm. Significant output powers, up to 150 mW at 5.6 μm, were demonstrated, comparable to other similar systems.

The new OP-GaP growth process outlined by Schunemann et al. shows how to scale the performance of the OPOs and to boost the output powers for realistic applications in the fingerprint regime.

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