Abstract
The emerging fiber-optic two-photon endomicroscopy technology holds a strong promise for enabling translational applications of nonlinear optical imaging. Effective femtosecond pulse dispersion management is critical for achieving high-quality imaging. Here we report systematic analyses and performance characterization of a dual-fiber spectro-temporal dispersion management scheme involving a grating pair as the pulse stretcher. Compared with conventional linear-only compensation, the grating-based spectro-temporal compensation also takes into account nonlinear effects and enhances the two-photon signal by ~3-fold as experimentally demonstrated. Numerical simulations were carried out to systematically investigate the influence of several key design parameters on the overall compensation efficacy. Furthermore, comprehensive performance comparison with an ideal grism-pair counterpart reveals that a grating-pair stretcher affords much higher power throughput and thus is preferable for portable endomicroscopy systems with limited laser source power.
Highlights
The emerging two-photon endomicroscopy technology is critical for translational clinical applications of nonlinear microscopy, and recent studies have demonstrated its strong promise to enable functional histological imaging of internal organs in vivo, in situ and in real time [1,2,3,4,5,6,7,8,9,10]
We have undertaken a comprehensive analyses and characterization of the dualfiber spectro-temporal dispersion compensation scheme with a grating pair serving as the pulse stretcher in the context of fiber-optic two-photon endomicroscopy imaging
The dispersion compensation efficacy of this setup was experimentally confirmed as enhancing the two-photon signal by ~3-fold compared with the linear-only single-fiber counterpart
Summary
The emerging two-photon endomicroscopy technology is critical for translational clinical applications of nonlinear microscopy, and recent studies have demonstrated its strong promise to enable functional histological imaging of internal organs in vivo, in situ and in real time [1,2,3,4,5,6,7,8,9,10]. Since two-photon excitation (2PE) efficiency scales reciprocally with the temporal pulsewidth [12], effective dispersion management is indispensable to fiber delivery of ultrafast laser pulses to the distal end of the endomicroscope. The negative pre-chirping GDD-compensation method always ends up with a narrowed spectral bandwidth, and temporal broadening is essentially inevitable as prescribed by the universal lower bound of time-bandwidth product [18] This explains previous observations that, starting with transform-limited 150 fs pulses, the best achievable pulsewidth out of an endomicroscope of an ~70 cm fiber length was on the order of ~400-500 fs FWHM [1,7,9]
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