Spectral broadening and phase shaping of mid-IR pulses

Efficient spectral broadening of mid-IR short pulses was achieved by use of self-phase modulation in a GaAs single crystal. The spectral bandwidth of the pulse at the center wavelength of 5 micron increased from 540 nm to 2060 nm. Subsequent dispersive propagation compressed the temporal duration down to three optical cycles. The precise shaping of mid-IR pulses was achieved by use of a semiconductor acousto-optic modulator. The spectral interferometry cross-correlation measurements evaluated the shaped phase with good reproducibility.