Time-resolved M(2) of nanosecond pulses from a Q-switched variable-reflectivity-mirror Nd:YAG laser

Time-resolved M(2) numerical computation and experimental measurements of nanosecond pulses from a Q-switched variable-reflectivity-mirror Nd:YAG laser are presented for the first time to our knowledge. The beam quality parameter is seen to vary approximately from 1 at the beginning to 2 at the end of a high-energy pulse, with a value of 1.35 at the peak of the pulse, which also corresponds to the M(2) obtained from the time-averaged detection of the pulse profile.