Intensive picosecond range pulses obtained by spectral selection from Q-switched GaAlAs/GaAs SH lasers

摘要

A significant wavelength separation was found between the shot-pulsed mode and stationary lasing in the emission band of a Q-switched SH laser. This feature allowed Q-switching mode selection by means of a band-pass optical filter. Anexperimentally observed isolated 35 Ps pulse with a power of 60 W is a very attractive feature for optical radars and other applications. After spectral filtering, no light emission with an intensity higher than 0.3 W, except the short intensiveQ-switching pulse was observed.The physical nature of the emission band separation for various modes is considered. The Q-switching lasing mode is attributed to the optical transitions between free-carrier states, being caused by the energy relaxation of the carriers when the pumpingcurrent pulse is abrupt. During the current pulse the carriers were heated by a powerful electric field across the active region of the diode.The Q-switched pulse spectrum also contains other modes corresponding to transitions with band-tail states involved, which produce a long, low-intensity tail after the short intensive pulse. We suppressed this tail spectrally using significant energyseparation between the band and tail states in strongly compensated semiconductor material.