Abstract

Quasi-phase-matched wavelength conversion in orientation patterned GaAs (OP-GaAs) is a useful method to create coherent long-wave IR radiation. GaAs offers wide transparency range between 0.9 and 17 μm, low absorption, high thermal conductivity and large nonlinear susceptibility (d₁₄ ≥ 90 pm/V for GaAs). Recently, an all-epitaxial method for fabrication of orientation-patterned structures in GaAs has been developed.¹ Difference frequency generation (DFG) of the idler wavelength around 8 μm was demonstrated recently in thick (0.5 mm) OP-GaAs device showing excellent material properties, near theoretical wavelength tuning curve and efficiency.² A light source for high sensitivity long-wave IR spectroscopy should demonstrate narrow linewidth, wide continuous scanning capability and power levels above 1 μW. Typical vibration modes of organic molecules can be found at wavelengths around 3 μm where other light sources are available.³ However, species can be more easily identified using 7-10 μm spectroscopy due to higher intensity, more specific vibrational modes that absorb there. In this presentation we demonstrate continuous tuning of a potential spectroscopic light source between 7.95 and 8.6 μm using both wavelength tuning of the pump and signal sources, and device temperature tuning.

© 2002 Optical Society of America