Adaptive Shaping of High-Power Broadband Femtosecond Laser Pulses
We demonstrate the implementation of a feedback controlled pulse shaping device in a femtosecond high-power Ti:sapphire laser system. The laser system consists of a mirror dispersion controlled oscillator and a multipass amplifier with a pairing double prism compressor. The system provides pulses with a duration of 30 fs and an energy of up to 1.2 mJ per pulse at 1 kHz repetition rate. The phase distorted output pulses are phase modulated with a high resolution spatial light modulator (SLM). The pulse shaper consists of an all-reflective zero-dispersion compressor equipped with a liquid crystal array. For adaptive compression of the amplified pulses a feedback loop is implemented. A two-photon process is used to monitor the temporal pulse characteristics. To achieve the shortest possible pulse an evolutionary algorithm controls the pulse shaper utilizing the two-photon signal as feedback. With this set-up transform limited pulses are achieved. Detailed investigations of algorithm parameters and their effect on convergence behaviour have been performed and are compared with the experimental findings.
KeywordsFemtosecond Laser Pulse Spatial Light Modulator Spectral Phase Acousto Optic Modulator Reproduction Probability
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