Two-photon fluorescence microscope with a hollow-core photonic crystal fiber

Abstract

Since the first demonstration in 1990, two-photon fluorescence microscopy (TPFM) has made a great impact on biomedical researches. With its high penetration ability, low out-of-focus photodamage, and intrinsic three-dimensional (3D) sectioning capability, TPFM has been widely applied to various medical diagnosis and genome researches. Recently, single-mode optical fibers were introduced into the TPFM systems for remote optical pulse delivery. Fiberbased TPFM has advantages including isolating the vibration from laser and electronic devices, flexible system design, and low cross-talks. It is also the first step toward an all-fiber based two-photon endoscope. However, due to serious temporal broadening when conventional Ti:sapphire based femtosecond pulses propagate through the fiber, the twophoton excitation efficiency of the fiber-optic TPFM is much lower than the conventional one. The temporal broadening effect mainly comes from group velocity dispersion (GVD) and self-phase modulation (SPM), which also leads to significant spectral broadening. To reduce the temporal broadening effect, here we present a hollow-core photonic-bandgap fiber based TPFM. By replacing the conventional single-mode fiber with the hollow core photonic bandgap fiber, the GVD and SPM effects can be greatly reduced for high intensity, ultra-short pulse delivery. Femtosecond Ti:sapphire pulses passing through the fiber with negligible GVD and SPM effects is demonstrated in this paper. Much improvement of two-photon fluorescence excitation efficiency is thus achieved with the hollow-core photonic-bandgap fiber based TPFM.

Ultrafast optical pulse delivery with fibers for nonlinear microscopy

“…PCF has various potential applications in nonlinear microscopy imaging and telecommunications areas, since it has better optical characteristics than TIR-based optical fibers in terms of guiding, dispersion, and refraction (Lourtioz, 2005). It has been shown that the dispersion of ultrafast optical pulses can be significantly reduced by using photonic crystal fibers (Gobel and others, 2004; Kim and others, 2005; McConnell and Riis, 2004; Tai and others, 2004). Importantly, photonic crystal fibers also offer better performance than traditional fibers in conducting high power ultrafast optical pulses.…”

Optical biopsy in high-speed handheld miniaturized multifocal multiphoton microscopy

“…We observe minimal pulse broadening from 750 to 800 nm with 100 fs pulse width input. However, some prior studies [13][14] indicate that pulse broadening is closely related to GVD and is quite large in the similar range of wavelength for hollow core photonic bandgap crystal fiber but using an input pulse width of 200 fs. Therefore, the pulse propagation equation should be examined in detail in order to explain the discrepancy between these studies.…”

Long-period gratings in photonic crystal fiber: fabrication, characterization, and potential applications for gas sensing

“…7,8 PCFs can be made with parameters impossible to achieve in standard fibers, which has led some researchers and investigators to suggest that PCFs could become the ultimate transmission waveguide for electromagnetic fields. 9 As long as PCFs fulfill their potentials, they could have important applications in spectroscopy, 10 metrology, 11 biomedicine, 12 imaging, 13 optical coherence tomography (OCT), 14 sensing, [15][16][17][18] and telecommunications. [19][20][21][22][23] On the other hand, although long-period gratings (LPGs) has emerged at the same time as PCFs, 24 the fabrications of PCF-based fiber components have attracted great attention in resent years.…”