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9 pages, 547 KiB

Open AccessCommunication

Advantages of Using Hard X-ray Photons for Ultrafast Diffraction Measurements

by Vladimir Lipp, Ichiro Inoue and Beata Ziaja

Photonics 2023, 10(8), 948; https://doi.org/10.3390/photonics10080948 - 18 Aug 2023

Viewed by 1194

Abstract

We present a comparative theoretical study of silicon crystals irradiated with X-ray free-electron laser pulses, using hard X-ray photons of various energies. Simulations are performed with our in-house hybrid code XTANT based on Monte Carlo, Tight Binding and Molecular Dynamics simulation techniques. By [...] Read more.

We present a comparative theoretical study of silicon crystals irradiated with X-ray free-electron laser pulses, using hard X-ray photons of various energies. Simulations are performed with our in-house hybrid code XTANT based on Monte Carlo, Tight Binding and Molecular Dynamics simulation techniques. By comparing the strength of the coherently scattered signal and the corresponding electronic radiation damage for three X-ray photon energies available at the SACLA free-electron laser facility, we conclude that it would be beneficial to use higher photon energies for “diffraction-before-destruction” experiments. Full article

(This article belongs to the Special Issue Lasers and Dynamic of Systems)

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10 pages, 6637 KiB

Open AccessEditor’s ChoiceCommunication

The Effect of Electron Escape Rate on the Nonlinear Dynamics of Quantum Dot Lasers under Optical Feedback

by Qingqing Wang, Zhengmao Wu, Yanfei Zheng and Guangqiong Xia

Photonics 2023, 10(8), 878; https://doi.org/10.3390/photonics10080878 - 28 Jul 2023

Cited by 1 | Viewed by 1187

Abstract

When theoretically investigating the nonlinear dynamics of quantum dot lasers (QDLs), the parameter value of the electron escape rate (C^e) is sometimes approximated to zero to simplify the calculation. However, the value of C^e is dependent on the energy [...] Read more.

When theoretically investigating the nonlinear dynamics of quantum dot lasers (QDLs), the parameter value of the electron escape rate (C^e) is sometimes approximated to zero to simplify the calculation. However, the value of C^e is dependent on the energy interval between the ground state (GS) and the excited state (ES) in the conduction band and is affected by the operation temperature. As a result, such simplified approximation treatments may lead to inaccurate results. In this study, after considering the effect of C^e, we investigate the nonlinear dynamics of QDLs with and without optical feedback based on the asymmetric electron-hole carrier rate equation model. The simulation results show that without optical feedback, the lasing conditions for ES and GS in free-running QDLs are dependent on the value of C^e. A larger C^e is more helpful for the ES emission, and the GS emission will stop lasing if C^e is large enough. Through analyzing the dynamical characteristics of GS and ES in QDLs with optical feedback under different C^e values, it can be found that the dynamical characteristics are strongly correlative with C^e. Full article

(This article belongs to the Special Issue Lasers and Dynamic of Systems)

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11 pages, 2871 KiB

Open AccessFeature PaperArticle

Real-Time Exploration on Buildup Dynamics of Diode-Pumped Passively Mode-Locked Nd:YVO₄ Laser with SESAM

by Pin-Wen Cheng, Yu-Hsin Hsu, Xiu-Wei Chang, Hsing-Chih Liang and Yung-Fu Chen

Photonics 2023, 10(7), 826; https://doi.org/10.3390/photonics10070826 - 15 Jul 2023

Viewed by 1458

Abstract

The buildup dynamics of diode-pumped passively mode-locked solid-state laser is thoroughly explored using the real-time measurement with temporal sampling rate of up to 40 GHz. A concise cavity is developed to ensure the transient dynamics purely arising from the gain medium and saturable [...] Read more.

The buildup dynamics of diode-pumped passively mode-locked solid-state laser is thoroughly explored using the real-time measurement with temporal sampling rate of up to 40 GHz. A concise cavity is developed to ensure the transient dynamics purely arising from the gain medium and saturable absorber. Experimental results reveal that the laser output in the buildup process exhibits numerous passively Q-switched pulses followed with a damped relaxation oscillation prior to the stable mode locking. Furthermore, it is confirmed that the laser output has already displayed single clean mode-locked pulses inside the first several Q-switched envelopes before stepping into the stage of relaxation oscillation. The present real-time exploration is expected to provide important information for practical applications with temporal modulation of the pump intensity. Full article

(This article belongs to the Special Issue Lasers and Dynamic of Systems)

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17 pages, 45939 KiB

Open AccessEditor’s ChoiceArticle

Route to Chaos in a Unidirectional Ring of Three Diffusively Coupled Erbium-Doped Fiber Lasers

by José Octavio Esqueda de la Torre, Juan Hugo García-López, Rider Jaimes-Reátegui, Guillermo Huerta-Cuellar, Vicente Aboites and Alexander N. Pisarchik

Photonics 2023, 10(7), 813; https://doi.org/10.3390/photonics10070813 - 12 Jul 2023

Cited by 7 | Viewed by 1274

Abstract

We numerically investigate the dynamics of a ring consisting of three unidirectionally coupled Erbium-Doped Fiber Lasers (EDLFs) without external pump modulation. The study focuses on the system behavior as the coupling strength is varied, employing a six-dimensional mathematical model that includes three variables [...] Read more.

