Frequency-agile kilohertz repetition-rate optical parametric oscillator based on periodically poled lithium niobate

We report kilohertz repetition-rate pulse-to-pulse wavelength tuning from 3.22 to $3.7 \mu \mathrm{m}$ in a periodically poled lithium niobate (PPLN) optical parametric oscillator (OPO). Rapid tuning over $400 {\text{cm}}^{-1}$ with random wavelength accessibility is achieved by rotation of the pump beam angle by no more than 24 mrad in the PPLN crystal by use of an acousto-optic beam deflector. Over the entire tuning range, a near-transform-limited OPO bandwidth can be obtained by means of injection seeding with a single-frequency $1.5‐\mu \mathrm{m}$ laser diode. The frequency agility, high repetition rate, and narrow bandwidth of this mid-IR PPLN OPO make it well suited as a lidar transmitter source.