Controlling frequency chirp in a ns-pulsed, single-longitudinal-mode, injection-seeded PPKTP optical parametric oscillator

Measurements of frequency chirp in a ns-pulsed, single-longitudinal-mode, injectionseeded optical parametric oscillator identify factors influencing the magnitude and pulse-to-pulse stability of this chirp. Methods to minimize chirp are identified. 02003 Optical Society of America OCIS codes: (190.4360) Nonlinear optics, devices; (190.4970) Parametric oscillators and amplifiers Narrowband, nanosecond-pulsed tunable coherent radiation for hgh-resolution spectroscopy can be generated by injection seeding an optical parametric oscillator (OPO) [ 11. A coherent light source with well-characterized optical phase and good pulse-to-pulse stability facilitates such applications [2,3]. We use a heterodyne technique to measure the optical phase characteristics of a ns-pulsed periodically poled KTiOP04 (PPKTP) OPO that is injectionseeded by a cw tunable diode laser (TDL), emulating previous work on pulse-amplified, single-mode cw lasers [2.3]. We investigate how frequency clllrp in a TDL-seeded PPKTP OPO is affected by varying the experimental con&tions. Figure 1 shows our intensity-dip control design [4,5] that allows continuously tunable single-longitudinal-mode (SLM) operation of the TDL-seeded pulsed PPKTP OPO with a signal tuning m g e of 834 85 1 nm. The PPKTP ring-cavity OPO is pumped by either of two frequency-doubled SLM Nd:YAG lases with differing FWHM pulse durations, -8 11s and -30 ns. A portion of the seed beam is split off before the OPO and frequency-shifted by -730MHz via an acousto-optic modulator (AOM). This frequency-shfted cw light is combined with pulsed OPO signal radiation to produce a beat signal on a 1-GHz photodiode. Photodetector + BeatSignal Electronics 1 I I 1 I I I I I 1 Chopper BS3n .