ИСТИНА

The technique of two-dimensional infrared (2D IR) Fourier spectroscopy using ultrashort pulses of the mid-infrared range is a modern method for studying ultrafast dynamics in complex oscillatory systems, which is based on the nonlinear four-wave interaction of pulsed broadband infrared radiation with matter [1–7]. Femtosecond temporal resolution, combined with spectral selectivity and high spatial resolution, make it possible to use two-dimensional infrared spectroscopy for characterization of rapidly interconverting substances and recording ultrafast processes in complex biological and chemical systems. Two-dimensional infrared spectroscopy makes it possible to obtain more information compared with one-dimensional techniques: to reveal the relationship between interacting modes, observe the temporal evolution of vibrational frequencies, determine the influence of the environment on the behavior of individual elements in complex complexes and in solutions [1–7]. In this work, we present a universal laser platform for broadband 2D spectroscopy using ultrashort mid-IR pulses. The laser system developed for 2D spectroscopy generates radiation pulses with a duration of less than 70 fs and a wavelength tunable in the range of 2.6 – 10 mm. Broadband excitation and probing by pulses with such parameters, in combination with the heterodyne detection technique implemented in the mid-IR range, open up possibilities for studying ultrafast dynamics of molecular coherence, as well as ultrafast population kinetics and energy exchange between different degrees of freedom in a wide class of complex molecular systems. Implemented chirped-pulse up-conversion method enables the detection of mid-infrared spectra at a much higher framerate using a 1 kHz silicon CCD camera by sum-frequency mixing a mid-IR field with a highly chirped near-IR (800 nm) field. Additional quasi-phase-cycling achieved by sub-cycle delay modulation of pump pulses with original device, based on galvo-scanning head, was used to replace optical chopping in our 2D IR experiment in order to enhance the signal size, and, at the same time, eliminate scattering contamination. The work was supported by the Russian Science Foundation with grant No. 22-12-00149