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 (TEM.sub.00) mode.