Intracavity parametric generation of nanosecond terahertz radiation using quasi-phase-matching

We report the use of quasi-phase-matching techniques based on periodically-poled MgO:LiNbO3 for the generation of nanosecond duration pulses of terahertz radiation in intracavity optical parametric oscillators. Multiple idler-waves are generated with temporal studies indicating that the initiating process is the expected parametric down-conversion, but followed by cascaded difference frequency generation. A number of grating geometries have been explored, revealing the presence of dual solutions for the quasi-phase-matching process in the general case. Choice of grating parameters so as to minimize oscillation threshold while simultaneously ensuring effective extraction of the THz radiation is considered. (C) 2010 Optical Society of America