Megahertz-repetition-rate Nd:glass fiber laser

Stable trains of 100-200-ns-long pulses are obtained at 0.46-1.06-MHz repetition rates in a Nd:glass fiber laser by driving large-amplitude relaxation oscillations at or below their resonance. Numerical simulations agree qualitatively with temporal profiles of the output power. We show that the maximum pulse-repetition rate of a relaxation-oscillation laser increases as the square root of pump power at low P and that its theoretical upper limit is close to the pulse rate of a mode-locked laser.