Multigrating quasi-phase-matched optical parametric oscillator in periodically poled LiNbO3

We report a widely tunable quasi-phase-matched optical parametric oscillator that uses periodically poled LiNbO3 with a multigrating structure. The device is tuned by translation of the crystal through the resonator and pump beam, with no realignment needed. With a 1.064-mu m acousto-optically Q-switched Nd:YAG pump laser, we produced noncritically phase-matched tunable IR output from 1.36 to 4.83 mu m. The threshold was 6 mu J for a 26-mm interaction length. The extraordinary polarization of LiNbO3 has better IR transmission than does the ordinary polarization, permitting operation at longer wavelengths with d(33) quasi-phase matching than with conventional Type I birefringent phase matching. (C) 1996 Optical Society of America.