Applied Sciences

Research

10 pages, 1131 KiB

Open AccessFeature PaperArticle

Generation and Characterization of Mid-Infrared Supercontinuum in Bulk YAG Pumped by Femtosecond 1937 nm Pulses from a Regenerative Amplifier

by Seyed Ali Rezvani, Yutaka Nomura and Takao Fuji

Appl. Sci. 2019, 9(16), 3399; https://doi.org/10.3390/app9163399 - 18 Aug 2019

Cited by 3 | Viewed by 3526

Abstract

We have demonstrated the generation of supercontinuum (SC) pulses in bulk, using femtosecond pulses directly derived from a Tm:YAP regenerative amplifier. The SC spans from 380 nm–4

μ

m. Such an SC combined with the applied 1937-nm pump pulse can be used in [...] Read more.

We have demonstrated the generation of supercontinuum (SC) pulses in bulk, using femtosecond pulses directly derived from a Tm:YAP regenerative amplifier. The SC spans from 380 nm–4

μ

m. Such an SC combined with the applied 1937-nm pump pulse can be used in a mid-infrared optical parametric amplifier (MIR-OPA). A full characterization of the phase and stability of the SC provides important insight into the performance of such MIR-OPA systems. Using cross-correlation frequency-resolved optical gating (XFROG), we characterized the properties of the MIR section of the SC that can be used as a seed pulse in an MIR-OPA system. The pulse-to-pulse instability rooted in the intrinsic properties of the self-phase modulation process was observed in the retrieved trace and spectrum of the SC. In addition, the effect of the pump pulse quality was studied on the obtainable SC pulses. Full article

(This article belongs to the Special Issue Ultrafast Laser Pulses)

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9 pages, 1847 KiB

Open AccessArticle

Generation of Ultrafast Optical Pulses via Molecular Modulation in Ambient Air

by Yuta Nakano, Anton D. Shutov, Totaro Imasaka and Alexei V. Sokolov

Appl. Sci. 2019, 9(12), 2509; https://doi.org/10.3390/app9122509 - 20 Jun 2019

Cited by 1 | Viewed by 2598

Abstract

We investigated the possibility of making ever-shorter optical pulses by using the nonlinearity of ambient air. We produced a broad spectrum consisting of mutually coherent optical sidebands via collinear Raman generation driven by two picosecond laser pulses that are Raman-resonant with molecular vibrations [...] Read more.

We investigated the possibility of making ever-shorter optical pulses by using the nonlinearity of ambient air. We produced a broad spectrum consisting of mutually coherent optical sidebands via collinear Raman generation driven by two picosecond laser pulses that are Raman-resonant with molecular vibrations of nitrogen. We demonstrated the ability to adjust the sideband phases via dispersion control which we accomplished by changing the optical path length of the generated multi-color beam through a pair of tilted glass plates. The resultant measured phases suggest the generation of a 3-fs optical pulse train. Full article

(This article belongs to the Special Issue Ultrafast Laser Pulses)

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11 pages, 1881 KiB

Open AccessArticle

A High Resolution XUV Grating Monochromator for the Spectral Selection of Ultrashort Harmonic Pulses

by Nicola Fabris, Paolo Miotti, Fabio Frassetto and Luca Poletto

Appl. Sci. 2019, 9(12), 2502; https://doi.org/10.3390/app9122502 - 19 Jun 2019

Cited by 7 | Viewed by 3703

Abstract

A new monochromator with high spectral resolution in the extreme ultraviolet (XUV) has been developed for high-order laser harmonics selection. The system has three optical elements—a cylindrical (or spherical) focusing mirror, a uniform-line-spaced plane grating, and a plane mirror. The last element is [...] Read more.

