Photonics

Research

10 pages, 2173 KiB

Open AccessArticle

Improved Carrier-Envelope Phase Determination Method for Few-Cycle Laser Pulses Using High-Order Above-Threshold Ionization

by Yu Zhou, Wei Quan, Meng Zhao, Zhiqiang Wang, Minghui Wang, Sijin Cheng, Jing Chen and Xiaojun Liu

Photonics 2022, 9(8), 528; https://doi.org/10.3390/photonics9080528 - 29 Jul 2022

Viewed by 1770

Abstract

Recent studies indicate that the stereo-ATI carrier-envelope phase meter (CEPM) is an effective method to determine the carrier-envelope phase (CEP) of each and every single few-cycle laser pulse. In this method, a two-dimensional parametric asymmetry plot (PAP), which can be obtained with the [...] Read more.

Recent studies indicate that the stereo-ATI carrier-envelope phase meter (CEPM) is an effective method to determine the carrier-envelope phase (CEP) of each and every single few-cycle laser pulse. In this method, a two-dimensional parametric asymmetry plot (PAP), which can be obtained with the measured data in two short time-of-flight intervals, is applied to extract the CEP. Thus, part of the data containing useful CEP information is discarded in the PAP method. In this work, an improved method was developed to effectively exploit most of the experimental data. By this method, we achieve a CEP precision of 57 mrad over the entire 2

π

range for 5.0 fs laser pulses. Full article

(This article belongs to the Special Issue Novel Nonlinear Phenomena with Strong Laser Fields)

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12 pages, 5592 KiB

Open AccessCommunication

Photoionization of Electrons in Degenerate Energy Level of Hydrogen Atom Induced by Strong Laser Pulses

by Peipei Xin, Tianhui Qiu, Hongyang Ma, Hua Yuan and Hongping Liu

Photonics 2022, 9(4), 256; https://doi.org/10.3390/photonics9040256 - 11 Apr 2022

Viewed by 2364

Abstract

Photoionization dynamics of bounded electrons in the ground state, the first and second excited states of a hydrogen atom, triggered by ultrashort near-infrared laser pulses, have been investigated in a transition regime (

γ \sim 1

) that offers both multiphoton and tunneling [...] Read more.

Photoionization dynamics of bounded electrons in the ground state, the first and second excited states of a hydrogen atom, triggered by ultrashort near-infrared laser pulses, have been investigated in a transition regime (

γ \sim 1

) that offers both multiphoton and tunneling features. Significant differences in spectral characteristics are found between the three low-energy states. The H(

2 s

) ionization probability is larger than the H(

2 p

) value with a special oscillating structure, but both are much greater than the ground state H(

1 s

) in a wide range of laser intensities. By comparing the momentum spectrum and angular distributions of low-energy photoelectrons released from these degenerate states, we find the H(

2 p

) state shows a stronger long-range Coulomb attraction force than the H(

2 s

) state on account of the difference in the initial electron wave packet. Furthermore, analysis of the photoelectron momentum distributions sheds light on both the first and second excited states with a symmetrical intercycle interference structure in a multicycle field but an intracycle interference of an asymmetric left-handed or right-handed rotating spectrum in a few-cycle field. By analyzing photoelectron spectroscopy, we identify the parity characteristics of photoelectrons in different energy intervals and their corresponding above-threshold single-photon ionization (ATSI) or above-threshold double-photon ionization (ATDI) processes. We finally present the momentum distributions of the electrons ionized by laser pulses with different profiles and find the carrier-envelope phase (CEP) is a strong factor in deciding the rotating structure of the emission spectrum, which provides a new method to distinguish the CEP of few-cycle pulses. Full article

(This article belongs to the Special Issue Novel Nonlinear Phenomena with Strong Laser Fields)

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10 pages, 1995 KiB

Open AccessCommunication

Observation of Neutron-Induced Absorption and Phase-Mismatch for Quasi-Phase-Matched Second Harmonic Generation in Congruent Lithium Niobate

by An-Chung Chiang, Jiunn-Hsing Chao, Shou-Tai Lin and Yuan-Yao Lin

Photonics 2022, 9(4), 225; https://doi.org/10.3390/photonics9040225 - 29 Mar 2022

Cited by 2 | Viewed by 1885

Abstract

We report an experimental observation of radiation-induced optical absorption in undoped congruent lithium niobate (LiNbO₃) crystals between the 190 nm and 3200 nm wavelength range. It was found that high-dose (up to 288 Gy) gamma rays did not significantly affect the [...] Read more.

