In this Letter, we report a flexible, plane-by-plane direct write inscription method for the development of tailored, tilted fiber Bragg gratings using a femtosecond laser. Compared to ultraviolet or femtosecond laser inscription based on the phase mask, interferometric, or point-by-point methods, the presented approach is far more flexible and offers several advantages. Laser inscription is made through the fiber coating, while the grating planes are controlled to minimize birefringence, with precise control over the wavelength location and strength of cladding modes. Tenth-order gratings were produced in the C+L bands so that higher-order gratings could be studied at shorter wavelengths. In particular, we show that the refractometric sensitivity depends on the grating order, ranging from ∼28 nm/refractive index unit (RIU) at ∼1510 nm to ∼13 nm/RIU at ∼1260 nm.
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http://dx.doi.org/10.1364/OL.42.005198 | DOI Listing |
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January 2025
Faculty of Physics and Astronomy, Adam Mickiewicz University, Poznan, 61-614, Poland.
The behavior of triple-cation mixed halide perovskite solar cells (PSCs) under ultrashort laser pulse irradiation at varying fluences is investigated, with a focus on local heating effects observed in femtosecond transient absorption (TA) studies. The carrier cooling time constant is found to increase from 230 fs at 2 µJ cm⁻ to 1.3 ps at 2 mJ cm⁻ while the charge population decay accelerates from tens of nanoseconds to the picosecond range within the same fluence range.
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January 2025
Center for Free-Electron Laser Science CFEL, Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany.
Sub-ångström spatial resolution of electron density coupled with sub-femtosecond to few-femtosecond temporal resolution is required to directly observe the dynamics of the electronic structure of a molecule after photoinitiation or some other ultrafast perturbation, such as by soft X-rays. Meeting this challenge, pushing the field of quantum crystallography to attosecond timescales, would bring insights into how the electronic and nuclear degrees of freedom couple, enable the study of quantum coherences involved in molecular dynamics, and ultimately enable these dynamics to be controlled. Here, we propose to reach this realm by employing convergent-beam x-ray crystallography with high-power attosecond pulses from a hard-x-ray free-electron laser.
View Article and Find Full Text PDFWe report lasing action in a femtosecond-laser-inscribed waveguide in thulium-doped barium-gallium-germanium oxide (BGG) glass. A laser cavity was assembled with this waveguide that provided a single-mode output of 62 mW when pumped at 1.6 µm.
View Article and Find Full Text PDFIn this Letter, we report an ultraflat high-power supercontinuum (SC) based on a low-loss short-length fluorotellurite fiber. A novel high-peak power dual-Raman soliton femtosecond laser is used as a pump source, which effectively extends the mid-infrared SC spectral range and enhances the flatness of the SC. Finally, we obtained a 10.
View Article and Find Full Text PDFThe emission of N lasing at 391 nm from 800 nm femtosecond laser filament in air at 1 atm presents significant challenges due to the quenching effect induced by oxygen molecules. We introduce a simple technique for the 391 nm N lasing emission induced by a corona electric field-assisted femtosecond filament in air. This technique greatly addresses the challenge of exciting a 391 nm lasing from 800 nm femtosecond laser filament in air at 1 atm.
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