A new monochromator with high spectral resolution in the extreme ultraviolet (XUV) has been developed for high-order laser harmonics selection. The system has three optical elements—a cylindrical (or spherical) focusing mirror, a uniform-line-spaced plane grating, and a plane mirror. The last element is required to maintain the focus on a fixed vertical slit when the grating subtended angle is changed in order to minimize the spectral defocusing aberration. The parameters of the focusing mirror are determined to introduce a coma that compensates for the coma given by the grating. The possibility of using two interchangeable gratings made the set-up optimized for a broad energy range of 12–50 eV. As a design test case, the set-up has been applied to a selection of the discrete spectral lines emitted by a gas-discharge lamp as the XUV source, obtaining a resolving power E/

Δ

E > 3000. Full article

(This article belongs to the Special Issue Ultrafast Laser Pulses)

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21 pages, 5473 KiB

Open AccessArticle

Femtosecond Beam Transformation Effects in Water, Enabling Increased Throughput Micromachining in Transparent Materials

by Simas Butkus, Eugenijus Gaižauskas, Lina Mačernytė, Vytautas Jukna, Domas Paipulas and Valdas Sirutkaitis

Appl. Sci. 2019, 9(12), 2405; https://doi.org/10.3390/app9122405 - 13 Jun 2019

Cited by 11 | Viewed by 3629

Abstract

Femtosecond lasers are widely applied in scientific and industrial fields. Recent trends in the laser market show decreasing prices for femtosecond units, which will ultimately lead to the opening of new markets that were inaccessible in the past due to the high costs [...] Read more.

Femtosecond lasers are widely applied in scientific and industrial fields. Recent trends in the laser market show decreasing prices for femtosecond units, which will ultimately lead to the opening of new markets that were inaccessible in the past due to the high costs of such systems. To this end, new techniques that enable micromachining of materials with increased efficiency are interesting. In this article, we demonstrate a technique that may be used for cutting and drilling various materials. By placing a layer of water on top of the samples and loosely focusing laser light on the surface, it was found that the micromachining throughput is increased by up to 10-fold as compared with micromachining without the water layer (conventional focusing in air), however, the main reasons for the increase in fabrication efficiency have not been fully understood until now. By modelling the propagation of the femtosecond pulses by means of the nonlinear modified Schrodinger equation through the water layer, we show that the increased throughput is attributed to the changing of the Gaussian intensity profile. In addition, we confirm these findings by numerically modelling the ablated crater formation. Full article

(This article belongs to the Special Issue Ultrafast Laser Pulses)

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14 pages, 1634 KiB

Open AccessArticle

Application of Quasi-Phase Matching Concept for Enhancement of High-Order Harmonics of Ultrashort Laser Pulses in Plasmas

by R. A. Ganeev, S. Y. Stremoukhov, A. V. Andreev and A. S. Alnaser

Appl. Sci. 2019, 9(8), 1701; https://doi.org/10.3390/app9081701 - 25 Apr 2019

Cited by 14 | Viewed by 3473

Abstract

Novel methods of coherent short-wavelength sources generation require thorough analysis for their further amendments and practical implementations. In this work, we report on the quasi-phase matching (QPM) of high-order harmonics generation during the propagation of single- and two-color femtosecond pulses through multi-jet plasmas, [...] Read more.

Novel methods of coherent short-wavelength sources generation require thorough analysis for their further amendments and practical implementations. In this work, we report on the quasi-phase matching (QPM) of high-order harmonics generation during the propagation of single- and two-color femtosecond pulses through multi-jet plasmas, which allows the enhancement of groups of harmonics in different ranges of extreme ultraviolet. The role of the number of coherent zones; sizes of plasma jets and the distance between them; plasma formation conditions, and the characteristics of the fundamental radiation on the harmonic efficiency at quasi-phase matching (QPM) conditions are analyzed. We demonstrate the ~40× enhancement factor of the maximally-enhanced harmonic with respect to the one generated at ordinary conditions in the imperforated plasma. Full article

(This article belongs to the Special Issue Ultrafast Laser Pulses)

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12 pages, 4520 KiB

Open AccessArticle

Charge-Line Dual-FET High-Repetition-Rate Pulsed Laser Driver

by Mateusz Żbik and Piotr Zbigniew Wieczorek

Appl. Sci. 2019, 9(7), 1289; https://doi.org/10.3390/app9071289 - 27 Mar 2019

Cited by 6 | Viewed by 6309

Abstract

Most modern pulsed laser systems require versatile laser diode drivers. A state-of-the-art pulsed laser driver should provide precise peak power regulation, high repetition rate, and pulse duration control. A new, charge line dual-FET transistor circuit structure was developed to provide all these features. [...] Read more.

