Diode-pumped, cryogenically cooled, femtosecond burst mode laser

We present a novel approach for the construction of a high energy, high power burst mode laser system, based on diode pumped cryogenically cooled Yb:CaF₂. The system consists of a frontend producing pulses of 300 fs duration with 1 MHz. Bursts of 1000 subsequent pulses are cut from the continuous train by an electro optical modulator. Afterwards the duration of the individual pulses is stretched to 50 ps. The amplifier system consists of two amplifiers. Both amplifiers utilize mirror based relay imaging schemes to allow for a sufficient number of extraction passes for achieving efficient energy extraction. The goal parameters of the system are to achieve a total energy of 5J per burst with a repetition rate of 10Hz. Amplification results for the first of two amplifiers are demonstrated. A total output energy of 480 mJ was achieved corresponding to an optical to optical efficiency from absorbed pump energy to extracted energy of more than 17%. Single pulse energies of up to 7.5mJ are generated when changing to less pulses per burst. To achieve a constant energy from pulse to pulse during the burst we present a technique based on the modulation of the laser diode current during one pulse. With this technique the gain variation during the burst was than 5% peak to peak.