Chirped-pulse adiabatic control in coherent anti-Stokes Raman scattering for imaging of biological structure and dynamics

Abstract

Two novel control methods based on adiabatic passage are proposed to be implemented in coherent anti-Stokes Raman scattering (CARS) microscopy for noninvasive imaging of biological structure and dynamics. The first method provides optimal pulse-area control of the resonant vibrational transitions by using a pair of equally linear-chirped pulses. The second method, named the 'roof' method, utilizes the chirp sign variation at the central time and gives robust adiabatic excitation of the resonant vibrational mode. Both methods are robust with respect to suppression of the off-resonant transitions. The methods allow one to achieve chemical sensitivity with high resolution and can be used to obtain CARS spectra of biological molecules with efficiently suppressed background.

Creating maximum coherence using chirped pulses without adiabatic elimination of excited states

“…[6] . Figure 3 shows the results of the roof method implementation without the elimination of the excited state.…”

“…The results of numerical simulation obtained without making the adiabatic elimination of the excited electronic state show the robustness of the roof method. [6] Dressed state representation analysis is used to explain the dependence of the CARS coherence on the twophoton detuning. Presented results show that the requirement of the strong pulse intensities to implement the roof method can be relaxed while preserving the attractive robustness of the scheme.…”

Picosecond time scale modification of forward scattered light induced by absorption inside particles

“…In order to carry out such investigation, model systems made up of spherical particles in suspension in a host medium have been widely studied [1,2]. Femtosecond lasers are bright enough to go through very thick media with tunable wavelength [3,4], and are used in a wide variety of optical diagnosis and imaging techniques (SHG [5], THG [6], CARS [7], …). Furthermore, thanks to Optical Kerr Gate (OKG) measurements [8] or up-conversion technique [9], it is possible to temporally sample the light going out of the sample with a resolution of approximately 100 fs [10] (i.e.…”

Robust control by two chirped pulse trains in the presence of decoherence

“…21 and does not change further on. The adiabatic passage takes place in both TLSs and results in zero coherence 34 in the detuned, j3iÀj4i TLS and maximum coherence 12 in the resonant, j1iÀj2i TLS in a wide range of the field parameters satisfying condition ' 1/, see also [9]. The pump and Stokes pulses are described by the Wigner diagrams in Figure 2.…”

“…Field parameters are I ¼ 28.4 Â 10 12 W cm À2 , 0 ¼ 177 fs, 0 s ¼ 2:8 Â 10 À4 cm À2 , giving ¼ 1.58 ps. These parameters of the fields are chosen in accordance with the data published in [9] to provide the adiabatic passage in the TLSs resulting in a maximum value of 12 and zero 34 . The parameters that determine decoherence 2 and À vary in the region from 0 to 0.085 THz, giving the time of vibrational energy relaxation and collisional dephasing to change from infinity to 11.76 ps.…”