Fourier Domain Mode Locking (FDML): A new laser operating regime and applications for optical coherence tomography

Area of Science:

• Laser Physics
• Optical Engineering
• Biomedical Imaging

Background:

• Traditional laser operation methods face limitations in speed and tunability.
• Optical Coherence Tomography (OCT) requires fast and stable light sources for high-resolution imaging.

Purpose of the Study:

• To introduce and demonstrate Fourier Domain Mode Locking (FDML) as a novel technique for frequency-swept laser operation.
• To apply FDML lasers for advanced swept-source OCT imaging, enhancing speed and depth capabilities.

Main Methods:

• Developed an FDML laser using a long fiber ring cavity, semiconductor optical amplifier, and tunable fiber Fabry-Perot filter.
• Achieved effective sweep rates up to 290 kHz with a 105 nm tuning range at 1300 nm center wavelength.
• Integrated the FDML laser into a swept-source OCT system.

Main Results:

• Demonstrated FDML laser operation with high sweep rates and a broad tuning range.
• Achieved 108 dB sensitivity in OCT imaging with narrow dynamic linewidths, enabling imaging over a 7 mm depth.
• Reached OCT acquisition rates of up to 232,000 axial scans per second, enabling real-time 3D imaging.

Conclusions:

• FDML is a highly effective technique for generating high-speed frequency sweeps.
• FDML lasers are ideally suited for swept-source OCT, significantly improving imaging speed, depth, and sensitivity.
• This advancement paves the way for faster and more comprehensive biomedical imaging applications.