Multimodal coherent anti-Stokes Raman spectroscopic imaging with a fiber optical parametric oscillator

Area of Science:

• Biomedical Optics
• Neuroimaging
• Microscopy Techniques

Background:

• Multimodal imaging offers complementary information for biological samples.
• Coherent anti-Stokes Raman scattering (CARS) microscopy provides label-free contrast for specific molecular bonds.
• Two-photon excitation fluorescence (TPEF) microscopy allows for sensitive imaging of labeled structures.

Purpose of the Study:

• To develop a rapid, multimodal imaging system for simultaneous CARS and TPEF microscopy.
• To demonstrate the system's capability for high-speed imaging of neural tissue structures.

Main Methods:

• Utilized a femtosecond fiber laser coupled with a photonic crystal fiber (PCF)-based optical parametric oscillator (FOPO).
• Employed two PCFs with different zero dispersion wavelengths to achieve a tunable signal beam (840–930 nm).
• Integrated CARS imaging of myelin sheaths with TPEF imaging of labeled axons in rat spinal cord.

Main Results:

• Achieved simultaneous CARS and TPEF imaging with a pixel dwell time of 20 μs.
• Demonstrated the system's ability to visualize both unlabeled myelin and labeled axons in rat spinal cord tissue.
• Tuned the FOPO signal beam across a spectral range of 840–930 nm.

Conclusions:

• The developed multimodal imaging system enables fast, simultaneous visualization of different neural tissue components.
• This technique offers a powerful tool for studying neural structure and function with high spatiotemporal resolution.
• The tunable FOPO source enhances the versatility of CARS microscopy for various biological applications.