Method for operating q-switched lasers with intracavity frequency conversion

Abstract

An intracavity frequency converted, Q-switched laser and method for operating such laser to obtain high output power in secondary pulses at a converted frequency. The secondary pulses are generated by a intracavity frequency conversion element from primary pulses at the fundamental wavelength. In accordance with the invention, after the primary and secondary pulses are generated the Q-switch is turned back on before the gain is fully depleted in the generation of the primary pulse. In particular, the Q-switch is turned back on such that a certain amount of energy of the primary pulse is retained in the laser, but late enough so that a majority of the secondary pulse is out-coupled from the laser. The Q-switched laser is well-suited for use at pulse repetition rates larger than 1/&tgr;, where &tgr; is an upper state lifetime (fluorescence lifetime) of the laser. Specifically, the laser can be operated at repetition rates of 10 kHz and higher, e.g., 30 kHz and higher to obtain significant increases in output power of the secondary pulses. Furthermore, the method and laser of the invention are compatible with various types of frequency conversion elements and processes including second harmonic generation, third harmonic generation, fourth harmonic generation, difference frequency generation, sum frequency generation, parametric amplification and parametric generation.