Broadening, nonlinear filtering, and compression of microjoule energy laser pulses at 1 µm wavelength

Abstract

In this work, we experimentally demonstrate the generation of 30 nm of spectral broadening in a bulk cadmium sulfide (CdS) semiconductor generated by a 280 fs long pulse at 1.024 µm wavelength and with a microjoule energy level. Using second-harmonic generation in barium borate, the complex ring pattern induced by self-focusing due to the strong nonlinear interaction of the laser pulse in the pair of CdS crystals is filtered out using second-harmonic nonlinear crystal to recover a Gaussian shape spatial profile. We also present the temporal compression of the resulting 512 nm laser pulse up to 45 fs by using a pair of standard transmissive gratings, leading to a pulse compression factor of 6.13. This technique is compact, inexpensive, and robust and produces ultrafast optical pulses from an input laser pulse whose duration and energy range are generally incompatible with a straightforward compression method in nonlinear optical fibers.