Extended bandwidth wavelength swept laser source for high resolution optical frequency domain imaging

Area of Science:

• Optical Engineering
• Biomedical Imaging
• Laser Physics

Background:

• Achieving high axial resolution in optical frequency domain imaging (OFDI) is crucial for detailed tissue visualization.
• Wider bandwidth wavelength-swept lasers are key to improving axial resolution in OFDI systems.
• Existing laser technologies face limitations in tuning range and spectral stability.

Purpose of the Study:

• To develop a wide tuning range, all-fiber wavelength-swept laser for enhanced OFDI.
• To demonstrate a novel method for combining two laser cavities to achieve a broader scanning range.
• To validate the improved imaging performance in ex vivo and in vivo biological samples.

Main Methods:

• Designed and constructed an all-fiber laser system incorporating two coupled ring cavities.
• Utilized a single Fabry-Perot tunable filter shared between the two cavities, each with distinct semiconductor optical amplifiers.
• Employed amplifier modulation to achieve consecutive wavelength sweeps and fused them post-processing for a total scan range of 223 nm.

Main Results:

• Achieved a total scanning range of 223 nm centered at 1250 nm, enabling 3.3 µm axial resolution in air.
• Demonstrated improved image quality and reduced speckle size in OFDI tomograms.
• Successfully imaged swine esophagus ex vivo and human skin and nailbed in vivo.

Conclusions:

• The developed all-fiber wavelength-swept laser effectively broadens the scanning range for OFDI.
• This technology offers a significant improvement in axial resolution and image quality for biomedical applications.
• The system shows promise for in vivo and ex vivo imaging of biological tissues.