An alternative method of changing the pulse duration in a stretcher-compressor pair by changing the gas pressure in the compressor

The relatively narrow bandwidth of neodymium glass requires a much larger stretch ratio of chirped-pulse–amplification (CPA) systems. This factor, together with a large incident angle on the gratings, makes glass CPA systems extremely sensitive to the refractive index of the medium in the stretcher-compressor. High sensitivity of the stretcher-compressor pair for hybrid optical parametric chirped-pulse amplification and an Nd:glass laser to the refractive index was demonstrated in air, vacuum, and carbon dioxide, and a pulse duration close to the transform limit was reached. An alternative way to change the pulse duration was proposed. The pulse duration from the best compression of 500 fs to 30 ps was smoothly varied by changing the air pressure from 10^–6 Torr to 1 atm in the compressor and up to 52 ps in carbon dioxide, while the stretcher and compressor remained untouched. Excellent agreement of the measured pulse duration with theoretical calculations was demonstrated.