Generation of laser pulses by Q-switching and cavity dumping and their amplification by a microwave excited laser

Abstract

Q-switched low-pressure lasers allow both the production of maximum laser pulse power and high average laser power at high pulse repetition rates. A Q-switched laser oscillator amplifier system consisting of a DC discharged, wavelength tunable and diffusion cooled oscillator and a microwave excited amplifier is described. By mechanical Q-switching of the oscillator laser pulses with a pulse repetition rate of 4 - 200 kHz and beam quality can be produced. After the amplification the peak power reaches 0.9 MW at a pulse repetition rate of 10 kHz and 0.2 MW at a 100 kHz repetition rate. The pulse duration (FWHM) is about 0.2 s. The maximum average power of 7 kW in the Q-switched mode reaches nearly the maximum cw laser power of 10 kW (with beam quality). The laser pulse duration can be shortened by the combination of cavity dumping and electro-optical Q-switching. This pulsed operation leads to laser pulses with 35 ns pulse duration and 1.9 MW maximum power at a pulse repetition rate of 10 kHz and an average laser power of 0.8 kW. The self-oscillation of the oscillator amplifier system can be suppressed by an optical shutter between oscillator and amplifier. The laser beam power can be calculated by a six-temperature model including rotational relaxation, intramode and intermode vibrational energy exchange.