ИСТИНА

The technique of two-dimensional infrared (2D IR) Fourier spectroscopy using ultrashort pulses in the mid-infrared range is a modern technique for studying ultrafast dynamics in complex vibrational systems, 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 analysis of ultrafast chemical reactions involving complex molecular systems. Two-dimensional infrared spectroscopy provides more information compared to one-dimensional methods: it reveals the connections between interacting modes, observes the temporal evolution of the vibrational response spectrum, and determines the influence of the environment on the studied molecule [1-7]. In this work, we present a universal laser platform for broadband 2D spectroscopy using ultrashort mid-IR pulses. The laser system designed 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 μm. Broadband excitation and probing with pulses having such parameters, combined with heterodyne detection techniques and interferometric control of the time intervals between incoming pulses, open up opportunities for studying ultrafast dynamics of molecular coherence, as well as ultrafast kinetics of population and energy transfer between various degrees of freedom in a wide class of complex molecular systems. In the implemented scheme, the infrared signal is transferred to the visible range using a nonlinear optical process of sum-frequency generation with a chirped pulse at a center wavelength of 800 nm. This solution makes it possible to avoid the use of single-element MCT detectors for registering the signal. Instead, fast kilohertz silicon arrays that measure the entire range of interest in a single scan can be easily applied. Additional phase modulation of the pump pulses, achieved through an original device based on a galvanoscanning module, was used instead of amplitude modulation by an optical chopper in our 2D IR experiment to increase the signal-to-noise ratio and the scanning speed.