Generation of 1.5-octave intense infrared pulses by nonlinear interactions in DAST crystal

TL;DR

This paper demonstrates the generation of broad, intense infrared pulses spanning 1.2 to 3.4 micrometers using nonlinear interactions in DAST crystals, with potential for scalable energy output.

Contribution

It introduces a method for generating ultra-broadband infrared pulses in DAST crystals, highlighting cascaded second-order nonlinear processes and potential for energy scaling.

Findings

Achieved 700 μJ pulses with 1.5 μm input and 65 fs duration.

Spectral broadening up to 3.4 μm confirmed experimentally.

Numerical simulations support the cascaded nonlinear process explanation.

Abstract

Infrared pulses with large spectral width extending from 1.2 to 3.4 um are generated in the organic crystal DAST (4-N, N-dimethylamino-4-N-methylstilbazolium tosylate). The input pulse has a central wavelength of 1.5 um and 65 fs duration. With 2.8 mJ input energy we obtained up to 700 uJ in the broadened spectrum. The output can be easily scaled up in energy by increasing the crystal size together with the energy and the beam size of the pump. The ultra-broad spectrum is ascribed to cascaded second order processes mediated by the exceptionally large effective chi2 nonlinearity of DAST, but the shape of the spectrum indicates that a delayed chi3 process may also be involved. Numerical simulations reproduce the experimental results qualitatively and provide an insight in the mechanisms underlying the asymmetric spectral broadening.