Programmable phase compensation in a multipass Ti:sapphire CPA system

The programmable control over the phase of sub-30-fs pulses in a 10-pass chirped-pulse amplifier using a pulsed stretcher incorporating a programmable liquid crystal spatial light modulator (SLM) is demonstrated. The distinct advantage of this method is that almost arbitrary spectral phase profile can be programmed into the SLM. The amplifier is seeded by 15-fs 2-nJ pulses produced by a Ti:sapphire laser. Pulses are fed into a pulse stretcher with a 128 element liquid crystal SLM in this symmetry plane. The wavelength dependence of the grating diffraction efficiency over the effective bandwidth of the pulse leads to substantial reduction in spectrum width limiting the output pulse duration to 20 fs.