A novel Q-switch device enables significant quality and value improvement for a Q-switched
laser system by achieving a significant reduction of mode-beating
noise during the pulsed output. The origin of mode-beating
noise in a Q-switched
laser is a result of high
gain availability and amplification of competing standing-
waves in formation, whose optical frequency is a product of
natural selection via spatial hole burning in the
gain medium. The novel Q-switch device employs an active, electro-
optics or acousto-
optics, Q-switch in combination with a saturable absorber device, to provide an optimized soft opening of the
optical path and a controlled timing of a Q-switched
laser. This novel combination offers larger modulation loss than otherwise possible with the active modulator alone, and it allows for higher
gain build-up and energy extraction efficiency. Specifically, it will enable a low-
voltage modulator (<100 V) for high gain (small-
signal gain >10) and Q-switched operation at high repetition rate (>10 kHz). The combination is devised to slow down the
signal build-up and to sweep the fundamental
longitudinal mode frequency at least within the
free spectral range of the
resonator, such that it varies adiabatically during the Q-switched pulse formation. A laser geometry amenable to high gain and high power is proposed for use in conjunction with the proposed novel Q-switch device. The invention will enable the deployment of cost-effective Q-switched lasers operating in both single-longitudinal and single-transverse (TEM00) mode.