Abstract

Nonlinear optics has been at the heart of modern imaging and detection techniques that require measurements with high spectral selectivity. Coherent anti-Stokes Raman scattering belongs to one of the frontiers of nonlinear optics methods having broad applications in chemistry, medicine and environmental sciences. A principal task for advancing CARS techniques is to be able to distinguish between related species having vibrational frequency differences within a fraction of a wave number and to register a coherent signal from traces of molecules. That is where quantum control proved to be useful through the active phase-amplitude shaping of laser pulses to maximize CARS signal. We will discuss new approaches for ultrafast pulse shaping that significuntly enhance CARS signal and suppress the background. They are designed to create the maximum vibrational coherence in a predetermined molecular fragment by making use of the linear chirp of the pump and Stokes pulses [1, 2], Fig.1. The proposed pulse shaping was realized experimentally, Fig.2. We have analyzed the impact of spontaneous decay and collisional dephasing on controllability [3] and showed that high coherence in a desired vibration can be sustained by two chirped pulse trains with the pulse repetition rate close to spontaneous decay rate. Also, we investigated the impact of the coupling between vibrational modes on controllability of selective excitation of Raman active vibrational modes [4].

© 2016 Optical Society of America