Most modern pulsed laser systems require versatile laser diode drivers. A state-of-the-art pulsed laser driver should provide precise peak power regulation, high repetition rate, and pulse duration control. A new, charge line dual-FET transistor circuit structure was developed to provide all these features. The pulsed modulation current is adjustable up to I_max = 1.2 A, with the laser diode forward voltage acceptable up to U_{F max} = 20 V. The maximum repetition rate is limited by a charge line circuit to f_{rep max} = 20 MHz. Compared to the conventional single transistor drivers, the solution proposed in this paper allows a precise, high resolution width regulation to be obtained, whereas a low pulse jitter is ensured. In the solution, two separate, out-of-phase signals are used to trigger the individual Field Effect Transistors (FET). The resultant pulsed modulation current full-width-at-half-maxima (FWHM) is regulated from ~200 ps up to 2 ns. All control and timing signals are generated with a popular Field-Programmable Gate Array (FPGA) digital circuitry. The use of standard FPGA devices ensures the low cost and high reliability of the circuit, which are not available in laser drivers consisting of sophisticated analogue adjustable delay circuits. Full article

(This article belongs to the Special Issue Ultrafast Laser Pulses)

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8 pages, 1258 KiB

Open AccessArticle

Step-Pulse Modulation of Gain-Switched Semiconductor Pulsed Laser

by Bin Li, Changyan Sun, Yun Ling, Heng Zhou and Kun Qiu

Appl. Sci. 2019, 9(3), 602; https://doi.org/10.3390/app9030602 - 12 Feb 2019

Cited by 4 | Viewed by 5554

Abstract

To improve the peak power and extinction ratio and produce ultra-short pulses, a novel approach is presented in this paper offers a highly effective modulated method for a gain-switched semiconductor laser by using step-pulse signal modulation. For the purpose of single pulse output, [...] Read more.

To improve the peak power and extinction ratio and produce ultra-short pulses, a novel approach is presented in this paper offers a highly effective modulated method for a gain-switched semiconductor laser by using step-pulse signal modulation. For the purpose of single pulse output, then the effects on the output from the gain-switched semiconductor laser are studied by simulating single mode rate equation when changing the amplitude and width of the modulated signal. The results show that the proposed method can effectively accelerate the accumulation speed of the population inversion and we can acquire the output pulse with higher peak power and shorter width. Compared with the traditional rectangular wave modulation, this method is advantageous to obtain a high gain switching effect by increasing the second modulation current and reduce the pulse width to saturation at the best working point. It can be incorporated as a practical and cost-effective approach for many fields which need high extinction ratio short pulse, such as the optical time domain reflectometry. Full article

(This article belongs to the Special Issue Ultrafast Laser Pulses)

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30 pages, 7812 KiB

Open AccessArticle

Analytical Solutions for the Propagation of UltraShort and UltraSharp Pulses in Dispersive Media

by Er’el Granot

Appl. Sci. 2019, 9(3), 527; https://doi.org/10.3390/app9030527 - 4 Feb 2019

Cited by 6 | Viewed by 3160

Abstract

Ultrashort pulses are severely distorted even by low dispersive media. While the mathematical analysis of dispersion is well known, the technical literature focuses on pulses, Gaussian and Airy pulses, which keep their shape. However, the cases where the shape of the pulse is [...] Read more.