We numerically investigate the dynamics of a ring consisting of three unidirectionally coupled Erbium-Doped Fiber Lasers (EDLFs) without external pump modulation. The study focuses on the system behavior as the coupling strength is varied, employing a six-dimensional mathematical model that includes three variables for laser intensities and three variables for population inversions of all lasers. Our primary objective is to understand the system evolution towards chaos from a stable equilibrium in the ring, considering the impact of increasing coupling strength. To analyze the system’s behavior, we employ various techniques such as time series analysis, power spectra, Poincaré sections, bifurcation diagrams, and Lyapunov exponents. During the transition to chaos, the system undergoes a Hopf bifurcation and a series of torus bifurcations. An essential aspect of this study is the exploration of a rotating wave propagating along the ring, where the wave nature (periodic, quasiperiodic, or chaotic) depends on the coupling strength. Additionally, we observe the coexistence of periodic and chaotic orbits within a specific range of the coupling strength. However, for very strong coupling, this bistability disappears, resulting in a monostable system with a single limit cycle. This regime exhibits potential for applications that demand short laser pulses with a substantial increase in peak power, reaching nearly 20 times higher levels compared to the continuous mode when the lasers are uncoupled. This discovery holds particular importance for optical communication systems, especially considering the attenuation optical signals experience when transmitted over long distances. Full article

(This article belongs to the Special Issue Lasers and Dynamic of Systems)

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12 pages, 2104 KiB

Open AccessArticle

The Influence of Gadolinium Oxide Nanoparticles Concentration on the Chemical and Physical Processes Intensity during Laser-Induced Breakdown of Aqueous Solutions

by Aleksander V. Simakin, Ilya V. Baimler, Alexey S. Baryshev, Anastasiya O. Dikovskaya and Sergey V. Gudkov

Photonics 2023, 10(7), 784; https://doi.org/10.3390/photonics10070784 - 5 Jul 2023

Cited by 3 | Viewed by 1330

Abstract

The paper investigates the physicochemical processes that occur during laser-induced breakdown in colloids of gadolinium oxide nanoparticles of different concentrations. A monotonic change in the number of optical breakdowns, the average distance between the nearest breakdowns in the track of a single laser [...] Read more.

The paper investigates the physicochemical processes that occur during laser-induced breakdown in colloids of gadolinium oxide nanoparticles of different concentrations. A monotonic change in the number of optical breakdowns, the average distance between the nearest breakdowns in the track of a single laser pulse, the average plasma size of a single optical breakdown, the integral luminosity of an optical breakdown plasma flash, the intensity of acoustic signals, and the rate of formation of dissociation products—O₂, H₂, OH^•, and H₂O₂—is demonstrated. It is shown that the rate of formation of chemical products of the decomposition of H₂O molecules under the action of breakdown when using nanoparticles of rare earth metals, in particular, gadolinium oxide, is the highest compared to other materials. Based on one laser pulse, the rates of formation of chemical products formed during the dissociation of water during laser-induced breakdown of a colloid of gadolinium oxide nanoparticles are 13.13 nmol/pulse for H₂, 5.41 nmol/pulse for O₂, and 6.98 nmol/pulse for hydrogen peroxide. Full article

(This article belongs to the Special Issue Lasers and Dynamic of Systems)

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8 pages, 7432 KiB

Open AccessCommunication

Investigation of the Process of Evolution of Traces of Explosives Carried by Fingerprints Using Polarimetric Macrophotography and Remote LF/LIF Method

by Sergei Bobrovnikov, Evgeny Gorlov, Viktor Zharkov, Sergei Murashko, Alexander Vorozhtsov and Alexander Stykon

Photonics 2023, 10(7), 740; https://doi.org/10.3390/photonics10070740 - 28 Jun 2023

Viewed by 990

Abstract

The results of a study of the degradation of the cyclotrimethylenetrinitramine (RDX) traces carried in fingerprints depending on the fingerprint number are presented. The surface concentration of the trace was assessed using macrophotography in polarized light and by the method of laser fragmentation/laser-induced [...] Read more.

The results of a study of the degradation of the cyclotrimethylenetrinitramine (RDX) traces carried in fingerprints depending on the fingerprint number are presented. The surface concentration of the trace was assessed using macrophotography in polarized light and by the method of laser fragmentation/laser-induced fluorescence. A technique for estimating the surface concentration of RDX traces in sweat-fat fingerprints based on pixel-by-pixel scanning of macrophotographs is described. The data of parallel experiments on remote laser detection of RDX particles in fingerprints are presented. A comparison shows that the results of the direct measurements of the total trace area are in good agreement with the LF/LIF response data. Full article

(This article belongs to the Special Issue Lasers and Dynamic of Systems)

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13 pages, 3340 KiB

Open AccessArticle

Temperature-Dependent Optical Properties of Bismuth Triborate Crystal in the Terahertz Range: Simulation of Terahertz Generation by Collinear Three-Wave Mixing in the Main Crystal Planes

by Dmitry Ezhov, Nazar Nikolaev, Valery Antsygin, Sofia Bychkova, Yury Andreev and Valery Svetlichnyi

Photonics 2023, 10(7), 713; https://doi.org/10.3390/photonics10070713 - 22 Jun 2023

Cited by 2 | Viewed by 1371

Abstract

Terahertz (THz) frequency generation via nonlinear optical techniques is of particular interest due to the immense potential of this type of radiation in various scientific fields, ranging from medicine to telecommunications. Selecting suitable nonlinear media for laser frequency down-conversion presents a challenging task. [...] Read more.

