Two-dimensional infrared spectroscopy using a fast-scanning interferometer and chirped pulse upconversion at 100 kHz.

This article focuses on the development and demonstration of a 100-kHz two-dimensional infrared (2DIR) spectrometer operating in the pump–probe geometry, which employs a fast-scanning interferometer to generate the two-pulse pump sequence and chirped-pulse upconversion (CPU) combined with a fast CMOS camera for probe detection. This approach achieves a spectral resolution of about 2 cm⁻¹ in both pump and probe dimensions and is applied to measure the 2DIR spectrum of carboxyhemoglobin near the carbon-monoxide stretching mode. The method offers improved spectral resolution and affordability compared to existing 100-kHz 2DIR spectrometers based on pulse shapers and mercury–cadmium telluride detector arrays, while effectively suppressing noise and coherent-scattering artifacts through dithering techniques. The results demonstrate spectral diffusion in the protein structure and suggest potential for further enhancements in spectral resolution and spectral coverage.