1,720,963 research outputs found
Reconstruction algorithm for tunneling ionization with a perturbation for the time-domain observation of an electric-field
No full textAbstract We present a reconstruction algorithm developed for the temporal characterization method called tunneling ionization with a perturbation for the time-domain observation of an electric field (TIPTOE). The reconstruction algorithm considers the high-order contribution of an additional laser pulse to ionization, enabling the use of an intense additional laser pulse. Therefore, the signal-to-noise ratio of the TIPTOE measurement is improved by at least one order of magnitude compared to the first-order approximation. In addition, the high-order contribution provides additional information regarding the pulse envelope. The reconstruction algorithm was tested with ionization yields obtained by solving the time-dependent Schrödinger equation. The optimal conditions for accurate reconstruction were analyzed. The reconstruction algorithm was also tested using experimental data obtained using few-cycle laser pulses. The reconstructed pulses obtained under different dispersion conditions exhibited good consistency. These results confirm the validity and accuracy of the reconstruction process
Reconstruction of Femtosecond Laser Pulses from FROG Traces by Convolutional Neural Networks
No full textWe report on the reconstruction of ultrashort laser pulses from computer-simulated and experimental second harmonic generation-frequency resolved optical gating (SHG-FROG) spectrograms. In order to retrieve the spectral amplitude and phase we use a convolutional neural network trained on simulated SHG-FROG spectrograms and the corresponding spectral-domain fields employed as labels for the network, which is a complex field encompassing the full information about the amplitude and phase. Our results show excellent retrieval capabilities of the neural network in case of the simulated pulses. Although trained only on computer generated data, the method shows promising results regarding experimentally measured pulses. © 2023 by the authors.11Nsciescopu
Tailoring octave-spanning ultrashort laser pulses using multiple prisms
Get PDFWe demonstrate a novel pulse shaper in which an incident laser beam is angularly dispersed by a first prism, and then it is split into separate beams using multiple prisms. Since this new pulse shaper offers independent control of the amplitude and phase of the separate beams, it can produce pulses having desired temporal shapes. Furthermore, it imposes a significant amount of negative group delay dispersion (GDD) over an octave spectrum near visible, which can compensate for a positive GDD accumulated in the process of spectral broadening. Consequently, single-cycle or few-cycle laser pulses can be produced without the need for chirped mirrors.11Nsciescopu
Spectral response of chirp-dependent femtosecond laser filamentation in air
No full textFilamentation is a nonlinear optical phenomenon that involves the interplay between Kerr lens self-focusing and plasma defocusing, holding promise for practical applications in open-air environments over long distances. This process significantly alters the characteristics of laser pulses, making the control of laser properties a pivotal issue. In this study, we investigated the effects of laser energy and chirp on the spectral modulation of femtosecond laser pulses caused by filamentation in air. Negatively and positively chirped pulses exhibit distinct characteristics in the spectra measured after the filamentation. Negatively chirped pulses have broader spectral broadening and a stronger dependence on initial laser energy than positively chirped pulses, making them suitable for generating few-cycle pulses and applications requiring white light. In contrast, positively chirped pulses can be advantageous for applications requiring long-distance transmission of high-energy laser pulse. Our findings reveal the fundamental characteristics of femtosecond laser filamentation in air, thereby expanding the scope of possible atmospheric applications. © 2023, The Korean Physical Society.11Nsciescopuskc
2.3-cycle mid-infrared pulses from hybrid thin-plate post-compression at 7 W average power
Get PDF© 2020 The Authors. Published by Elsevier B.V. Output pulses of a 100 kHz mid-infrared OPCPA system are post-compressed from 4.7 cycles down to 2.3 cycles by using a combination of a dielectric and a semiconductor crystal in a hybrid thin plate setup. Efficient spectral broadening is demonstrated with 11 W average input power. After compression the output power reached 6.8 W with exceptional CEP and energy stability for a several hours. The post-compressed pulses were carefully characterized in both temporal and spatial domains, resulting in 2.3-cycle temporal duration at 3.1 μm central wavelength with a temporal Strehl ratio of 0.73 and a spatial Strehl ratio of 0.97. Thermal limitations due to multiphoton absorption of semiconductors present at this power level are explored by temperature measurements, which are supported by detailed numerical simulations. Upscaling for higher average powers was also investigated11sciescopu