Terahertz (THz) frequency generation via nonlinear optical techniques is of particular interest due to the immense potential of this type of radiation in various scientific fields, ranging from medicine to telecommunications. Selecting suitable nonlinear media for laser frequency down-conversion presents a challenging task. Considering an approach that uses nonlinear crystals with high radiation resistance, pumped by intense laser pulses near their damage threshold, we suggest the crystal of bismuth triborate (BiB₃O₆, BIBO). Compared to other borate-class crystals, BIBO exhibits relatively high coefficients of quadratic susceptibility. In this paper, we have studied the optical properties of BIBO samples in a wide spectral range from 0.1 to 2.1 THz at temperatures of 473, 383, 295, and 77 K using Terahertz Time-Domain Spectroscopy (THz-TDS). Furthermore, we simulated collinear three-wave interactions with nonzero efficiency for difference frequency generation (DFG) in the THz range. For the pump wavelengths of about 800 nm, we determined phase-matching (PM) conditions and compared the generation efficiency for different crystal cuts. The potential of utilizing BIBO crystal for terahertz frequency generation is discussed. Full article

(This article belongs to the Special Issue Lasers and Dynamic of Systems)

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12 pages, 7051 KiB

Open AccessArticle

Segmented Four-Element Photodiodes in a Three-Dimensional Laser Beam Angle Measurement

by Stanislav Konov, Aleksander Frolov, Petr Shapovalov, Pavel Peretyagin and Sergey Grigoriev

Photonics 2023, 10(7), 704; https://doi.org/10.3390/photonics10070704 - 21 Jun 2023

Cited by 1 | Viewed by 1245

Abstract

Based on the registration of two laser beam projections, a method for measuring the angular deviation of a laser beam from its initial position in three-dimensional space is proposed and experimentally demonstrated. The laser ray is directed into the beam-splitting cube, which distributes [...] Read more.

Based on the registration of two laser beam projections, a method for measuring the angular deviation of a laser beam from its initial position in three-dimensional space is proposed and experimentally demonstrated. The laser ray is directed into the beam-splitting cube, which distributes the ray into two mutually orthogonal parts, on the path of which, two four-segment photodiodes are located at different distances from the beam-splitting cube. The value of the angular deviation from a certain initial position of the laser beam in three-dimensional space is obtained after the mathematical processing of the measured position of the laser beam projections’ centers in the photodiodes coordinates systems. The innovation of this method is that the resulting angular deviation of the laser beam is in three-dimensional space due to the registration of a pair of projections. The experimental results also demonstrate that the proposed method has a high speed-measuring potential and can be used for solving a wide range of problems. Full article

(This article belongs to the Special Issue Lasers and Dynamic of Systems)

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14 pages, 7296 KiB

Open AccessArticle

Seven-Grooved-Rod, Side-Pumping Concept for Highly Efficient TEM₀₀-Mode Solar Laser Emission through Fresnel Lenses

by Hugo Costa, Dawei Liang, Joana Almeida, Miguel Catela, Dário Garcia, Bruno D. Tibúrcio and Cláudia R. Vistas

Photonics 2023, 10(6), 620; https://doi.org/10.3390/photonics10060620 - 26 May 2023

Cited by 4 | Viewed by 1099

Abstract

Low-cost, lightweight, and easily available Fresnel lenses are a more alluring choice for solar laser power production, when compared to the costly and complex heliostat-parabolic mirror systems. Therefore, a seven-rod solar laser head was designed and numerically studied to enhance the efficiency in [...] Read more.

Low-cost, lightweight, and easily available Fresnel lenses are a more alluring choice for solar laser power production, when compared to the costly and complex heliostat-parabolic mirror systems. Therefore, a seven-rod solar laser head was designed and numerically studied to enhance the efficiency in TEM₀₀-mode laser power production, employing six Fresnel lenses with 10 m² total collection area for collection and concentration of sunlight. Six folding mirrors redirected the solar rays towards the laser head, composed of six fused silica aspheric lenses and rectangular compound parabolic concentrators paired together for further concentration, and a cylindrical cavity, in which seven Nd:YAG rods were mounted and side-pumped. With conventional rods, total TEM₀₀-mode laser power reached 139.89 W, which is equivalent to 13.99 W/m² collection efficiency and 1.47% solar-to-TEM₀₀-mode laser power conversion efficiency. More importantly, by implementing rods with grooved sidewalls, the total laser power was increased to 153.29 W, corresponding to 15.33 W/m² collection and 1.61% conversion efficiencies. The side-pumping configuration and the good thermal performance may ensure that the seven-grooved-rod system has better scalability than other previously proposed schemes. Full article

