Abstract
Optical sources in the visible region immediately adjacent to the near-infrared biological optical window are preferred in imaging techniques such as spectroscopic optical coherence tomography of endogenous absorptive molecules and two-photon fluorescence microscopy of intrinsic fluorophores. However, existing sources based on fiber supercontinuum generation are known to have high relative intensity noise and low spectral coherence, which may degrade imaging performance. Here we compare the optical noise and pulse compressibility of three high-power fiber Cherenkov radiation sources developed recently, and evaluate their potential to replace the existing supercontinuum sources in these imaging techniques.
Highlights
The lack of molecular contrast in standard optical coherence tomography (OCT) can be overcome by the spectroscopic OCT technique that is sensitive to optical absorption [1]
Because the intrinsic relative intensity noise (RIN) of the SC from photonic crystal fibers [4] is known to degrade the OCT signal-to-noise ratio (SNR) [5], a natural question arises whether a low-noise alternative source is available
A seemingly independent but closely related situation is encountered in two-photon fluorescence microscopy (TPF), another widespread three-dimensional imaging technology with better spatial resolution but smaller fields-of-view
Summary
The lack of molecular contrast in standard optical coherence tomography (OCT) can be overcome by the spectroscopic OCT technique that is sensitive to optical absorption [1]. The absorption of endogenous molecules in biological samples occurs predominantly in the visible region (400-700 nm), not the near-infrared region (700-1400 nm) typically used in OCT, leading to the low sensitivity/contrast of these molecules. Because most fluorophores native to biological samples can only be (efficiently) two-photon excited around or below 700 nm [6], visible ultrafast pulses are often advantageous over conventional Ti:sapphire laser pulses (700-1000 nm) in label-free TPF applications such as cancer diagnostics and in vivo imaging. To avoid the expensive and bulky OPO, other studies developed customized fs-pulse-induced SC sources and filtered out the visible portion to image tryptophan [8] and hemoglobin [9]. CR-LaserQuantum [11] Ti:Sa (Taccor s, Laser Quantum) 800 nm ~15 fs (chirped) 1.000 GHz NL-2.0745-02 2.0 μm 745 nm 9 cm 143 104 used
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