Ultrashort pulses are severely distorted even by low dispersive media. While the mathematical analysis of dispersion is well known, the technical literature focuses on pulses, Gaussian and Airy pulses, which keep their shape. However, the cases where the shape of the pulse is unaffected by dispersion is the exception rather than the norm. It is the objective of this paper to present a variety of pulse profiles, which have analytical expressions but can simulate real-physical pulses with great accuracy. In particular, the dynamics of smooth rectangular pulses, physical Nyquist-Sinc pulses, and slowly rising but sharply decaying ones (and vice versa) are presented. Besides the usage of this paper as a handbook of analytical expressions for pulse propagations in a dispersive medium, there are several new findings. The main findings are the analytical expressions for the propagation of chirped rectangular pulses, which converge to extremely short pulses; an analytical approximation for the propagation of super-Gaussian pulses; the propagation of the Nyquist-Sinc Pulse with smooth spectral boundaries; and an analytical expression for a physical realization of an attenuation compensating Airy pulse. Full article

(This article belongs to the Special Issue Ultrafast Laser Pulses)

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19 pages, 4531 KiB

Open AccessFeature PaperArticle

Spin-ARPES EUV Beamline for Ultrafast Materials Research and Development

by Zhonghui Nie, Ion Cristian Edmond Turcu, Yao Li, Xiaoqian Zhang, Liang He, Jian Tu, Zhiqiang Ni, Huangfeng Xu, Yequan Chen, Xuezhong Ruan, Fabio Frassetto, Paolo Miotti, Nicola Fabris, Luca Poletto, Jing Wu, Qiangsheng Lu, Chang Liu, Thorsten Kampen, Ya Zhai, Wenqing Liu, Cephise Cacho, Xuefeng Wang, Fengqiu Wang, Yi Shi, Rong Zhang and Yongbing Xu Show full author list Hide full author list

Appl. Sci. 2019, 9(3), 370; https://doi.org/10.3390/app9030370 - 22 Jan 2019

Cited by 15 | Viewed by 8374

Abstract

A new femtosecond, Extreme Ultraviolet (EUV), Time Resolved Spin-Angle Resolved Photo-Emission Spectroscopy (TR-Spin-ARPES) beamline was developed for ultrafast materials research and development. This 50-fs laser-driven, table-top beamline is an integral part of the “Ultrafast Spintronic Materials Facility”, dedicated to engineering ultrafast materials. This [...] Read more.

A new femtosecond, Extreme Ultraviolet (EUV), Time Resolved Spin-Angle Resolved Photo-Emission Spectroscopy (TR-Spin-ARPES) beamline was developed for ultrafast materials research and development. This 50-fs laser-driven, table-top beamline is an integral part of the “Ultrafast Spintronic Materials Facility”, dedicated to engineering ultrafast materials. This facility provides a fast and in-situ analysis and development of new materials. The EUV source based on high harmonic generation process emits 2.3 × 10¹¹ photons/second (2.3 × 10⁸ photons/pulse) at H23 (35.7 eV) and its photon energy ranges from 10 eV to 75 eV, which enables surface sensitive studies of the electronic structure dynamics. The EUV monochromator provides the narrow bandwidth of the EUV beamline while preserving its pulse duration in an energy range of 10–100 eV. Ultrafast surface photovoltaic effect with ~650 fs rise-time was observed in p-GaAs (100) from time-resolved ARPES spectra. The data acquisition time could be reduced by over two orders of magnitude by scaling the laser driver from 1 KHz, 4W to MHz, KW average power. Full article

(This article belongs to the Special Issue Ultrafast Laser Pulses)

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7 pages, 1432 KiB

Open AccessArticle

500-kHz Level High Energy Double-Pass Nd:YVO₄ Picosecond Amplifier with Optic–Optic Efficiency of 51%

by Xuesheng Liu, Huan He, Yiheng Song, Congcong Wang and Zhiyong Wang

Appl. Sci. 2019, 9(2), 219; https://doi.org/10.3390/app9020219 - 9 Jan 2019

Cited by 2 | Viewed by 3707

Abstract

We have demonstrated a high pulse energy and high optic–optic efficiency double-pass picosecond (ps) master oscillator power amplifier system of 1064 nm at a pulse repetition rate of 500 kHz. A 500 kHz, 7.68 μJ picosecond laser is used as the seed laser. [...] Read more.

