Abstract-Covering the vibrational spectrum with microjoule mid-infrared supercontinuum pulses in nonlinear optical applications

Ashley M. Stingel, Heather Vanselous, and Poul B. Petersen

https://www.osapublishing.org/josab/abstract.cfm?uri=josab-34-6-1163

Nonlinear spectroscopies focused on molecular vibrations require high-energy [several microjoule (μJ)] laser pulses in the mid-infrared (IR). Current methods of generating μJ pulses in the mid-IR exhibit limited spectral coverage, while pulses that span the mid-IR range display insufficient pulse energies for nonlinear spectroscopy. Here we present the generation of high-energy mid-IR supercontinuum laser pulses by focusing 70 fs, 30 μJ mid-IR pulses in commercially available bulk chalcogenide glasses. The resulting supercontinuum pulses exhibit pulse energies of several μJ, which is sufficient for nonlinear spectroscopic applications, while spanning the important wavelength range from below 2.5 μm to over 10 μm at the 10% level (2.5–11 μm at −20  dB$-20\mathrm{dB}$)—more than two octaves within the mid-infrared. This facilitates capturing most of the fundamental transitions (𝑣=0→1$v=0\to 1$) of molecular vibrations in a wide range of applications including nonlinear experiments, as demonstrated with sum-frequency generation spectroscopy.

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