High Order Symmetry Structural Properties of Vibrational Resonances Using Multiple-Field Polarization Coherent Anti-Stokes Raman Spectroscopy Microscopy

Abstract

Polarization-resolved coherent anti-Stokes Raman scattering (CARS) is usually applied to measure the depolarization ratio in solutions or evidence orientation effects in anisotropic media. We present an extensive approach based on multiple-field polarization-resolved CARS, in order to unravel the complexity of vibrational resonances up to the fourth-order symmetry, at the microscopic scale in nonisotropic media. The CARS polarized signals measured under a continuous variation of the incident pump and/or Stokes excitation beams are analyzed using a full tensorial picture both in the nonresonant and resonant regimes. This method evidences the strong influence of vibrational symmetries on polarized CARS, and more specifically the occurrence of Kleinman symmetry deviations at the vicinity of the Raman lines frequencies. This technique, illustrated on a cubic symmetry crystal, is general and can be applied to other medium symmetries.

High-speed polarization-resolved coherent Raman scattering imaging

“…Note that hyperspectral analyses require disentangling the content of complex molecular bond mixtures. In this context, the modulation signals measured in this work can be interpreted into orientation distribution of vibrational bonds provided their symmetry is known, using microscopic to macroscopic frame transformations as detailed in [15,39].…”

“…1(c)]. Using such methods, high molecular organization has been evidenced in water molecules between phospholipid layers [11], CN bonds of liquid crystals [12,13], CH bonds of polyglucan chains in cellulose [14], and in various symmetry modes of zeolite crystals [15]. Monitoring the CH 2 vibrational stretching bond in lipids has shown considerable level of information on lipid order within artificial multilayers [16,17], where the measured modulation was used to retrieve quantitative information on sub-diffraction molecular orientational order behaviors, in particular, its mean orientation and angular distribution shape [17].…”

Multimodal nonlinear optical microscopy

“…Other promising directions include label-free imaging of organogenesis and drug delivery. Notably, the polarization sensitivity of CARS provides additional structural information and has been utilized to study molecular orientations in myelin [114, 203], single lipid bilayer [204], cellulose fiber [110], and crystal of pure fourth-order symmetry [205]. …”

Fast and label-free

“…The development of such SRS endoscopes is at an early stage 4,5 as they must deliver ultrashort pulses down optical fibres -a task made difficult by the spurious nonlinear interactions that take place in fibres, which can significantly alter the properties of the propagating pulses. Other anticipated applications are in the field of chemical compound sensing in soft matter and materials sciences, in which polarizationresolved stimulated Raman techniques are expected to provide images that are chemically specific but also bring structural or conformational information 6,7 . The demonstration by Ozeki et al that label-free, molecular-specific images can be generated at video rates paves the way towards these exciting developments.…”