Abstract
We reported a record high power (>250 mW) and compact near-infrared fiber-optic femtosecond Cherenkov radiation source and its new application on nonlinear light microscopy for the first time (to our best knowledge). The high power femtosecond Cherenkov radiation was generated by 1.03 μm femtosecond pulses from a portable diode-pumped laser and a photonic crystal fiber as a compact, flexible, and highly efficient wavelength convertor. Sectioned nonlinear light microscopy images from mouse brain blood vessel network and rat tail tendon were then performed by the demonstrated light source. Due to the advantages of its high average output power (>250 mW), high pulse energy (>4 nJ), excellent wavelength conversion efficiency (>40%), compactness, simplicity in configuration, and turn-key operation, the demonstrated femtosecond Cherenkov radiation source could thus be widely applicable as an alternative excitation source to mode-locked Ti:Sapphire lasers for future clinical nonlinear microscopy or other applications requiring synchronized multi-wavelength light sources.
Highlights
Since its first demonstration, nonlinear light microscopy (NLM), including multi-photon fluorescence microscopy [1,2,3,4,5,6] and multi-harmonic generation microscopy [7,8,9], has attracted much biological and medical interest due to its capability to provide molecular and structural information with high 3D spatial resolutions
With their working wavelength located in the 0.65-1.1 μm, femtosecond Ti:Sapphire lasers with energetic multi-nJ output pulse energies and femtosecond output pulse durations are excellent excitation sources for twophoton fluorescence (TPF) imaging because two-photon absorption spectra in most common biomedical labeling fluorophores are centered between 0.7 μm and 1 μm window [4]
We have proposed and demonstrated a novel scheme of nonlinear microscopy by the fiber-optic femtosecond Cherenkov radiation (CR) with high conversion efficiencies and record high output power
Summary
Nonlinear light microscopy (NLM), including multi-photon fluorescence microscopy [1,2,3,4,5,6] and multi-harmonic generation microscopy [7,8,9], has attracted much biological and medical interest due to its capability to provide molecular and structural information with high 3D spatial resolutions. For future biomedical and clinical NLM applications requiring compact femtosecond source within the 0.7 to 1 μm window, an alternative light source to current mode-locked Ti: Sapphire laser can be implemented by combining a compact/portable/turnkey-operated femtosecond laser working outside the 0.7 to 1 μm window as pump and a proper PCF as an efficient/low-cost/-operated/direct-diode-pumped wavelength convertor. In the reported fiber-delivered light source with a wavelength down convertors to longer wavelength by the SSFS effect, Xu’s group has demonstrated a 1.7 μm frequency-shifted Raman soliton source by a high-power 1.55 μm Erbium-doped fiber laser and a large-mode PCF [3]. Due to the advantages of its excellent wavelength conversion efficiency (>40%), high average output power (>250 mW), wavelength tunability over 100 nm, compactness, simplicity, and turn-key operation, for NLM, the demonstrated femtosecond CR source could be widely applicable as an alternative of mode-locked Ti:Sapphire laser in many clinical, biomedical, industrial or other applications
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