Abstract: Improved mode-locked optical parametric oscillator apparatus comprises a mode-locked pump laser having a cavity with a predetermined effective length l.sub.p and a parametric oscillator having a nonlinear crystal, such as lithium niobate (LiNbO.sub.3), and singly resonant mirrors spaced apart by an effective distance l.sub.o which is substantially less than l.sub.p, i.e., l.sub.p .apprxeq.nl.sub.o where n.apprxeq.5-50. The interaction of the mode-locked pump output with the nonlinear crystal produces parametric outputs at signal (f.sub.s) and idler (f.sub.i) frequencies, the parametric oscillator mirrors being singly resonant at one of those two frequencies. The parametric oscillator may be disposed either externally of or within the pump cavity and the pump laser optionally may be Q-switched.

Abstract: A pulsed solid state tunable laser comprises a Q-switched pump laser at kilohertz (kHz) pulse repetition frequencies and a non-centrosymmetric Raman crystal, such as lithium iodate (LiIO.sub.3), through which the pump beam is directed at an angle .theta. to the crystal optical axis. Stimulated Raman scattering (SRS) occurs in the crystal to produce Stokes lines at substantial average output powers, which lines react with the pump signal in the nonlinear crystal at predetermined values of .theta. to generate second harmonics (SHG) and sum frequencies (SFG) of the pump and Stokes lines which constitute visible light outputs. Changing the value of .theta. by rotating the crystal, for example, permits the apparatus to be step-tuned to phasematch the signals and produce visible light outputs at a plurality of wavelengths.

Abstract: Stimulated Raman scattering (SRS) at kHz pulse repetition rates is substantially improved with a laser configuration in which the Raman oscillator mirrors within the laser resonator are removed and the laser mirrors are used for both the laser and the Raman (Stokes) resonators. This sharing of the laser resonator by the Raman oscillator has increased the average power and stability of the first and second Stokes wavelengths, has reduced optical wear on the mirrors, and has resulted in a substantially simplified resonator design.