We have demonstrated a high pulse energy and high optic–optic efficiency double-pass picosecond (ps) master oscillator power amplifier system of 1064 nm at a pulse repetition rate of 500 kHz. A 500 kHz, 7.68 μJ picosecond laser is used as the seed laser. Through one stage double-pass traveling-wave amplifier, a maximum output power of 16.19 W at a pump power of 31.7 W is generated with the optic–optic efficiency of 51.07%. The output pulse duration is 17.6 ps, corresponding to the pulse energy of 32.38 μJ. The beam quality factor

M^{2}

were measured to be 1.28 and 1.17 along the x, y axis direction, respectively. Full article

(This article belongs to the Special Issue Ultrafast Laser Pulses)

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9 pages, 2243 KiB

Open AccessArticle

Low Threshold Plasmonic Nanolaser Based on Graphene

by Litu Xu, Fang Li, Shuai Liu, Fuqiang Yao and Yahui Liu

Appl. Sci. 2018, 8(11), 2186; https://doi.org/10.3390/app8112186 - 8 Nov 2018

Cited by 20 | Viewed by 3121

Abstract

A hybrid plasmonic nanolaser based on nanowire/air slot/semicircular graphene and metal wire structure was designed. In this structure, the waveguides in the nanowires and the graphene-metal interface are coupled to form a hybrid plasma mode, which effectively reduces the metal loss. The mode [...] Read more.

A hybrid plasmonic nanolaser based on nanowire/air slot/semicircular graphene and metal wire structure was designed. In this structure, the waveguides in the nanowires and the graphene-metal interface are coupled to form a hybrid plasma mode, which effectively reduces the metal loss. The mode and strong coupling of the laser are analyzed by using the finite-element method. Its electric field distribution, propagation loss, normalized mode area, quality factor, and lasing threshold are studied with the different geometric model. Simulation results reveal that the performance of the laser using this structure can be optimized by adjusting the model parameters. Under the optimal parameters, the effective propagation loss is only 0.0096, and the lasing threshold can be as low as 0.14 μm⁻¹. This structure can achieve deep sub-wavelength confinement and low-loss transmission, and provides technical support for the miniaturization and integration of nano-devices. Full article

(This article belongs to the Special Issue Ultrafast Laser Pulses)

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9 pages, 1714 KiB

Open AccessArticle

Design of Surface Plasmon Nanolaser Based on MoS₂

by Litu Xu, Fang Li, Lai Wei, Jianxin Zhou and Shuai Liu

Appl. Sci. 2018, 8(11), 2110; https://doi.org/10.3390/app8112110 - 1 Nov 2018

Cited by 23 | Viewed by 3174

Abstract

The paper has proposed a new structure based on MoS₂. The electric field distribution, the locality and the loss of the mode, and the threshold under different geometric shapes and parameters are investigated using COMSOL Multiphysics software, based on the finite [...] Read more.

The paper has proposed a new structure based on MoS₂. The electric field distribution, the locality and the loss of the mode, and the threshold under different geometric shapes and parameters are investigated using COMSOL Multiphysics software, based on the finite element method. The different influenced degree of each component is also analyzed. Simulation results reveal that this kind of nanolaser has a low loss and high field confinement ability, the radius of CdS and Ag make a major contribution to the low loss and low threshold, and field confinement ability is mainly affected by the height of air gap. Under optimal parameters, effective propagation loss is only 0.00013, and the lasing threshold can be as low as 0.11 μm⁻¹. The results provide theory and technique support to the field of new nanolaser design. Full article

(This article belongs to the Special Issue Ultrafast Laser Pulses)

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8 pages, 2677 KiB

Open AccessArticle

Quality-Improved GaN Epitaxial Layers Grown on Striped Patterned Sapphire Substrates Ablated by Femtosecond Laser

by Yichao Xu, Jun Zou, Xiaoyan Lin, Wenjuan Wu, Wenbo Li, Bobo Yang and Mingming Shi

Appl. Sci. 2018, 8(10), 1842; https://doi.org/10.3390/app8101842 - 8 Oct 2018

Cited by 9 | Viewed by 3265

Abstract

In this work, we propose a new approach to create striped patterned sapphire substrate (PSS) under the circumstance that grooved patterned sapphire substrate technology exhibits more potential to reduce dislocation density in GaN (gallium nitride) epilayers. The striped grooves of patterned sapphire substrate [...] Read more.

