Generation of High Power Infrared Short Pulse by Cr:Forsterite and Development of Two-Dimensional Vibrational Spectroscopy

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We have developed high power, infrared (IR) short pulse and third order optical nonlinear spectroscopy in the infrared region using the IR pulse. The infrared pulses are generated by some optical nonlinear processes such as difference frequency mixing and optical parametric generation/amplification with an all-solid-state laser. Group velocity dispersion in the pulse is compensated by inserting a silicon plate in the optical path. The pulse width is measured to be 55 fs with an energy of more than microJ/pulse by an autocorrelation method, which is the shortest pulse of the infrared pulse with such a high energy to our knowledge. Using this pulse we have constructed optical systems of nonlinear spectroscopy such as time-integrated and frequency-resolved transient grating, time-integrated and frequency-resolved 2- and 3-pulse photon echo. These techniques are multi-dimensional methods in time and/or frequency, and the frequency-resolved 3-pulse photon echo is a homodyne detected vibrational version of 2D NMR. We have applied these techniques to several vibrational modes such as three-atom ions (OCN^- and SCN^-) in polar solvents, the -N=C=N- anti-stretching modes of large organic molecules, the C=O stretching modes of metal porphyrines, the CN stretching modes of cyano-iron complexes, and the OH stretching mode of hydrogen bonding liquids. We discuss vibrational dynamics of these modes including vibrational population relaxation, pure vibrational dephasing, dynamical fluctuation and spectral diffusion, inhomogeneity of the transition frequency, and so on.