Optimization of frequency-doubled Er-doped fiber laser for miniature multiphoton endoscopy

Abstract

Frequency-doubled femtosecond Er-doped fiber laser is a low-cost and portable excitation source suitable for multiphoton endoscopy. The frequency-doubled wavelength at 780 nm is used to excite the intrinsic fluorescence signal. The frequency-doubling with a periodically poled MgO∶LiNbO 3 (PPLN) is integrated in the distal end of the imaging head to achieve fiber connection. The imaging speed is further improved by optimizing the excitation laser source. A 0.3-mm length of PPLN crystal is selected and the Er-doped fiber laser is manipulated to match its bandwidth with the acceptance bandwidth of the PPLN. Through this optimization, a reduced pulsewidth of 80 fs of the frequency-doubled pulse is achieved. All-fiber dispersion compensation and pulse compression by single mode fiber is conducted, which makes the fiber laser directly fiber-coupled to the imaging head. An imaging speed of 4 frames∕s is demonstrated on ex vivo imaging of unstained biological tissues, which is 10 times faster than our previous study using a 1-mm-long PPLN. The results show that miniature multiphoton endoscopy using frequency-doubled Er-doped fiber laser has great potential for clinical applications. © The Authors.Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Simultaneous 2-photon and 3-photon multimodal signal acquisition for multiphoton microscopy

“…2(b), the measured SHG and THG peak wavelength is slightly off their theoretical value of 790/2 nm and 1580/3 nm, respectively. This is considered due to that the excitation beams are broadband sources with a -10 dB bandwidth of >100 nm and >25 nm for the ~1580-and ~790-nm laser beams, respectively [15]. In addition, rather than an ideal Gaussian distribution, the spectrum distributions of both wavelengths are complicated with detailed structures (this is common and typical for fiber-based mode-locked lasers) [15].…”

“…This is considered due to that the excitation beams are broadband sources with a -10 dB bandwidth of >100 nm and >25 nm for the ~1580-and ~790-nm laser beams, respectively [15]. In addition, rather than an ideal Gaussian distribution, the spectrum distributions of both wavelengths are complicated with detailed structures (this is common and typical for fiber-based mode-locked lasers) [15]. Based on these factors, an optimal reflective band for the notch dichroic beam splitter DBS3 is considered to be ~520±16 nm.…”

Stem Cell Therapy for Post-Traumatic Stress Disorder: A Novel Therapeutic Approach

“…This surge in clinical trials has led to the formation of regulations and guidelines for the use of stem cells in treating various neurological disorders [ 20 , 21 ]. Stem cell therapies provide benefit through various mechanisms in the CNS such as replacement of cells, modulating the inflammatory response, and providing neuroprotection [ 22 , 23 , 24 ]. These mechanisms vary depending on the source of stem cells.…”

Miniaturized multimodal multiphoton microscope for simultaneous two-photon and three-photon imaging with a dual-wavelength Er-doped fiber laser

“…The pulsewidth is 80 fs for both the 790-nm and 1580-nm pulses. The short pulsewidth is achieved by using a piece of SMF to compensate the dispersion in the EDF laser system [23]. A −10 dB bandwidth is characterized due to the multiple-peak structure in the spectrum.…”

“…In this paper, we will address those challenges. In our previous publications [22,23], we have reported a miniature 2PM system using a frequency-doubled EDF laser. In those papers, only the 790 nm beam was utilized while the residual 1580 nm beam was discarded.…”