In this work, we propose a new approach to create striped patterned sapphire substrate (PSS) under the circumstance that grooved patterned sapphire substrate technology exhibits more potential to reduce dislocation density in GaN (gallium nitride) epilayers. The striped grooves of patterned sapphire substrate are ablated by femtosecond laser. After the process of metal-organic chemical vapor deposition (MOCVD) method, the c-plane GaN epitaxial layers grown on striped PSS have larger crystallite size, which brings much less crystal boundary. There is much less compressive stress between the GaN crystals which improves the smoothness and compactness of GaN epilayers. This result demonstrates a significant improvement in the crystallinity of the c-plane GaN epitaxial layers grown on striped PSS. Full article

(This article belongs to the Special Issue Ultrafast Laser Pulses)

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12 pages, 848 KiB

Open AccessArticle

Ablation of Copper Metal Films by Femtosecond Laser Multipulse Irradiation

by Ahmed Abdelmalek, Zeyneb Bedrane, El-Hachemi Amara, Belén Sotillo, Vibhav Bharadwaj, Roberta Ramponi and Shane M. Eaton

Appl. Sci. 2018, 8(10), 1826; https://doi.org/10.3390/app8101826 - 5 Oct 2018

Cited by 25 | Viewed by 5589

Abstract

Ablation of copper using multipulse femtosecond laser irradiation with an 800 nm wavelength and 120-fs pulse duration is investigated theoretically. A two-temperature model, which includes dynamic optical and thermal-physical properties, is considered. The numerical results of the material thermal response obtained by varying [...] Read more.

Ablation of copper using multipulse femtosecond laser irradiation with an 800 nm wavelength and 120-fs pulse duration is investigated theoretically. A two-temperature model, which includes dynamic optical and thermal-physical properties, is considered. The numerical results of the material thermal response obtained by varying the pulse number, the separation times between pulses and laser fluences are presented. Our results show that the increasing of pulse number with a separation time less than the thermal relaxation time can dramatically enhance the lattice temperature without a noticeable increase in ablation depth. Therefore, we suggest that the vaporization rate can be augmented in comparison to the melting rate during the same single-phase explosion at the same total fluence where a fast heat accumulation effect plays an important role for cleaner ablation during micromachining. Full article

(This article belongs to the Special Issue Ultrafast Laser Pulses)

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14 pages, 720 KiB

Open AccessFeature PaperArticle

Multidimensional Analysis of Time-Resolved Charged Particle Imaging Experiments

by Vincent Loriot, Luis Bañares and Rebeca De Nalda

Appl. Sci. 2018, 8(8), 1227; https://doi.org/10.3390/app8081227 - 26 Jul 2018

Cited by 3 | Viewed by 3548

Abstract

We present a tutorial to realize a multidimensional fitting procedure capable of extracting all the relevant information contained in a sequence of charged particle images acquired as a function of time in femtosecond pump–probe experiments. The images are reproduced using a 3D fitting [...] Read more.

We present a tutorial to realize a multidimensional fitting procedure capable of extracting all the relevant information contained in a sequence of charged particle images acquired as a function of time in femtosecond pump–probe experiments. The images are reproduced using a 3D fitting method, which provides the velocity (or center-of-mass kinetic energy) and angular distributions contained in the images and their time evolution. A detailed example of the method is shown through the analysis of the time-resolved predissociation dynamics of CH

_{3}

I on the B-band origin (Gitzinger et al., J. Chem. Phys.2010, 133, 234313). We show that the multidimensional approach is essential for the analysis of complex images that contain several overlapping contributions where reduced dimensionality analyses cannot provide a reliable description of the features present in the image sequence. This methodology can be generalized to many types of multidimensional data analysis. Full article

(This article belongs to the Special Issue Ultrafast Laser Pulses)

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7 pages, 1812 KiB

Open AccessArticle

Stable Q-Switched Mode-Locking of 2.7 μm Er:Y₂O₃ Ceramic Laser Using a Semiconductor Saturable Absorber

by Hao Xue, Li Wang, Wei Zhou, Haotian Wang, Jun Wang, Dingyuan Tang and Deyuan Shen

Appl. Sci. 2018, 8(7), 1155; https://doi.org/10.3390/app8071155 - 17 Jul 2018

Cited by 6 | Viewed by 3302

Abstract

This paper studies synchronous Q-switch and mode-locking of an 2.7 μm Er:Y₂O₃ ceramic laser pumped with a high brightness 976 nm fiber laser and using a semiconductor saturable absorber mirror. The Er:Y₂O₃ ceramic is home-developed with Er [...] Read more.