(This article belongs to the Special Issue Lasers and Dynamic of Systems)

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6 pages, 1848 KiB

Open AccessCommunication

Alexandrite and Nd:YAG Laser vs. IPL in the Management of Facial Hirsutism: A Retrospective Study

by Elena Zappia, Serena Federico, Carmen Volpe, Elisabetta Scali, Steven Paul Nisticò and Luigi Bennardo

Photonics 2023, 10(5), 572; https://doi.org/10.3390/photonics10050572 - 14 May 2023

Viewed by 5631

Abstract

Background and objectives: Hirsutism is characterized by the abnormal presence of hair in women, which occurs in typically male areas. The causes of this symptom can be many; however, it is often associated with PCOS. Among the most effective procedures that can be [...] Read more.

Background and objectives: Hirsutism is characterized by the abnormal presence of hair in women, which occurs in typically male areas. The causes of this symptom can be many; however, it is often associated with PCOS. Among the most effective procedures that can be used for hair removal are lasers such as the Alex laser, Nd: YAG, and IPL. Materials and Methods: This study analyzed a total of 71 patients who were treated for hirsutism caused mainly by PCOS; the remaining cases were idiopathic. The patients were divided into two groups: the first group was treated with laser sources, specifically Alex and Nd: YAG, and the second group underwent treatment with IPL. The results were evaluated six months after the last treatment. Results: Out of 71 treated patients, all patients experienced good or excellent hair reduction with greater efficacy in laser-treated patients. The incidence of side effects was low, particularly in the IPL group. Conclusions: Both laser and IPL are efficient, safe, and tolerable procedures in treating PCOS-related and idiopathic facial hirsutism, and both have been shown to have a low rate of side effects. However, the Alex and Nd: YAG lasers guaranteed better hair removal results. A more extensive clinical study will be necessary to confirm our study’s results. Full article

(This article belongs to the Special Issue Lasers and Dynamic of Systems)

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12 pages, 2361 KiB

Open AccessArticle

Temperature Changes during Er:YAG Laser Activation with the Side-Firing Spiral Endo Tip in Root Canal Treatment

by Sharonit Sahar-Helft, Nathanyel Sebbane, Adi Farber, Ronit Vogt Sionov, Roni Dakar and Doron Steinberg

Photonics 2023, 10(5), 488; https://doi.org/10.3390/photonics10050488 - 24 Apr 2023

Viewed by 1835

Abstract

Erbium-doped yttrium aluminum garnet (Er:YAG) laser-activated irrigation (LAI) is used in endodontic treatment to remove the smear layer and kill bacteria in the root canal. However, this procedure can cause photo-thermal effects that harm the surrounding tissue. Therefore, it was important to study [...] Read more.

Erbium-doped yttrium aluminum garnet (Er:YAG) laser-activated irrigation (LAI) is used in endodontic treatment to remove the smear layer and kill bacteria in the root canal. However, this procedure can cause photo-thermal effects that harm the surrounding tissue. Therefore, it was important to study the temperature changes that occur at the outer tooth surface during activation of the Er:YAG laser using a side-firing spiral Endo tip in the root canal. Laser treatment was performed either in the absence of fluid in the root canal or in the presence of a 17% EDTA solution. Irrigation with 17% EDTA was either performed in a continuous mode for 60 s or in a segmented mode of 4 rinses with 17% EDTA for 15 s each. The temperature was measured every second during the treatment at three tooth surface sites: the cementoenamel junction, the middle region and the apical region. Our data show that the greatest temperature changes occurred when the laser was used alone without an irrigation solution, while minor temperature changes were observed with continuous irrigation. In conclusion, we would recommend applying the laser treatment with an irrigation solution to avoid excessive heating. Full article

(This article belongs to the Special Issue Lasers and Dynamic of Systems)

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14 pages, 2037 KiB

Open AccessArticle

High Efficiency and High Stability for SHG in an Nd:YVO₄ Laser with a KTP Intracavity and Q-Switching through Harmonic Modulation

by Samuel Mardoqueo Afanador Delgado, Juan Hugo García López, Rider Jaimes Reátegui, Vicente Aboites, José Luis Echenausía Monroy and Guillermo Huerta Cuellar

Photonics 2023, 10(4), 454; https://doi.org/10.3390/photonics10040454 - 14 Apr 2023

Cited by 2 | Viewed by 2183

Abstract

In this paper, the stabilization and high efficiency of an unstable Second Harmonic Generation (SHG) of an

N d : Y V O_{4}

laser with a KTP intracavity is demonstrated. By using a passive Q-switching crystal ( [...] Read more.

