Pulsed, injection-seeded optical parametric oscillators, based on quasi-phase-matched media and applied to molecular spectroscopy

Optical parametric oscillator (OPO) devices serve as versatile coherent tunable spectroscopic sources, involving nonlinear-optical conversion of high-power, fixed-frequency laser light to signal and idler output with wavelengths ranging through the infrared, visible and ultraviolet. Injection seeding by a narrowband coherent source, such as a single-mode tunable diode laser (TDL), provides a convenient way to control the optical bandwidth and continuous tunability of a pulsed OPO. This is evident from our earlier work on TDL-seeded pulsed OPOs based on bulk LiNbO/sub 3/ or /spl beta/-barium borate with passive optical cavities that are slightly misaligned to reduce their finesse and thereby support multiple transverse modes for ease of continuous narrowband tuning. We now report the more recent development of tunable TDL-seeded pulsed OPOs that take advantage of quasi-phase-matched (QPM) operation in periodically poled lithium niobate (PPLN). Our modular high-performance spectroscopic system depends on a PPLN OPO with a TDL-seeded ring cavity that is actively controlled by a novel intensity-dip technique.