This paper studies synchronous Q-switch and mode-locking of an 2.7 μm Er:Y₂O₃ ceramic laser pumped with a high brightness 976 nm fiber laser and using a semiconductor saturable absorber mirror. The Er:Y₂O₃ ceramic is home-developed with Er³⁺ doping concentration of 7 at.%. The laser generated ~92 mW of average output power with stable mode-locked pulses of 100% modulation depth and 130 MHz repetition rate embedded inside Q-switched envelopes of ~1.2 μs width. Repetition rates of the Q-switched pulse envelopes are tunable from 5.1 kHz to 29 kHz with the width varying from 2.7 μs to 1.2 μs. Full article

(This article belongs to the Special Issue Ultrafast Laser Pulses)

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Review

Jump to: Research, Other

22 pages, 5211 KiB

Open AccessReview

Modeling and Analysis of High-Power Ti:sapphire Laser Amplifiers–A Review

by Jihoon Jeong, Seryeyohan Cho, Seungjin Hwang, Bongju Lee and Tae Jun Yu

Appl. Sci. 2019, 9(12), 2396; https://doi.org/10.3390/app9122396 - 12 Jun 2019

Cited by 6 | Viewed by 4408

Abstract

We have introduced several factors that can be useful for the modeling and analysis of high-power Ti:sapphire laser amplifiers. The amplification model includes the phase distortion effect caused by the atomic phase shift (APS) in gain medium and the thermal-induced phase distortion effect [...] Read more.

We have introduced several factors that can be useful for the modeling and analysis of high-power Ti:sapphire laser amplifiers. The amplification model includes the phase distortion effect caused by the atomic phase shift (APS) in gain medium and the thermal-induced phase distortion effect caused by the high-average-power amplification. We have provided an accurate amplification model for the development of ultra-high-intensity and high-average-power lasers. Full article

(This article belongs to the Special Issue Ultrafast Laser Pulses)

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22 pages, 5742 KiB

Open AccessReview

Recent Advances in Femtosecond Laser-Induced Surface Structuring for Oil–Water Separation

by Ali Sami Alnaser, Sharjeel Ahmed Khan, Rashid Ashirovich Ganeev and Emmanuel Stratakis

Appl. Sci. 2019, 9(8), 1554; https://doi.org/10.3390/app9081554 - 15 Apr 2019

Cited by 47 | Viewed by 7453

Abstract

Femtosecond (FS) laser-induced surface structuring is a robust, maskless, non-contact, and single-step process for producing micro- and nanoscale structures on a material’s surface, which remarkably alters the optical, chemical, wetting, and tribological properties of that material. Wettability control, in particular, is of high [...] Read more.

Femtosecond (FS) laser-induced surface structuring is a robust, maskless, non-contact, and single-step process for producing micro- and nanoscale structures on a material’s surface, which remarkably alters the optical, chemical, wetting, and tribological properties of that material. Wettability control, in particular, is of high significance in various applications, including self-cleaning, anti-fouling, anti-icing, anti-corrosion, and, recently, oil–water separation. Due to growing energy demands and rapid industrialization, oil spill accidents and organic industrial discharges frequently take place. This poses an imminent threat to the environment and has adverse effects on the economy and the ecosystem. Oil–water separation and oil waste management require mechanically robust, durable, low-cost, and highly efficient oil–water manipulation systems. To address this challenge superhydrophobic–superoleophilic and superhydrophilic–underwater superoleophobic membrane filters have shown promising results. However, the recyclability and durability issues of such filters are limiting factors in their industrial application, as well as in their use in oil spill accidents. In this article, we review and discuss the recent progress in the application of FS laser surface structuring in producing durable and robust oil–water separation membrane filters. The wide variety of surface structures produced by FS laser nano- and micromachining are initially presented here, while the excellent wetting characteristics shown by specific femtosecond-induced structures are demonstrated. Subsequently, the working principles of oil–water separation membranes are elaborated, and the most recent advances in the topic are analyzed and discussed. Full article

