Mode Selective Excitation Using CoherentControl Spectroscopy

摘要

Femtosecond time-resolved coherent anti-Stokes Raman scattering (fs-CARS) givesaccess to ultrafast molecular dynamics. However, femtosecond laser pulses are spectrally broadand therefore coherently excite several molecular modes. While the temporal resolution is high,usually no mode-selective excitation is possible. This paper demonstrates the feasibility ofselectively exciting specific molecular vibrations in solution phase with shaped fs laserexcitation using a feedback-controlled optimization technique guided by an evolutionaryalgorithm. This approach is also used to obtain molecule-specific CARS spectra from a mixtureof different substances. The optimized phase structures of the fs pulses are characterized to getinsight into the control process. Possible applications of the spectrum control are discussed.