Broadband vibrational sum-frequency generation spectrometer at 100 kHz in the 950-1750 cm$^{-1}$ spectral range utilizing a LiGaS$_{2}$ optical parametric amplifier

TL;DR

This paper introduces a high-speed, broadband vibrational sum-frequency generation spectrometer operating at 100 kHz in the 950-1750 cm$^{-1}$ range, utilizing a LiGaS$_{2}$ optical parametric amplifier for enhanced spectral analysis.

Contribution

The paper presents a novel 100 kHz VSFG spectrometer using a LiGaS$_{2}$ OPA, offering improved signal-to-noise ratio and cost-effectiveness over traditional methods.

Findings

Achieved high-resolution vibrational spectra of lipid monolayers.

Demonstrated low-noise, high-efficiency spectral acquisition.

Provided a compact, easy-to-use alternative to existing schemes.

Abstract

We present a 100 kHz broadband vibrational sum-frequency generation (VSFG) spectrometer operating in the 5.5-10.5 $\mu$m (950-1750 cm$^{-1}$) wavelength range. The mid-infrared beam of the system is obtained from a collinear, type-I LiGaS$_{2}$ crystal based optical parametric amplifier seeded by a supercontinuum and pumped directly by 180 fs, ~32 $\mu$J, 1.03 $\mu$m pulses from an Yb:KGd(WO$_{4}$)$_{2}$ laser system. Up to 0.5 $\mu$J mid-infrared pulses with durations below 100 fs were obtained after dispersion compensation utilizing bulk materials. We demonstrate the utility of the spectrometer by recording high-resolution, low-noise vibrational spectra of Langmuir-Blodgett supported lipid monolayers on CaF$_{2}$. The presented VSFG spectrometer scheme offers superior signal-to-noise ratios and constitutes a high-efficiency, low-cost, easy-to-use alternative to traditional schemes relying on optical parametric amplification followed by difference frequency generation.