(This article belongs to the Special Issue Ultrafast Laser Pulses)

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15 pages, 3671 KiB

Open AccessReview

Surface Plasmon Nanolaser: Principle, Structure, Characteristics and Applications

by Litu Xu, Fang Li, Yahui Liu, Fuqiang Yao and Shuai Liu

Appl. Sci. 2019, 9(5), 861; https://doi.org/10.3390/app9050861 - 28 Feb 2019

Cited by 25 | Viewed by 6550

Abstract

Photonic devices are becoming more and more miniaturized and highly integrated with the advancement of micro-nano technology and the rapid development of integrated optics. Traditional semiconductor lasers have diffraction limit due to the feedback from the optical system, and their cavity length is [...] Read more.

Photonic devices are becoming more and more miniaturized and highly integrated with the advancement of micro-nano technology and the rapid development of integrated optics. Traditional semiconductor lasers have diffraction limit due to the feedback from the optical system, and their cavity length is more than half of the emission wavelength, so it is difficult to achieve miniaturization. Nanolasers based on surface plasmons can break through the diffraction limit and achieve deep sub-wavelength or even nano-scale laser emission. The improvement of modern nanomaterial preparation processes and the gradual maturity of micro-nano machining technology have also provided technical conditions for the development of sub-wavelength and nano-scale lasers. This paper describes the basic principles of surface plasmons and nano-resonators. The structure and characteristics of several kinds of plasmonic nanolasers are discussed. Finally, the paper looks forward to the application and development trend of nanolasers. Full article

(This article belongs to the Special Issue Ultrafast Laser Pulses)

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Other

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7 pages, 1860 KiB

Open AccessCase Report

Alopecia Totalis Treated with 1064 nm Picosecond Nd:YAG Laser: A Case Report

by Shiow-Jen Juang, Tsung-Hua Tsai, Shu-Hui Wang and Ching-Chi Chi

Appl. Sci. 2019, 9(7), 1298; https://doi.org/10.3390/app9071298 - 28 Mar 2019

Cited by 1 | Viewed by 5329

Abstract

Alopecia areata (AA) is an autoimmune disorder causing nonscarring hair loss. Alopecia totalis (AT), the severe form of AA, is usually refractory to many first-line treatments including topical and intralesional corticosteroids and topical immunotherapy. Systemic corticosteroids, ultraviolet light phototherapy, and immunosuppressants may be [...] Read more.

Alopecia areata (AA) is an autoimmune disorder causing nonscarring hair loss. Alopecia totalis (AT), the severe form of AA, is usually refractory to many first-line treatments including topical and intralesional corticosteroids and topical immunotherapy. Systemic corticosteroids, ultraviolet light phototherapy, and immunosuppressants may be effective but can cause side effects and high recurrence rates after discontinuing treatment. Janus kinase inhibitors and numerous types of lasers, such as 308 nm excimer laser or light, low-level laser therapy, and fractional lasers have been explored for alternative treatment of AA over the past few years with beneficial effects. Herein, we presented a case of AT treated with the novel 1064 nm picosecond Nd:YAG laser (ps-Nd:YAG) (Cutera, Brisbane, CA, USA) under a split-scalp study. A 25-year-old woman presenting with AT for two years was treated with topical and intralesional steroid and the 1064 nm Nd-YAG picosecond laser on the right half of the scalp. The laser treatment interval was once a month. The left half of the scalp was treated with topical and intralesional steroids alone. After treatment for six times, the right half of the scalp had greater improvement than the left half of the scalp. 1064 nm picosecond Nd:YAG laser therapy may be an effective alternative adjuvant treatment for AT. Full article

(This article belongs to the Special Issue Ultrafast Laser Pulses)

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