We demonstrate a highly multimodal nonlinear micro-endoscope for real-time, label-free imaging of biological tissues. The endoscope can perform two and three photon excited fluorescence, second, third harmonic and CARS imaging for different excitation wavelengths. Ultrashort pulses are delivered to the sample by a double-clad antiresonant hollow core fiber over the 800-1800 nm spectral band. The fiber tip is placed into a doubly resonant piezoelectric tube which allows a spiral scanning on the sample. The endoscope distal head containing the scanning device and the GRIN micro-objective is 1.5 mm in diameter and 35 mm long. Real-time nonlinear imaging at 10 frame/s is demonstrated.
We demonstrate 3-photon fluorescence micro-endoscopy using a negative curvature hollow core fiber and a 2.2 mm miniature scanning head. The fiber design allows distortion-less, delivery of <100 fs pulses without dispersion pre-compensation requirements. The fiber also features a double cladding allowing the back-collection of nonlinear signals through the same fiber. Sub-micron spatial resolution together with large field of view is made possible by the combination of a miniature distal objective lens with a functionnalization of the fiber output with a GRIN fiber spliced to the output facet. 3-photon fluoresence imaging is demonstrated on various biological samples.
We present a flexible, compact, 2photon, 3photon, SHG and CARS nonlinear endo-microscope featuring a 2.2 mm outer diameter and a length of 34 mm. It uses a negative curvature hollow-core double-clad fiber that is scanned with a resonant piezo-scanner. The fiber design allows distortion-less, background-free delivery of femtosecond and picosecond excitation pulses and the back-collection of nonlinear signals through the same fiber. Sub-micron spatial resolution together with >300 microns field of view is made possible using micro-lenses or GRIN based miniature objective lens. We demonstrate 2-photon and 3-photon fluorescence, SHG, THG and CARS imaging at a rate of 10 frames/s.
We present a flexible, compact, and multimodal nonlinear endoscope (2.2 mm outer diameter) based on a resonantly scanned negative curvature hollow-core double-clad fiber. The fiber design allows distortion-less, background-free delivery of femtosecond and picosecond excitation pulses and the back-collection of nonlinear signals through the same fiber. Sub-micron spatial resolution together with large field of view is made possible by the combination of a miniature objective lens together with a silica microsphere lens inserted into the fiber core. We demonstrate coherent anti-Stokes Raman scattering, 2-photon fluorescence and second harmonic generation imaging at a rate of 10 frames/s.
Non-linear optical microscopy proves to be an indispensable tool in natural sciences and becomes more and more attractive for clinical applications. Coherent Raman scattering, for instance, has the potential to become an in-vivo fast label-free histology tool as its chemical selectivity provides quantitative information on lipids and proteins locations and concentrations in tissues. Along with these techniques, second-harmonic generation of collagen and 2-photon excitation fluorescence broaden even more the non-linear imaging ability as collagen fibers represent an important role in human body construction. Whilst 2-photon excitation fluorescence allows to study auto-fluorescence (ex. NADH and NADHP molecules), and to excite a vast range of chromophores. However, absorption and scattering limit significantly the nonlinear imaging depth into tissues. As a solution, we offer a flexible, compact, and multimodal nonlinear endoscope (2.2 mm outer diameter, 35 mm rigid length) based on a resonantly piezo scanned hollow-core negative curvature double-clad fiber. The fiber design allows distortion-less, background-free delivery of femtosecond excitation pulses and the back-collection of nonlinear signals through the same fiber. The double-cladding of this fiber attends 10^5μm of silica collection surface which allows for a 4-fold collection improvement compared to previously used Kagomé hollow core fibers. Having a good control on the resonantly scanning fiber the endoscope can perform nonlinear imaging up to 8 frames per second over a field of view of 400μm. We demonstrate 2photon, SHG and CARS imaging in ex vivo gastric human tissue samples and in-vivo 2-photon fluorescence imaging of GFP-labeled neurons in mouse brain.
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