Temporal characterization of femtosecond laser pulses using tunneling ionization in the UV, visible, and mid-IR ranges
Get PDF© 2019, The Author(s).To generalize the applicability of the temporal characterization technique called “tunneling ionization with a perturbation for the time-domain observation of an electric field” (TIPTOE), the technique is examined in the multicycle regime over a broad wavelength range, from the UV to the IR range. The technique is rigorously analyzed first by solving the time-dependent Schrödinger equation. Then, experimental verification is demonstrated over an almost 5-octave wavelength range at 266, 1800, 4000 and 8000 nm by utilizing the same nonlinear medium – air. The experimentally obtained dispersion values of the materials used for the dispersion control show very good agreement with the ones calculated using the material dispersion data and the pulse duration results obtained for 1800 and 4000 nm agree well with the frequency-resolved optical gating measurements. The universality of TIPTOE arises from its phase-matching-free nature and its unprecedented broadband operation range11sciescopu
Generation of a single-cycle pulse using a two-stage compressor and its temporal characterization using a tunnelling ionization method
Get PDFA single-cycle laser pulse was generated using a two-stage compressor and characterized using a pulse characterization technique based on tunnelling ionization. A 25-fs, 800-nm laser pulse was compressed to 5.5 fs using a gas-filled hollow-core fibre and a set of chirped mirrors. The laser pulse was further compressed, down to the single-cycle limit by propagation through multiple fused-silica plates and another set of chirped mirrors. The two-stage compressor mitigates the development of higher-order dispersion during spectral broadening. Thus, a single-cycle pulse was generated by compensating the second-order dispersion using chirped mirrors. The duration of the single-cycle pulse was 2.5 fs, while its transform-limited duration was 2.2 fs. A continuum extreme ultraviolet spectrum was obtained through high-harmonic generation without applying any temporal gating technique. The continuum spectrum was shown to have a strong dependence on the carrier-envelope phase of the laser pulse, confirming the generation of a single-cycle pulse. © 2019, The Author(s
Direct sampling of a light wave in air
No full textTemporal characterization of a laser pulse is an essential task in many applications. Temporal characterization methods that are currently available support only a limited spectral bandwidth without information on the carrier-envelope phase (CEP) of the laser pulse or require complicated equipment in a vacuum environment. Here we demonstrate that an arbitrary time-dependent laser field can be directly sampled using subcycle tunneling ionization in a gaseous medium or in air. The subcycle ionization is used as a fast temporal gate for the direct sampling of the laser field. This unique approach enables the complete temporal characterization of the laser field, including its CEP, for a broad spectral range in ambient air, providing a universal tool for the precise measurement of the laser field. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreemen1
Ionization yield measurement using metal electrodes with a static electric field in ambient air
No full text© 2020 IOP Publishing Ltd. The amount of ionization produced in a laser-matter interaction provides critical information in studying strong field physics and attosecond science. The amount of ionization can be accurately measured in vacuum using a photoelectron/ion spectrometer by counting the number of charged particles. However, an ionization yield measurement in ambient air requires the considerations of post processes such as drift and recombination of charged particles, which may add an unwanted nonlinearity to the measurement. Here we investigate the kinetics of the charged particles after optical field ionization in ambient air under a static bias field. A simple kinetic model is used in which coupled rate equations are numerically solved. The kinetic model explains the recombination loss of the charged particles observed in ionization yield measurements. A condition for the static bias field is derived for an accurate ionization yield measurement11sciescopu
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