In this paper, the stabilization and high efficiency of an unstable Second Harmonic Generation (SHG) of an

N d : Y V O_{4}

laser with a KTP intracavity is demonstrated. By using a passive Q-switching crystal (

C r^{4 +} : Y A G

) and a parametric modulation method (harmonic modulation), the stabilization of the laser is reached. An harmonic modulation was applied to the pumping of the

N d : Y V O_{4}

-KTP laser to control the amplitude and frequency of the laser emission. The results were characterized by using power spectra analysis, optical spectrum, bifurcation diagrams, and temporal series of the laser intensity. The promising application of this green light source is materialized when such light is necessary for high-density optics, such as in the treatment materials industry or in some aesthetic applications. Full article

(This article belongs to the Special Issue Lasers and Dynamic of Systems)

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13 pages, 1099 KiB

Open AccessArticle

Comparison of Raman Spectra of Optically Nonlinear LiTaO₃:Cr³⁺ (0.005 wt%) Crystal Laser Excited in Visible (532 nm) and Near-IR (785 nm) Areas

by Mikhail Palatnikov, Nikolay Sidorov, Alexander Pyatyshev and Alexander Skrabatun

Photonics 2023, 10(4), 439; https://doi.org/10.3390/photonics10040439 - 12 Apr 2023

Cited by 2 | Viewed by 1671

Abstract

Raman spectra have been excited by the radiation of lasers generatingon in the visible (532 nm) and near-IR (785 nm) ranges in a LiTaO₃:Cr³⁺ (0.005 wt%) crystal. The obtained spectra were compared. Recorded Raman spectra contained bands in the range [...] Read more.

Raman spectra have been excited by the radiation of lasers generatingon in the visible (532 nm) and near-IR (785 nm) ranges in a LiTaO₃:Cr³⁺ (0.005 wt%) crystal. The obtained spectra were compared. Recorded Raman spectra contained bands in the range of <900 cm⁻¹ (first order) up to 2000 cm⁻¹ (second order). The Raman spectra of the second order, excited by near-IR laser radiation, were located against the background of a wide, luminescent halo. The frequency of a single low-intensity band exceeded the exact frequency of an overtone corresponding to the completely symmetric fundamental 4A₁(z)LO mode. The attribution of other second-order bands with higher frequencies remains unclear. Full article

(This article belongs to the Special Issue Lasers and Dynamic of Systems)

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11 pages, 1497 KiB

Open AccessCommunication

Coupling of Photonic and Plasmonic Modes for Double Nanowire Cavities

by Xuanran Peng, Jing Liu, Yaru Kang, Xu Mao, Wei Yan, Xiaohui Wang, Kong Liu, Rui Xu, Fuhua Yang and Zhaofeng Li

Photonics 2023, 10(4), 415; https://doi.org/10.3390/photonics10040415 - 6 Apr 2023

Cited by 1 | Viewed by 1694

Abstract

We analyze the coupling between double nanowire cavities for both photonic modes and plasmonic modes. When the spacing between nanowires reduces, a redshift of the resonant frequency of the symmetric mode and a blueshift of the resonant frequency of the antisymmetric mode are [...] Read more.

We analyze the coupling between double nanowire cavities for both photonic modes and plasmonic modes. When the spacing between nanowires reduces, a redshift of the resonant frequency of the symmetric mode and a blueshift of the resonant frequency of the antisymmetric mode are observed. Compared to single nanowire cavity modes, the Q factors of antisymmetric supermodes of double nanowires can be improved by 51% for photonic modes and by 24% for plasmonic modes. The mechanisms of Q factor improvement for photonic modes and plasmonic modes are studied based on the field distribution of radiations from the modes. This paper may contribute to research and applications for double nanowire lasers and nanowire laser arrays. Full article

(This article belongs to the Special Issue Lasers and Dynamic of Systems)

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9 pages, 5383 KiB

Open AccessCommunication

Multi-Bessel Beams Generated by an Axicon and a Spatial Light Modulator for Drilling Applications

by Christian Lutz, Simon Schwarz, Jan Marx, Cemal Esen and Ralf Hellmann

Photonics 2023, 10(4), 413; https://doi.org/10.3390/photonics10040413 - 6 Apr 2023

Cited by 10 | Viewed by 2450

Abstract

We report on an optical setup to generate multi-Bessel beam profiles combining a refractive axicon and a spatial light modulator. Based on their particular beam profile, Bessel beams offer advantageous properties for micro drilling processes and internal volume processing, especially for transparent materials. [...] Read more.

We report on an optical setup to generate multi-Bessel beam profiles combining a refractive axicon and a spatial light modulator. Based on their particular beam profile, Bessel beams offer advantageous properties for micro drilling processes and internal volume processing, especially for transparent materials. In addition, the laser power of industrial, ultrashort pulsed lasers has increased significantly over the last few years, offering the possibility for highly efficient processes using multi-spot profiles. Our optical concept combines the dynamic possibilities of beam splitting using a spatial light modulator with the benefits of Bessel beams, which facilitates multi-Bessel beam processing. Beside the simulation and experimental evaluation of the generated multi-Bessel beams, we exemplify the applicability of the developed module for the perforation of thin metal foils by micro drilling. Full article

(This article belongs to the Special Issue Lasers and Dynamic of Systems)

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15 pages, 4217 KiB

Open AccessArticle

CO₂ and Diode Lasers vs. Conventional Surgery in the Disinclusion of Palatally Impacted Canines: A Randomized Controlled Trial

by Alessandra Impellizzeri, Martina Horodynski, Gaspare Palaia, Gerardo La Monaca, Daniele Pergolini, Antonella Polimeni, Umberto Romeo and Gabriella Galluccio

Photonics 2023, 10(3), 244; https://doi.org/10.3390/photonics10030244 - 23 Feb 2023

Cited by 2 | Viewed by 2166

Abstract

Background: The aim of this RCT is to show the effectiveness of laser technology for the exposure of palatally impacted canines, using a CO₂ or diode laser, and to evaluate the possible bio-stimulation effect of the laser on the spontaneous eruption of [...] Read more.

