Highly Efficient Mid-Infrared Difference Frequency Generation Using a Quasi-Phase Matched Li NbO₃ Ridge Waveguide

Abstract

A laser source in mid-infrared (IR) range is needed for gas sensing because this wavelength range includes a large number of fundamental absorption bands of various atmospheric pollutants. Difference frequency generation (DFG) using quasi-phase matched Li NbO₃ (QPM-LN) waveguides are promising for these laser source.In this review, we describe DFG characteristics of fabricated QPM-LN waveguides using direct-bonding technique.We achieved 40 and 100 %/W conversion efficiency for 3.2 and 2.3μm generation, respectively. Then, we demonstrated CH₄ gas and ¹²CO/¹³CO isotopomer measurement using these waveguides. We also describe wavelength conversion module using V-groove connection technique. Finally, we report compact sub-m W mid-IR laser source, which did not employ a fiber amplifier or a high power solid-state laser.