We report an experimental observation of radiation-induced optical absorption in undoped congruent lithium niobate (LiNbO₃) crystals between the 190 nm and 3200 nm wavelength range. It was found that high-dose (up to 288 Gy) gamma rays did not significantly affect the optical absorption of LiNbO₃ during that wavelength range. However, upon the order of 10¹⁶ cm⁻² neutron irradiation, the change in the absorption coefficient was up to 0.6 cm⁻¹ at a wavelength of 532 nm and remained after 13 days in the dark at room temperature. The nonlinear optical performance was characterized by conducting third-order quasi-phase-matched second harmonic generation in neutron-irradiated periodically-poled LiNbO₃, showing that the phase-matching condition was altered, and the conversion efficiency was still comparable with a non-irradiated one. Full article

(This article belongs to the Special Issue Novel Nonlinear Phenomena with Strong Laser Fields)

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11 pages, 1811 KiB

Open AccessCommunication

Pre-Chirp-Managed Adiabatic Soliton Compression in Pressure-Gradient Hollow-Core Fibers

by Runzhi Chen, Zhuo Shi and Guoqing Chang

Photonics 2021, 8(9), 357; https://doi.org/10.3390/photonics8090357 - 27 Aug 2021

Cited by 3 | Viewed by 2344

Abstract

Post-pulse-compression is demanded to produce energetic few-cycle pulses. We propose pre-chirp-managed adiabatic soliton compression (ASC) in gas-filled pressure-gradient hollow-core fibers to suppress the detrimental pedestals and therefore significantly improve the compressed pulse quality. We show that two-stage ASC can compress 125 μJ, 130 [...] Read more.

Post-pulse-compression is demanded to produce energetic few-cycle pulses. We propose pre-chirp-managed adiabatic soliton compression (ASC) in gas-filled pressure-gradient hollow-core fibers to suppress the detrimental pedestals and therefore significantly improve the compressed pulse quality. We show that two-stage ASC can compress 125 μJ, 130 fs pulses at 2 μm to a nearly two-cycle pulse 15 fs in duration. Our analytical analysis suggests that ASC is in favor of compressing pulses centered at a longer wavelength. As an example, a 280 μJ, 220 fs Gaussian pulse at 4 μm is compressed to 60 fs with minimal pedestals. We expect that the resulting high-quality, energetic few-cycle pulses will find important applications in high-field science. Full article

(This article belongs to the Special Issue Novel Nonlinear Phenomena with Strong Laser Fields)

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10 pages, 3277 KiB

Open AccessCommunication

Surface Plasmon Resonance Dependent Third-Order Optical Nonlinearities of Silver Nanoplates

by Marcello Condorelli, Vittorio Scardaci, Mario Pulvirenti, Luisa D’Urso, Fortunato Neri, Giuseppe Compagnini and Enza Fazio

Photonics 2021, 8(8), 299; https://doi.org/10.3390/photonics8080299 - 27 Jul 2021

Cited by 10 | Viewed by 2202

Abstract

A systematic study of the surface plasmon resonance (SPR)-dependent nonlinear optical response of Ag nanoplates is presented and discussed. The Ag nanoplates were synthesized using the well-known seed-mediated growth method. By performing the z-scan method with a nanosecond laser (532 nm, 5 ns), [...] Read more.

A systematic study of the surface plasmon resonance (SPR)-dependent nonlinear optical response of Ag nanoplates is presented and discussed. The Ag nanoplates were synthesized using the well-known seed-mediated growth method. By performing the z-scan method with a nanosecond laser (532 nm, 5 ns), the optical nonlinearities of the Ag nanoplates, prepared tuning the SPR contribution in the 400–1000 nm range, were determined. The results showed a SPR-related competition between the saturable absorption and reverse saturable absorption mechanisms, while the nonlinear refraction changed from self-defocusing to self-focusing. Furthermore, the scattering effects contribute to determine the nature of the optical limiting response. The observed SPR-tunable third order optical nonlinearities make Ag nanoplates a suitable candidate to be used in different fields, i.e., laser pulse generation, optical limiting, or bio-imaging applications. Full article

(This article belongs to the Special Issue Novel Nonlinear Phenomena with Strong Laser Fields)

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14 pages, 1634 KiB

Open AccessCommunication

Monochromatic Conical IR Emission from Decaying KrF Laser Filaments in Xenon as Coherent Stimulated Four-Wave Mixing Process

by Igor V. Smetanin, Alexey V. Shutov, Nikolay N. Ustinovskii, Vladimir D. Zvorykin, Anna V. Bogatskaya and Alexander M. Popov

Photonics 2021, 8(2), 47; https://doi.org/10.3390/photonics8020047 - 12 Feb 2021

Viewed by 2451

Abstract

We develop theoretical background for the new nonlinear optical phenomenon of narrowly directed monochromatic IR conical emission which has been recently observed when 248-nm UV filaments propagate in xenon (V. D. Zvorykin, et al., Laser Phys. Lett. 13, 125404 (2016)). We treat it [...] Read more.

