It is known that a structure comprising a tens of microns thick, and ∼1 × 1 cm in size, layer of LiNbO attached to a Si prism can serve as an efficient Cherenkov-type converter of tens of microjoules-energy femtosecond laser pulses to broadband terahertz radiation. Here we experimentally demonstrate scaling up the terahertz energy and field strength by extending the width of the converter to several centimeters, expanding appropriately the pump laser beam, and increasing the pump pulse energy to hundreds of microjoules. In particular, chirped Ti:sapphire laser pulses of 450 fs duration and 600 µJ energy were converted to 1.2 µJ terahertz pulses, and 0.5 MV/cm peak terahertz field was obtained when pumping by unchirped laser pulses of 60 fs duration and 200 µJ energy.
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http://dx.doi.org/10.1364/OL.493358 | DOI Listing |
J Hand Surg Am
January 2025
Hand and Upper Extremity Division of Plastic and Reconstructive Surgery, University of California Davis, Sacramento, CA.
Purpose: Current technologies to define the zone of acute peripheral nerve injury intraoperatively are limited by surgical experience, time, cumbersome electrodiagnostic equipment, and interpreter reliability. In this pilot study, we evaluated a real-time, label-free optical technique for intraoperative nerve injury imaging. We hypothesize that fluorescence lifetime imaging (FLIm) will detect a difference between the time-resolved fluorescence signatures for acute crush injuries versus uninjured segments of peripheral nerves in sheep.
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January 2025
Department of Physics, University of Ottawa, Ottawa, ON, K1N 6N5, Canada.
We report a nonlinear terahertz (THz) detection device based on a metallic bull's-eye plasmonic antenna. The antenna, fabricated with femtosecond laser direct writing and deposited on a nonlinear gallium phosphide (GaP) crystal, focuses incoming THz waveforms within the sub-wavelength bull's eye region to locally enhance the THz field. Additionally, the plasmonic structure minimizes diffraction effects allowing a relatively long interaction length between the transmitted THz field and the co-propagating near-infrared gating pulse used in an electro-optic sampling configuration.
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January 2025
Laser Research Center, Vilnius University, Saulėtekio Avenue 10, LT-10223, Vilnius, Lithuania.
We present a comparative experimental study of supercontinuum generation in undoped scintillator crystals: bismuth germanate (BGO), yttrium orthosilicate (YSO), lutetium oxyorthosilicate (LSO), lutetium yttrium oxyorthosilicate (LYSO) and gadolinium gallium garnet (GGG), pumped by 180 fs fundamental harmonic pulses of an amplified Yb:KGW laser. In addition to these materials, experiments in yttrium aluminium garnet (YAG), potassium gadolinium tungstate (KGW) and lithium tantalate (LT) were performed under identical experimental settings (focusing geometry and sample thickness), which served for straightforward comparison of supercontinuum generation performances. The threshold and optimal (that produces optimized red-shifted spectral extent) pump pulse energies for supercontinuum generation were evaluated from detailed measurements of spectral broadening dynamics.
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December 2024
Institute of Atomic and Molecular Physics, Jilin University, Changchun, 130012, China. Electronic address:
Laser-induced breakdown spectroscopy (LIBS) is a rapidly evolving in-situ multi-element analysis technique that has significantly advanced the field of liquid analysis. This study employs a femtosecond laser for quantitative analysis of heavy metals in flowing liquids, exploring its detection sensitivity and accuracy. Femtosecond pulsed laser excitation of water in a dynamic environment generates plasma while effectively preventing liquid splashing.
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January 2025
Jilin Key Laboratory of Solid-State Laser Technology and Application, School of Science, Changchun, 130022, Jilin, China.
The response mechanism of a Four-Quadrant Photodetector (QPD) in an experimental setting was studied by irradiating a single QPD cell with a millisecond-pulsed laser. The response signal of the irradiated QPD cell varied with energy flux, pulse width, and applied bias, and comprised four main stages: an initial stage, decreasing barrier stage, holding stage, and recovery stage. Not only was the response signal of the irradiated cell affected by laser irradiation, but also the responses of the other three cells.
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