Generation of 0.5 mJ, few-cycle laser pulses by an adaptive phase modulator.

Previously, pulses shorter than 4 fs were generated by compressing white light from gas-filled hollow-core fibers with adaptive phase modulators; however, the energy of the few-cycle pulses was limited to 15 microJ. Here, we report the generation of 550 microJ, 5 fs pulses by using a liquid crystal spatial light modulator in a grating-based 4f system. The high pulse energy was obtained by improving the throughput of the phase modulator and by increasing the input laser energy. When the pulses were used in high harmonic generation, it was found that the harmonic spectra depend strongly on the high order spectral phases of the driving laser fields.