SELECTIVE EXCITATION OF COHERENT ANTI-STOKES RAMAN SCATTERING VIA PHASE STEP MODULATION

Abstract

It is known that femtosecond coherent anti-Stokes Raman scattering (CARS) method suffers from the drawback of poor selectivity between neighboring Raman energy levels due to the large bandwidth of the pulses. Quantum coherent control based on the ultrashort pulse shaping technique is a promising solution. In this paper, we propose a simple approach to realize the selective excitation of CARS spectra by shaping both the probe and pump pulses with the π phase step. By phase step modulation of the probe pulse, we show that the CARS signals between neighboring Raman energy levels can be greatly narrowed and differentiated, and then selective excitation can be realized by modulating both the probe and pump pulses. Finally, the mechanism of the selective excitation by population transfer is briefly discussed.