Background: The aim of this RCT is to show the effectiveness of laser technology for the exposure of palatally impacted canines, using a CO₂ or diode laser, and to evaluate the possible bio-stimulation effect of the laser on the spontaneous eruption of the canine. Methods: This study was carried out on a sample of 27 patients, divided randomly into three groups: treated with a CO₂ laser (Group A), treated with a diode laser (Group B), and treated with a cold blade (Group C). Monitoring was performed at 1, 8, and 16 weeks after surgery, through photo and digital scans performed with a CS3500 intraoral scanner. Results: It was found that the average total eruptions are 4.55 mm for Group A, 5.36 mm for Group B, and 3.01 mm for Group C. The difference in eruption between groups A and B is not significant. Comparing the laser groups with the control group, it has emerged that the difference in eruption is statistically significant. Conclusion: A significant tooth movement was observed in both Groups A and B. The response of the canine to the bio-stimulation of the laser can be considered effective, resulting in a statistically significant difference between the study groups and the control group. Both lasers have the same bio-stimulatory action on the eruption of canines. Full article

(This article belongs to the Special Issue Lasers and Dynamic of Systems)

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10 pages, 2997 KiB

Open AccessCommunication

Simultaneous Manipulation of the Temporal and Spatial Behaviors of Nanosecond Laser Based on Hybrid Q-Switching

by Haoxi Yang, Yuanji Li, Wenrong Wang, Jinxia Feng and Kuanshou Zhang

Photonics 2023, 10(2), 227; https://doi.org/10.3390/photonics10020227 - 20 Feb 2023

Viewed by 1745

Abstract

A hybrid Q-switching method based on a special-shaped saturated absorber was proposed for simultaneous manipulation of the temporal and spatial behaviors of a solid-state pulse laser. The temporal–spatial rate equation model of the laser was given and used to optimize the design parameter [...] Read more.

A hybrid Q-switching method based on a special-shaped saturated absorber was proposed for simultaneous manipulation of the temporal and spatial behaviors of a solid-state pulse laser. The temporal–spatial rate equation model of the laser was given and used to optimize the design parameter of the saturated absorber. Best spatial intensity homogenization performance can be expected using an active-passive hybrid Q-switched laser, comprising a Pockels cell and a cylinder Cr:YAG crystal with one end cut as a spherical concave surface. The optimized laser pulse width could be narrowed to 2.39 ns and the laser radial intensity distribution became quasi-super-Gaussian distribution with a radial intensity distribution ratio of 0.91, while that for the Gaussian beam was 0.84. In principle, the laser coherence can be maintained, and the laser spatial intensity distribution can be kept in a long propagation distance. Full article

(This article belongs to the Special Issue Lasers and Dynamic of Systems)

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9 pages, 1678 KiB

Open AccessCommunication

Generalized Poincaré Beams in Tight Focus

by Victor V. Kotlyar, Alexey A. Kovalev and Alexey M. Telegin

Photonics 2023, 10(2), 218; https://doi.org/10.3390/photonics10020218 - 16 Feb 2023

Cited by 3 | Viewed by 1523

Abstract

We study the tight focus of generalized (hybrid) Poincaré beams. A conventional Poincaré beam is a coaxial superposition of two optical vortices, one with left circular polarization and a topological charge (TC) of m, while the other has a right circular polarization [...] Read more.

We study the tight focus of generalized (hybrid) Poincaré beams. A conventional Poincaré beam is a coaxial superposition of two optical vortices, one with left circular polarization and a topological charge (TC) of m, while the other has a right circular polarization and a TC of −m. The generalized Poincaré beams are also composed of two optical vortices, but their TCs are different, for instance, p and q. Here, we theoretically investigate the generalized Poincaré beams with the TCs p = m + 1 and q = −m in tight focus. In this case, both transverse components of the strength vector of the initial electric field have a topological charge of 1/2, and the beam itself is a cylindrical vector beam of fractional order m + 1/2. Analytical expressions are derived for the components of the strength vectors of the electric and magnetic field at the focus as well as for the intensity distribution, the longitudinal component of the spin angular momentum (SAM), and for the components of the Poynting vector (energy flow density). We show that the intensity at the focus has 2m − 1 local maxima residing evenly in a certain circle radius with the center on the optical axis. We also demonstrate that the radial spin and orbital Hall effects occur at the focus, i.e., the longitudinal SAM component has different signs in the circles of different radii, and the azimuthal component of the transverse Poynting vector also has different signs. Full article

(This article belongs to the Special Issue Lasers and Dynamic of Systems)

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13 pages, 4839 KiB

Open AccessArticle

A Tunable Optoelectronic Oscillator with Phase-to-Amplitude Modulation Transformation via an Acetylene Reference Cell

by Vladimir Lebedev, Piotr Agruzov, Igor’ Iliyechev, Andrei Varlamov, Ivan Tatsenko, Andrey Nikitin, Alexey B. Ustinov, Serguei Stepanov and Alexander Shamray

Photonics 2023, 10(2), 196; https://doi.org/10.3390/photonics10020196 - 12 Feb 2023

Cited by 1 | Viewed by 1509

Abstract

Operation modes of the optoelectronic oscillator (OEO), based on a phase electrooptic modulator with an acetylene reference cell as a photonic filter, have been investigated. For the wideband phase-to-amplitude demodulation that was observed when the laser wavelength was tuned to one side of [...] Read more.

