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

We report on a 100-kHz two-dimensional infrared (2DIR) spectrometer in the pump-probe geometry, which we apply to the measurement of the 2DIR spectrum of carboxyhemoglobin. The probe pulses are spectrally resolved by chirped-pulse upconversion (CPU) using a fast 2048-pixel line scan CMOS camera. The two-pulse pump sequence is generated using a conventional interferometer with a fast-scanning mechanical delay line allowing to achieve a scanning frequency of 2 Hz. The resulting modulation frequency of 3.1 kHz is large enough to shift the relevant signal away from the low-frequency noise of the laser source. The combined use of an interferometer on the pump side and of CPU on the probe side opens the way to an improved spectral resolution in both pump and probe dimensions, as compared to currently available 100-kHz 2DIR spectrometers based on pulse shapers and mercury-cadmium telluride detector arrays.