Measuring molecular order and orientation using coherent anti-stokes Raman scattering microscopy

Area of Science:

• Nonlinear optics
• Vibrational spectroscopy
• Microscopy

Background:

• Coherent anti-Stokes Raman scattering (CARS) microscopy is a rapidly advancing nonlinear vibrational imaging technique.
• It offers significant signal enhancement over spontaneous Raman scattering.
• CARS microscopy does not require exogenous labeling of specimens, preserving native sample states.

Purpose of the Study:

• To provide a theoretical description of Coherent anti-Stokes Raman scattering microscopy.
• To discuss the two primary operational modes: picosecond and multiplex CARS.
• To demonstrate the technique's potential through direct measurements of lipid structures.

Main Methods:

• Theoretical framework of CARS microscopy.
• Operational principles of picosecond CARS.
• Operational principles of multiplex CARS.

Main Results:

• Demonstration of label-free imaging of chemical composition and physical state.
• Direct measurement of acyl chain order in lipid monolayers, bilayers, and vesicles.
• Direct measurement of acyl chain orientation in lipid monolayers, bilayers, and vesicles.

Conclusions:

• Coherent anti-Stokes Raman scattering microscopy is a versatile and powerful tool for analyzing complex biological and material samples.
• The technique provides detailed insights into molecular structure and organization without labeling.
• CARS microscopy holds significant potential for applications across biophysics, biology, and materials science.