The design and performance of a third-generation megahertz-rate pulse burst laser system is described. The third-generation system incorporates two distinct design changes that distinguish it from earlier-generation systems. The first is that pulse slicing is now achieved by using an economical acousto-optic modulator (AOM), and the second is the use of a variable pulse duration flashlamp driver that provides relatively uniform gain over a ~700 mus window. The use of an AOM for pulse slicing permits flexible operation such as pulse-on-demand operation with variable pulse durations ranging from 10 ns to DC. The laser described here is capable of producing a burst of laser pulses at repetition rates as high as 50 MHz and peak powers of 10 kW. Second-harmonic conversion efficiency using a type II KTP crystal is also demonstrated.