Laser strobe for Point Grey camera
Laser diodes themselves can pulse as fast as you like - down to nanosecs - actual speed depends on the driver.
It is not generally practical to increase power at lower duty cycles as the limiting factor tends to be optical damage rather then purely thermal. 
Bear in mind that unless you need the coherence or tight beam of a laser, normal power LEDs will typically give you more output power then lasers, and are more amenable to increasing power for short durations.