Spatial-spectral coupling in coherent anti-Stokes Raman scattering microscopy

Area of Science:

• Nonlinear optics
• Molecular spectroscopy
• Microscopy

Background:

• Coherent anti-Stokes Raman scattering (CARS) microscopy is a label-free technique for molecule-specific imaging.
• Spectral distortions arise from resonant and non-resonant term interference, necessitating retrieval algorithms.
• Spatial distortions, particularly due to the Gouy phase, occur for sub-Rayleigh range objects.

Purpose of the Study:

• To investigate the intrinsic coupling between focal position and spectral contributions in CARS image formation.
• To demonstrate that conventional retrieval methods are insufficient to correct these coupled distortions.

Main Methods:

• Analysis of third-order nonlinear optical processes in CARS microscopy.
• Theoretical consideration of Gouy phase effects on spatial imaging.
• Examination of the interplay between spectral and spatial information in image formation.

Main Results:

• Identified an intrinsic coupling between focal position and spectral contributions in nonlinear image formation.
• Demonstrated that spatial and spectral distortions are fundamentally linked.
• Showed that conventional spectral retrieval algorithms cannot correct these coupled effects.

Conclusions:

• The intrinsic coupling of focal position and spectral contributions presents a fundamental challenge in CARS microscopy.
• Existing retrieval methods are inadequate for correcting the observed spatial and spectral distortions.
• Further development of advanced imaging and correction strategies is required for accurate CARS hyperspectral imaging.