Deep-tissue two-photon brain imaging enabled by a tunable fiber-optic dispersive wave generator

Area of Science:

• Biomedical Optics
• Ultrafast Laser Technology
• Neuroimaging

Background:

• Two-photon imaging offers high resolution for deep-tissue visualization.
• Generating tunable, high-energy ultrashort pulses is crucial for advanced imaging techniques.
• Existing methods often face limitations in efficiency and tunability.

Purpose of the Study:

• To develop a novel fiber-optic dispersive wave generator.
• To achieve highly efficient, wavelength-tunable ultrashort pulse generation.
• To enable multicolor deep-tissue two-photon imaging of neuronal and vascular structures.

Main Methods:

• Utilized a compact Yb: fiber laser-driven system.
• Employed precisely parameter- and phase-matching-controlled dispersive wave generation in photonic crystal fiber.
• Guided system construction with comprehensive numerical simulations.

Main Results:

• Generated sub-100 fs pulses with over 6.7 nJ energy.
• Achieved a continuously tunable spectral range of 880-950 nm.
• Attained a record-high optical conversion efficiency of up to 65%.

Conclusions:

• The developed system enables high-resolution structural imaging in mouse brain at depths exceeding 450 μm.
• Optimized output for two-photon excitation of common fluorescent proteins.
• Represents a significant advancement in ultrafast fiber laser technology for biomedical imaging.