Dynamic gain driven mode-locking in GHz fiber laser.

Ultrafast lasers have become powerful tools in various fields, and increasing their fundamental repetition rates to the gigahertz (GHz) level holds great potential for frontier scientific and industrial applications. Among various schemes, passive mode-locking in ultrashort-cavity fiber laser is promising for generating GHz ultrashort pulses (typically solitons), for its simplicity and robustness. However, its pulse energy is far lower than the critical value of the existing theory, leading to open questions on the mode-locking mechanism of GHz fiber lasers.

Behavioral dynamics of neuroprotective macrophage polarization in neuropathic pain observed by GHz femtosecond laser two-photon excitation microscopy.

Macrophage polarization in neurotoxic (M1) or neuroprotective (M2) phenotypes is known to play a significant role in neuropathic pain, but its behavioral dynamics and underlying mechanism remain largely unknown. Two-photon excitation microscopy (2PEM) is a promising functional imaging tool for investigating the mechanism of cellular behavior, as using near-infrared excitation wavelengths is less subjected to light scattering. However, the higher-order photobleaching effect in 2PEM can seriously hamper its applications to long-term live-cell studies.

Occurrence, distribution, and translocation of legacy and current-use pesticides in pomelo orchards in South China.

Pomelo (Citrus grandis) is a highly popular and juicy member of the citrus family. However, little is known regarding the occurrence and distribution of pesticides in pomelo. In this study, we determined the levels of legacy (n = 25) and current-use pesticides (n = 2) in all parts of pomelo (i.

Unveiling the complexity of spatiotemporal soliton molecules in real time.

Observing the dynamics of 3D soliton molecules can hold great opportunities for unveiling the mechanism of molecular complexity and other nonlinear problems. In spite of this fantastic potential, real-time visualization of their dynamics occurring on femtosecond-to-picosecond time scales is still challenging, particularly when high-spatiotemporal-resolution and long-term observation are required. In this work, we observe the real-time speckle-resolved spectral-temporal dynamics of 3D soliton molecules for a long time interval using multispeckle spectral-temporal measurement technology.

A Pilot Nationwide Survey on the Concentrations of Neonicotinoids and Their Metabolites in Indoor Dust from China: Application for Human Exposure.

The present study assessed the residue levels of six parent neonicotinoids (p-NEOs) and four metabolites (m-NEOs) in indoor dust collected from 12 cities of China. Acetamiprid (ACE) and imidacloprid (IMI) were the predominated p-NEOs (detection rates: 98%) with the median values at 4.54 and 7.

Threshold reduction of GHz-repetition-rate passive mode-locking by tapering the gain fiber.

Passively mode-locked fiber lasers with GHz repetition rates have recently attracted significant attention in frontier research areas, including frequency-comb spectroscopy, coherent optical communication, photonic radar, micromachining, etc. In general, the threshold of passive mode-locking increases with the fundamental repetition rate, which is inversely proportional to the cavity length, and this sets a limit on the scalability of the fundamental repetition rate. To overcome this issue, here we propose to reduce the threshold of continuous-wave mode-locking (CWML) by precisely tapering the gain fiber, which can enhance the power density incident on the semiconductor saturable absorber mirror.

>10 GHz femtosecond fiber laser system at 2.0 μm.

We demonstrate a high-power 2.0-μm fiber laser system delivering femtosecond pulses with a fundamental repetition rate of >10 GHz, the highest value so far, to the best of our knowledge. The seed is a self-started fundamentally mode-locked Tm-doped fiber laser that has excellent power and spectral stabilities.

Vector soliton dynamics in a high-repetition-rate fiber laser.

The existence of vector solitons that arise from the birefringence nature of optical fibers has been increasingly of interest for the stability of mode-locked fiber lasers, particularly for those operating in the high-fundamental-repetition-rate regime, where a large amount of fiber birefringence is required to restore the phase relation between the orthogonally polarized vector solitons, resulting in stable mode-locking free of polarization rotation. These vector solitons can exhibit diverse time-varying polarization dynamics, which prevent industrial and scientific applications requiring stable and uniform pulse trains at high fundamental repetition rates. This pressing issue, however, has so far been rarely studied.

Biocompatible diameter-oscillating fiber with microlens endface.

Optical fibers have been widely applied to life science, such as laser delivering, fluorescence collection, biosensing, bioimaging, etc. To resolve the challenges of advanced multiphoton biophotonic applications utilizing ultrashort laser pulses, here we report a flexible diameter-oscillating fiber (DOF) with microlens endface fabricated by using Polydimethylsiloxane (PDMS) elastomers. The diameter of the DOF is designed to longitudinally vary for providing accurate dispersion management, which is important for near-infrared multiphoton biophotonics that usually involves ultrashort laser pulses.

Real-time multispeckle spectral-temporal measurement unveils the complexity of spatiotemporal solitons.

The dynamics of three-dimensional (3D) dissipative solitons originated from spatiotemporal interactions share many common characteristics with other multi-dimensional phenomena. Unveiling the dynamics of 3D solitons thus permits new routes for tackling multidisciplinary nonlinear problems and exploiting their instabilities. However, this remains an open challenge, as they are multi-dimensional, stochastic and non-repeatable.

High-power 2 GHz fs pulsed all-fiber amplified laser system at 2.0 µm.

High-power femtosecond (fs)-pulsed all-fiber lasers operating at high repetition rates are highly demanded for various applications, including laser micromachining, nonlinear optical imaging, high-speed optical sampling, arbitrary waveform generation, and frequency metrology. However, their performance has long been limited by either the average power, repetition rate, pulse width, or compactness, which prevent practical applications. In this work, we report a high repetition rate fs-pulsed all-fiber laser at 2.

>100 W GHz femtosecond burst mode all-fiber laser system at 1.0 µm.

In this work, we report a >100 W femtosecond (fs) burst mode all-fiber laser system at 1.0 µm that operates at an intra-burst repetition rate of up to 1.2 GHz.

Urinary Metabolites of Neonicotinoid Insecticides: Levels and Recommendations for Future Biomonitoring Studies in China.

Neonicotinoids (NEOs) are insecticides that are widely used around the world. Following exposure, NEOs get metabolized in human bodies. The biomarkers to assess human NEO exposure are not well described because of the lack of information on the metabolites of NEOs (m-NEOs).

Occurrence and transfer of benzophenone-type ultraviolet filters from the pregnant women to fetuses.

Benzophenone (BP)-type ultraviolet (UV) filters are widely used in personal care products. Some of them have been identified as endocrine disrupting chemicals. However, little is known about the occurrence of BP-type UV filters in paired maternal-fetal samples.

Novel and legacy poly- and perfluoroalkyl substances (PFASs) in indoor dust from urban, industrial, and e-waste dismantling areas: The emergence of PFAS alternatives in China.

With the phase out of perfluorooctanesulfonate (PFOS) and perfluorooctanoic acid (PFOA), the composition profiles of poly- and perfluoroalkyl substance (PFAS) in our living environment are unclear. In this study, 25 PFASs were analyzed in indoor dust samples collected from urban, industrial, and e-waste dismantling areas in China. PFOS alternatives, including 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA) (median: 5.

High-repetition-rate ultrafast fiber lasers.

Multi-gigahertz fundamental repetition rate, tunable repetition rate and wavelength, ultrafast fiber lasers at wavelengths of 1.0, 1.5, and 2.