Operation modes of the optoelectronic oscillator (OEO), based on a phase electrooptic modulator with an acetylene reference cell as a photonic filter, have been investigated. For the wideband phase-to-amplitude demodulation that was observed when the laser wavelength was tuned to one side of the acetylene absorption line, an additional tunable electronic yttrium iron garnet (YIG) filter was introduced to observe single-mode OEO generation. This configuration generated a stable monochromatic signal in the 4–12 GHz frequency range, with phase noise of −122 dBc/Hz at 10 kHz offset from the carrier frequency. In the narrowband demodulation mode (when one optical modulation sideband was tuned to the acetylene absorption line), the quasi-single-mode oscillation could be observed without additional electronic filtering. In this case, the generation frequency was controlled optically by tuning the laser wavelength. Full article

(This article belongs to the Special Issue Lasers and Dynamic of Systems)

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14 pages, 4246 KiB

Open AccessCommunication

Statistical Mixture of Kaleidoscope States Interacting with a Two-Level Atom: Entropy and Purification

by Jorge A. Anaya-Contreras, Arturo Zúñiga-Segundo and Héctor M. Moya-Cessa

Photonics 2023, 10(2), 150; https://doi.org/10.3390/photonics10020150 - 31 Jan 2023

Viewed by 1537

Abstract

We investigate some of the fundamental features of the interaction of a mixture of coherent states, namely, a Kaleidoscope states mixture, with two-level atoms in the Jaynes–Cummings model framework. We begin our analysis by calculating the von Neumann entropy of the field, which [...] Read more.

We investigate some of the fundamental features of the interaction of a mixture of coherent states, namely, a Kaleidoscope states mixture, with two-level atoms in the Jaynes–Cummings model framework. We begin our analysis by calculating the von Neumann entropy of the field, which is determined with the help of the virtual atom method. The oscillations appearing in the entropy indicate a state of purity greater than the initial state, i.e., a purification of the initial state due to a transfer of coherence from the atom to the field. In this oscillatory region, we obtain a negative Wigner function that hints at a (noisy) multiple Schrödinger cat. Full article

(This article belongs to the Special Issue Lasers and Dynamic of Systems)

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9 pages, 4419 KiB

Open AccessArticle

Flexible, Stretchable, Tunable, and Switchable DFB Laser

by Daniele Eugenio Lucchetta, Andrea Di Donato, Oriano Francescangeli, Cristiano Riminesi, Gautam Singh and Riccardo Castagna

Photonics 2023, 10(1), 12; https://doi.org/10.3390/photonics10010012 - 23 Dec 2022

Cited by 1 | Viewed by 1796

Abstract

We are reporting on easily-made, flexible, wearable, and stretchable holographic gratings for tunable distributed-feedback lasers. The laser device is formed by the integration of a reflection volume phase grating in a flexible substrate. The grating is recorded in a photopolymerizable mixture by using [...] Read more.

We are reporting on easily-made, flexible, wearable, and stretchable holographic gratings for tunable distributed-feedback lasers. The laser device is formed by the integration of a reflection volume phase grating in a flexible substrate. The grating is recorded in a photopolymerizable mixture by using optical holography. The photopolymerizing material is a new compound derived from a recently developed mixture which is based largely on haloalkanes and acrylates. An appropriate choice of photoinitiators promotes the photoactivation of the monomers at the writing wavelength of 460 nm. The laser device has a low emission threshold due to the high efficiency of the photopolymerization process at 460 nm. Finally, the amplified spontaneous emission of the device can be continuously tuned by simply bending the film. This peculiarity is promising for the manufacturing of optical pumped tunable organic lasers and flexible displays. Full article

(This article belongs to the Special Issue Lasers and Dynamic of Systems)

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14 pages, 2193 KiB

Open AccessArticle

Implementation of Logic Gates in an Erbium-Doped Fiber Laser (EDFL): Numerical and Experimental Analysis

by Samuel Mardoqueo Afanador Delgado, José Luis Echenausía Monroy, Guillermo Huerta Cuellar, Juan Hugo García López and Rider Jaimes Reátegui

Photonics 2022, 9(12), 977; https://doi.org/10.3390/photonics9120977 - 12 Dec 2022

Cited by 2 | Viewed by 1799

Abstract

At a time when miniaturization and optimization of resources are in the foreground, the development of devices that can perform various functions is a primary goal of technological development. In this work, the use of an Erbium-Doped Fiber Laser (EDFL) is proposed as [...] Read more.

