Fiber four-wave mixing source for coherent anti-Stokes Raman scattering microscopy

Area of Science:

• Optics and Photonics
• Biomedical Imaging
• Laser Physics

Background:

• Coherent anti-Stokes Raman scattering (CARS) microscopy offers label-free vibrational imaging.
• Existing CARS light sources often face challenges with bulkiness, synchronization, and group-velocity mismatch.
• Picosecond pulsed lasers are crucial for achieving high peak power and efficient nonlinear processes in CARS.

Purpose of the Study:

• To develop a compact and robust fiber-format picosecond light source for CARS microscopy.
• To demonstrate efficient generation of synchronized, dual-color picosecond pulses using four-wave mixing.
• To validate the performance of the developed source for high-quality biological imaging.

Main Methods:

• Utilized a Yb-doped fiber amplifier to generate initial picosecond pulses.
• Employed four-wave mixing (FWM) in a normal-dispersion photonic crystal fiber for frequency conversion.
• Seeded the FWM process to mitigate group-velocity mismatch and enhance conversion efficiency.
• Tuned the output wavelength from 775 to 815 nm with power exceeding 160 mW.

Main Results:

• Successfully generated a synchronized two-color picosecond pulse train via FWM.
• Demonstrated efficient frequency conversion into narrow spectral bands by seeding the FWM process.
• Achieved nearly transform-limited pulses with tunable output wavelengths.
• Obtained high-quality CARS images of animal tissues and cells.

Conclusions:

• The fiber-format picosecond light source is a viable and efficient tool for CARS microscopy.
• Seeding the FWM process effectively overcomes group-velocity mismatch challenges.
• The developed source enables high-resolution, label-free imaging of biological samples.