We develop theoretical background for the new nonlinear optical phenomenon of narrowly directed monochromatic IR conical emission which has been recently observed when 248-nm UV filaments propagate in xenon (V. D. Zvorykin, et al., Laser Phys. Lett. 13, 125404 (2016)). We treat it as coherent stimulated four-wave mixing process in which two pump KrF laser photons are converted into the coupled pair of resonance IR(828 nm) and VUV (147 nm) photons through

5 p^{5} (^{2} P_{3 / 2}) 6 p {[1 / 2]}_{0} \to 5 p^{5} (^{2} P_{3 / 2}) 6 s {[3 / 2]}_{1}^{o}

and

5 p^{5} (^{2} P_{3 / 2}) 6 s {[3 / 2]}_{1}^{o} \to

^{1} S_{0}

transitions. We explore the coherent interaction regime which proceeds at a time scale shorter than transverse relaxation time

T_{2}

. The momentum and energy conservation laws determine the characteristic angle of conical emission. We find that the threshold of this coherent process is determined by the KrF laser pump pulse area. Full article

(This article belongs to the Special Issue Novel Nonlinear Phenomena with Strong Laser Fields)

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12 pages, 1036 KiB

Open AccessCommunication

High-Order Harmonics Generation in Atomic and Molecular Zinc Plasmas

by Rashid A. Ganeev and Hiroto Kuroda

Photonics 2021, 8(2), 29; https://doi.org/10.3390/photonics8020029 - 25 Jan 2021

Cited by 11 | Viewed by 2396

Abstract

We demonstrate the variations of single harmonic resonance enhancement during high-order harmonics generation in zinc-containing atomic and molecular species at the conditions of single-color and two-color pumps of laser-induced plasmas by applying different laser sources. We show how selenides of this metal notably [...] Read more.

We demonstrate the variations of single harmonic resonance enhancement during high-order harmonics generation in zinc-containing atomic and molecular species at the conditions of single-color and two-color pumps of laser-induced plasmas by applying different laser sources. We show how selenides of this metal notably modify the enhancement of single (9th, 15th or 16th) harmonic compared with purely atomic zinc plasmas. The variations of single harmonic enhancement are demonstrated using fixed (806 nm) and tunable (1280–1440 nm) radiation. Full article

(This article belongs to the Special Issue Novel Nonlinear Phenomena with Strong Laser Fields)

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Graphical abstract

8 pages, 2280 KiB

Open AccessArticle

Understanding the Seeding Pulse-Induced Optical Amplification in

N_{2}^{+}

Pumped by 800 NM Femtosecond Laser Pulses

by Zhengquan Fan, Xiang Zhang, Qi Lu, Yu Luo, Qingqing Liang, Luqi Yuan, Zhedong Zhang and Yi Liu

Photonics 2020, 7(4), 99; https://doi.org/10.3390/photonics7040099 - 30 Oct 2020

Cited by 2 | Viewed by 3071

Abstract

Nitrogen ions pumped by intense femtosecond laser pulses present an optical gain at 391.4 nm, evident by energy amplification of an injected resonant seeding pulse. We report a time-resolved measurement of the amplification process with seeding pulses having varying intensities. It is found [...] Read more.

Nitrogen ions pumped by intense femtosecond laser pulses present an optical gain at 391.4 nm, evident by energy amplification of an injected resonant seeding pulse. We report a time-resolved measurement of the amplification process with seeding pulses having varying intensities. It is found that the amplification factor depends on the intensity of the seeding pulse and the effective temporal window for the optical gain becomes longer by applying more intense seeding pulses. These two features are in sharp contrast with classic pump-probe experiments, pinpointing the crucial role of macroscopic coherence and its dynamics during the lasing process. We further measure the temporal profile of the amplified emission for seeding pulse injected at different time delays. A complicated temporal behavior is observed, which highlights the nature of the superfluorescence. Full article

(This article belongs to the Special Issue Novel Nonlinear Phenomena with Strong Laser Fields)

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