The conversion efficiency in second-harmonic generation of an amplified beam in a master-oscillator power amplifier copper-vapor laser (CVL) is lower than that of the oscillator beam alone. This lower efficiency is often vaguely attributed to wave-front degradation in the amplifier. We investigate the role of wave-front degradation and thermal dephasing in the second-harmonic generation of a CVL from a beta-barium borate crystal. Choosing two beams with constant intrapulse divergence, one from a generalized diffraction filtered resonator master oscillator alone and other obtained by amplifying oscillator by use of a power amplifier, we show that at low flux levels the decrease in efficiency is due to wave-front degradation. At a fundamental power above the critical power for thermal dephasing, the decrease is due to increased UV absorption and consequent thermal dephasing. Thermal dephasing is higher for the beam with the lower coherence width.
© 2005 Optical Society of America
(040.1490) Detectors : Cameras
(140.1340) Lasers and laser optics : Atomic gas lasers
(140.4780) Lasers and laser optics : Optical resonators
(190.2620) Nonlinear optics : Harmonic generation and mixing
Om Prakash, Sudhir Kumar Dixit, and Rajiva Bhatnagar, "Thermal dephasing in second-harmonic generation of an amplified copper-vapor laser beam in beta barium borate," Appl. Opt. 44, 1719-1725 (2005)