All-fiber three-wavelength laser for functional photoacoustic microscopy

Area of Science:

• Biomedical Optics
• Laser Physics
• Medical Imaging

Background:

• Multi-wavelength pulsed lasers are crucial for functional optical-resolution photoacoustic microscopy (OR-PAM).
• Stimulated Raman scattering (SRS) offers a cost-effective method for generating multiple wavelengths from a single pump laser.
• Existing SRS laser systems often rely on free-space optics, leading to alignment instability and high maintenance.

Purpose of the Study:

• To develop a stable, all-fiber three-wavelength SRS laser source for functional OR-PAM.
• To simplify the alignment and improve the robustness of multi-wavelength laser generation for OR-PAM.
• To demonstrate the system's capability for long-term functional brain imaging.

Main Methods:

• An all-fiber network was designed to split, delay, and merge laser pulses, generating different wavelengths via SRS within fiber branches.
• A decoding algorithm was employed to separate photoacoustic signals from distinct wavelengths.
• The system was used to monitor brain function over a four-hour period.

Main Results:

• The all-fiber SRS laser source demonstrated stable energy ratios between wavelengths during prolonged operation.
• The system successfully separated photoacoustic signals and enabled calculation of oxygen saturation (sO2) and flow speed.
• Functional brain imaging over four hours showed exceptional stability.

Conclusions:

• The developed all-fiber SRS laser provides a stable, simplified, and cost-effective solution for functional OR-PAM.
• The system's robustness and stability are suitable for long-term preclinical and clinical applications.
• This technology enhances the feasibility of advanced OR-PAM for various biomedical imaging needs.