Field distribution measurements in Q-switched semiconductor lasers

The authors report experimental investigations of the transient behaviour of the fundamental and higher order transverse modes in ultrafast Q-switched lasers. The investigations have shown that the first pulse in a train of pulses emitted from the Q-switched laser always exhibits a TE₀₀ mode distribution, but later pulses display higher order modes. The aim of this work is to control the variation in lateral field pattern to aid future work in modelocking semiconductor lasers. This technique can also be used to screen devices intended for high power operation, which exhibit a TE₀₀ mode at low to medium powers, but at higher power start to exhibit higher mode operation