Over 10 kW peak-power low repetition rate passively mode-locked VECSEL using a saturable Bragg reflector

Reducing the repetition rate is one of the effective ways to increase the peak-power of the mode-locked pulses. However, for a vertical-external-cavity surface-emitting laser (VECSEL), the carrier lifetime in the nanosecond regime limits the further reduction of the pulse repetition rate, or in other words, limits the average output power of the mode-locked laser at low repetition rates, and ultimately restricts the peak-power of the pulses. This work uses a specially designed saturable Bragg reflector to start the mode-locking, and both low repetition rate and high average power are achieved simultaneously in a passively mode-locked VECSEL. When the repetition rate of the pulses is 78 MHz, a peak power of 12.9 kW, twice the reported highest value, is achieved. The pulse repetition rate is further reduced to the lowest value of 67 MHz, and peak-powers of 2.33, 3.00 and 1.23 kW under the fundamental, second-harmonic, and fourth-harmonic mode-locking are demonstrated, respectively. In addition, a theoretical analysis of the influence of the saturation fluence of the saturable absorber on the evolution of the mode-locked pulses is also provided.