Abstract
Infrared pulses with large spectral width extending from 1.2 to 3.4 μm 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 μm and 65 fs duration. With 2.8 mJ input energy we obtained up to 700 μJ 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 χ2 nonlinearity of DAST, but the shape of the spectrum indicates that a delayed χ3 process may also be involved. Numerical simulations reproduce the experimental results qualitatively and provide an insight in the mechanisms underlying the asymmetric spectral broadening.
Highlights
Energetic broadband laser pulses in the short wavelength infrared region (SWIR, 1−3 μm) have attracted interest in the recent years due to their numerous applications ranging from high harmonic generation [1], multidimensional vibrational spectroscopy [2], and hyperspectral imaging in medicine [3] to solar cell inspection and imaging applications
We demonstrate that pumping the DAST crystal at 1.5 μm with the optimal pump fluence allows extending the spectrum towards infrared wavelengths up to 3.4 μm, limited by strong absorption in the organic material
Shown in figure 2 are the spectra generated in the DAST crystal pumped with different peak fluences
Summary
Energetic broadband laser pulses in the short wavelength infrared region (SWIR, 1−3 μm) have attracted interest in the recent years due to their numerous applications ranging from high harmonic generation [1], multidimensional vibrational spectroscopy [2], and hyperspectral imaging in medicine [3] to solar cell inspection and imaging applications. Two-cycle pulses with spectra ranging from 1.2 to 2.4 μm were recorded from DAST driven by a short SWIR pump [15]. Organic crystals have attracted large attention for their potential to generate several MV cm–1 single-cycle electric fields at THz frequencies by optical rectification [16,17,18]. In this context, moderate red-shift on the optical pump was observed in DSTMS
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