Hybrid pulse compressor for 1.5 mJ, sub-23 fs CPA system

Chirped-pulse amplification (CPA) has become a common technique for damage-free amplification of the light pulses to TW-level or even higher. The standard CPA systems often use diffraction grating based stretchercompressor systems or bulk material as the stretcher and pairing double-prism as pulse compressors. Prism compressors are preferred over grating based systems, if the required stretching factor is small, because of their high throughput and smaller amount of higher-order dispersion. In case of a prism compressor, the amplified pulses enter positively chirped. The prism compressor introduces sufficient negative group-delay dispersion (GDD) due to the geometrical path, so that the pulses are slightly overcompressed (negatively chirped) before entering the last prism. The pulses then are finally compressed by the positive GDD of the bulk material while propagating through the last prism. Since the final compression takes place in bulk material, self-phase modulation (SPM) can occur even at modest pulse energies which in turn causes spectral narrowing in the compressed pulses (Fig. 1a) owing to the negative chirp of the pulses. Hybrid pulse compression (HPC) [1] was proposed to overcome this SPM in the prism material. Here, the pulses after the amplifier are overcompressed by increasing the prism separation. The pulses still maintain their negative chirp after the last prism and are finally compressed by the positive-dispersive mirrors (PDM). For high energy (and hence intensity) pulses, ever more negative chirp is required to avoid SPM. Therefore the required prism separation quickly becomes inconvenient and may even lead to spectral clipping in the second pair of prisms. Moreover, the increased prism separation also results in a change in the higher-order dispersion components, which in turn requires additional dispersion management.