Compact fs ytterbium fiber laser at 1010 nm for biomedical applications

Abstract

Ytterbium-doped fiber lasers (YDFLs) working in the near-infrared (NIR) spectral window and capable of high-power operation are popular in recent years. They have been broadly used in a variety of scientific and industrial research areas, including light bullet generation, optical frequency comb formation, materials fabrication, free-space laser communication, and biomedical diagnostics as well. The growing interest in YDFLs has also been cultivated for the generation of high-power femtosecond (fs) pulses. Unfortunately, the operating wavelengths of fs YDFLs have mostly been confined to two spectral bands, i.e., 970-980 nm through the three-level energy transition and 1030-1100 nm through the quasi three-level energy transition, leading to a spectral gap (990-1020 nm) in between, which is attributed to an intrinsically weak gain in this wavelength range. Here we demonstrate a highpower mode-locked fs YDFL operating at 1010 nm, which is accomplished in a compact and cost-effective package. It exhibits superior performance in terms of both short-term and longterm stability, i.e., <0.3% (peak intensity over 2.4 μs) and <4.0% (average power over 24 hours), respectively. To illustrate the practical applications, it is subsequently employed as a versatile fs laser for high-quality nonlinear imaging of biological samples, including twophoton excited fluorescence microscopy of mouse kidney and brain sections, as well as polarization-sensitive second-harmonic generation microscopy of potato starch granules and mouse tail muscle. It is anticipated that these efforts will largely extend the capability of fs YDFLs which is continuously tunable over 970-1100 nm wavelength range for wideband hyperspectral operations, serving as a promising complement to the gold-standard Ti:sapphire fs lasers.

Non-Diffracting Light Wave: Fundamentals and Biomedical Applications

“…Traditional TPM scans the diffraction-limited spot across the sample. TPM performs better than traditional confocal microscopy in combating scattering and increasing the penetration, resulting from nonlinear excitation and longer wavelength illumination [121,128]. In order to image the volumetric information, the excitation light has to be scanned in three dimensions to traverse the sample structure.…”

Multiscale and Multimodal Optical Imaging of the Ultrastructure of Human Liver Biopsies

“…The focal intensities were set for the Stokes beam (1032 nm) at 16.5 mW and for the pump beam (799.3 nm) at 33 mW, respectively. For second harmonic generation (SHG) imaging the laser source was switched to a home-built fiber-based femtosecond laser with 400 fs pulse length (55MHz repetition rate) (described in Kong et al, 2017 ) operating at 1054 nm using 20 mW focal intensity while the filter set was changed to a bandpass at 532/18 nm and the 950 SP as well as two times the 785 SP to isolate the SHG signal.…”

Narrow Linewidth 49 W All Fiber Linearly Polarized Picosecond Laser Operating at 1016 nm

“…he ytterbium-doped fiber (YDF) lasers at short wavelength below 1020 nm (also called as S band) have many potential applications, such as a pump source for lasers and amplifiers [1][2], producing visible light by frequency doubling [3], producing deep-ultraviolet light for laser cooling of mercury atoms by frequency quadrupling [4,5], and nonlinear imaging of biological samples [6]. However, the absorption and emission characteristics of ytterbium ions make it difficult for YDF lasers to operate below 1020 nm, because the emission cross section at 1000-1020 nm is much smaller than 1030 nm and the absorption cross-section increases as wavelength decreases at this wavelength band.…”