Broadly tunable laser-diode-based mid-infrared source with up to 31 microW of power at 4.3-microm wavelength

High-power single-spatial-mode near-IR laser diodes are mixed in periodically poled LiNbO(3) (PPLN) to generate broadly tunable mid IR-radiation. Conversion efficiencies to the mid IR up to 0.017%/W are demonstrated, and up to 31 microW of power is generated at the spectroscopically important 4.3-microm wavelength. We achieved broadband mid-IR tunability by mixing a wavelength-tunable laser-diode pump source with a fixed-wavelength master oscillator power amplifier laser-diode signal source in a PPLN sample that has a poling period that varies from 21.0 to 22.6 microm in the direction transverse to the beam propagation. We generated mid-IR radiation from 4.1 to 4.3 microm with these laser sources, using a fixed 22.0-microm period region of the sample.