I really do not know much about laser. But I need a pulsed laser with duration about 100ns or less. The repetition rate should not exceed 2 kHz (slow rate with more concentrated energy in each pulse is best). I have seen many laser modules with TTL modulation mode. Are these pulsed lasers? If it is, what is the typical duration of each pulse? And how to implement TTL modulation? Can I use a function generator to generate square waves as the input?