At a time when miniaturization and optimization of resources are in the foreground, the development of devices that can perform various functions is a primary goal of technological development. In this work, the use of an Erbium-Doped Fiber Laser (EDFL) is proposed as a basic system for the generation of an optical logic gate. Taking advantage of the dynamic richness of this type of laser and its use in telecommunication systems, the dynamic response is analyzed when the system is perturbed by a digital signal. The emission response of the system is controlled by the intensity of the digital signal, so that it is possible to obtain different logic operations. The numerical results are in good agreement with the experimental observations. The presented work raises new aspects in the use of chaotic systems as a means of obtaining optical logic gates. Full article

(This article belongs to the Special Issue Lasers and Dynamic of Systems)

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Review

Jump to: Research, Other

19 pages, 810 KiB

Open AccessReview

Evolving Role of Lasers in Endourology: Past, Present and Future of Lasers

by Clara Cerrato, Victoria Jahrreiss, Carlotta Nedbal, Amelia Pietropaolo and Bhaskar Somani

Photonics 2023, 10(6), 635; https://doi.org/10.3390/photonics10060635 - 31 May 2023

Cited by 4 | Viewed by 2914

Abstract

The use of lasers in endourology has grown exponentially, leading to technological advancement and to miniaturization of the procedures. We aim to provide an overview of the lasers used in endourology and the associated future perspectives. Using MEDLINE, a non-systematic review was performed [...] Read more.

The use of lasers in endourology has grown exponentially, leading to technological advancement and to miniaturization of the procedures. We aim to provide an overview of the lasers used in endourology and the associated future perspectives. Using MEDLINE, a non-systematic review was performed including articles between 2006 and 2023. English language original articles, reviews and editorials were selected based on their clinical relevance. Guidelines recommend ureteroscopy in case of stones <2 cm and a percutaneous approach for renal stones ≥2 cm. High-power holmium (Ho:YAG) lasers and the new thulium fibre laser (TFL) may change the future, offering shorter procedures for complex stones, with good outcomes. Increased intrarenal temperature associated with these new technologies may be overcome with adaptive strategies and optimal settings. For upper-tract urothelial carcinoma (UTUC), the combination of laser techniques and these new lasers may reduce the risk of stenosis and allow for a more accurate tumour ablation, potentially reducing the recurrence rates. Laser enucleation procedures are gaining a major role in benign prostate enlargement (BPE), especially in patients with larger prostates or under anticoagulant therapy. However, the superiority of one laser over the other has not been established yet, and the choice of technique is mainly deferred to the surgeon’s expertise. In conclusion, lasers will further expand their horizon in endourology, allowing for instrument adaptation to challenging anatomy. Prospective, randomized clinical trials are however needed to confirm available results and to provide the optimal settings for each pathology. Full article

(This article belongs to the Special Issue Lasers and Dynamic of Systems)

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Other

Jump to: Research, Review

20 pages, 2199 KiB

Open AccessSystematic Review

Therapeutic and Adverse Effects of Lasers in Dentistry: A Systematic Review

by Giuseppina Malcangi, Assunta Patano, Irma Trilli, Fabio Piras, Anna Maria Ciocia, Alessio Danilo Inchingolo, Antonio Mancini, Denisa Hazballa, Daniela Di Venere, Francesco Inchingolo, Elisabetta de Ruvo, Gianna Dipalma and Angelo Michele Inchingolo

Photonics 2023, 10(6), 650; https://doi.org/10.3390/photonics10060650 - 5 Jun 2023

Cited by 11 | Viewed by 8421

Abstract

Laser therapy has become one of the gold standards of treatment in routine dentistry. In the 1970s, CO2 lasers were the first lasers to be used in oral surgery on soft tissues. Subsequently, other lasers (Diode, Nd YAG, Er: YAG, Argon and Erbium) [...] Read more.

Laser therapy has become one of the gold standards of treatment in routine dentistry. In the 1970s, CO2 lasers were the first lasers to be used in oral surgery on soft tissues. Subsequently, other lasers (Diode, Nd YAG, Er: YAG, Argon and Erbium) have also been used in periodontics, implantology, orthodontics and restorative dentistry, as well as for hard tissues, such as bone, enamel and dentin. The purpose of this systematic review is to analyze both the therapeutic properties and adverse effects of laser use in dentistry, related to a non-targeted choice of medical device based on clinical need as well as an inadequate learning curve. A systematic review was performed following the PRISMA guidelines using Pubmed, Scopus and Web of Science. The use of lasers requires a specific learning curve modifying the standard surgical approach. The use of lasers provides multiple therapeutic benefits but can lead to some failures in dental treatments. In restorative dentistry, it has been found that lasers can cause cracks that can lead to fractures and/or affect the composite restoration. In periodontal treatments, the use of lasers can produce thermal damage to pulp tissue. In surgical treatments, the use of a laser caused bleeding, post-operative pain and a burning sensation. The failure of tissue cooling during laser beam emission could produce the necrosis of hard and soft tissues. Full article

(This article belongs to the Special Issue Lasers and Dynamic of Systems)

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