Fourier-transform coherent anti-Stokes Raman scattering microscopy

Area of Science:

• Optics and Photonics
• Microscopy Techniques
• Spectroscopy

Background:

• Coherent Anti-Stokes Raman Scattering (CARS) microscopy is a powerful vibrational imaging technique.
• Conventional CARS microscopy often suffers from nonresonant background interference, which can obscure weak resonant signals.
• Developing methods to suppress this background is crucial for enhancing CARS sensitivity and specificity.

Purpose of the Study:

• To introduce and validate a novel Fourier-transform-based implementation of CARS microscopy.
• To demonstrate the capability of time-resolving the CARS signal for background suppression.
• To achieve high-resolution, spectrally resolved vibrational imaging over a broad spectral range.

Main Methods:

• Utilized a single femtosecond laser source and a Michelson interferometer to generate two time-delayed pulse replicas.
• Integrated the pulsed laser system into a scanning multiphoton microscope.
• Employed Fourier-transform analysis by varying the time delay between the pulses to extract spectral information and remove nonresonant background.

Main Results:

• Successfully implemented a Fourier-transform-based CARS microscopy method.
• Demonstrated effective time-resolution of the CARS signal, enabling efficient nonresonant background removal.
• Obtained high-resolution, spectrally resolved images of CARS modes across approximately 1500 cm(-1) spectral bandwidth.
• Showcased the technique's efficacy by imaging polystyrene beads in a solvent.

Conclusions:

• The developed Fourier-transform CARS microscopy offers a robust approach for vibrational imaging.
• This method provides significant advantages in background suppression and spectral resolution.
• The technique is well-suited for high-quality imaging of various samples, including polymer microspheres.