Special Issue "Lasers and Dynamic of Systems"

A special issue of Photonics (ISSN 2304-6732). This special issue belongs to the section "Lasers, Light Sources and Sensors".

Deadline for manuscript submissions: closed (20 July 2023) | Viewed by 23752

Special Issue Editors

Centro de Investigaciones en Optica, A.C., Leon, Mexico
Interests: laser physics; system dynamics and stability; opto-electronic devices
Centro Universitario de los Lagos, Universidad de Guadalajara, Guadalajara, Mexico
Interests: numerical study of laser synapse
Centro Universitario de los Lagos, Universidad de Guadalajara, Guadalajara, Mexico
Interests: dynamic systems

Special Issue Information

Dear Colleagues,

Continuous development in lasers and their applications and interaction with system dynamics justifies its study, due to its contribution to multiple applications. In recent years, a growing research interest in disruptive technologies has arisen, and it is expected that this Special Issue will bring together new proposals in the direction of Lasers and the Dynamics of Systems, yielding innovative discoveries that will lead to potential future applications.

Widely studied lasers have contributed to the growth of other disciplines. Hopefully, this Special Issue will attract cutting-edge research that is reported on highlights from original investigations. This space will therefore serve as a platform for new designs and for developments in lasers and dynamic systems, as well as in other disciplines related to the topic of novel applications.

Prof. Dr. Vicente Aboites, FInstP
Prof. Dr. Juán Hugo García
Prof. Dr. Rider Jaimes-Reategui
Guest Editors

Manuscript Submission Information

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Keywords

  • lasers
  • dynamic systems

Published Papers (24 papers)

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9 pages, 547 KiB  
Communication
Advantages of Using Hard X-ray Photons for Ultrafast Diffraction Measurements
Photonics 2023, 10(8), 948; https://doi.org/10.3390/photonics10080948 - 18 Aug 2023
Viewed by 568
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  
Communication
The Effect of Electron Escape Rate on the Nonlinear Dynamics of Quantum Dot Lasers under Optical Feedback
Photonics 2023, 10(8), 878; https://doi.org/10.3390/photonics10080878 - 28 Jul 2023
Viewed by 497
Abstract
When theoretically investigating the nonlinear dynamics of quantum dot lasers (QDLs), the parameter value of the electron escape rate (Ce) is sometimes approximated to zero to simplify the calculation. However, the value of Ce 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 (Ce) is sometimes approximated to zero to simplify the calculation. However, the value of Ce 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 Ce, 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 Ce. A larger Ce is more helpful for the ES emission, and the GS emission will stop lasing if Ce is large enough. Through analyzing the dynamical characteristics of GS and ES in QDLs with optical feedback under different Ce values, it can be found that the dynamical characteristics are strongly correlative with Ce. Full article
(This article belongs to the Special Issue Lasers and Dynamic of Systems)
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11 pages, 2871 KiB  
Article
Real-Time Exploration on Buildup Dynamics of Diode-Pumped Passively Mode-Locked Nd:YVO4 Laser with SESAM
Photonics 2023, 10(7), 826; https://doi.org/10.3390/photonics10070826 - 15 Jul 2023
Viewed by 537
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  
Article
Route to Chaos in a Unidirectional Ring of Three Diffusively Coupled Erbium-Doped Fiber Lasers
Photonics 2023, 10(7), 813; https://doi.org/10.3390/photonics10070813 - 12 Jul 2023
Cited by 2 | Viewed by 467
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  
Article
The Influence of Gadolinium Oxide Nanoparticles Concentration on the Chemical and Physical Processes Intensity during Laser-Induced Breakdown of Aqueous Solutions
Photonics 2023, 10(7), 784; https://doi.org/10.3390/photonics10070784 - 05 Jul 2023
Viewed by 619
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  
Communication
Investigation of the Process of Evolution of Traces of Explosives Carried by Fingerprints Using Polarimetric Macrophotography and Remote LF/LIF Method
Photonics 2023, 10(7), 740; https://doi.org/10.3390/photonics10070740 - 28 Jun 2023
Viewed by 538
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  
Article
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
Photonics 2023, 10(7), 713; https://doi.org/10.3390/photonics10070713 - 22 Jun 2023
Viewed by 580
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  
Article
Segmented Four-Element Photodiodes in a Three-Dimensional Laser Beam Angle Measurement
Photonics 2023, 10(7), 704; https://doi.org/10.3390/photonics10070704 - 21 Jun 2023
Viewed by 713
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  
Article
Seven-Grooved-Rod, Side-Pumping Concept for Highly Efficient TEM00-Mode Solar Laser Emission through Fresnel Lenses
Photonics 2023, 10(6), 620; https://doi.org/10.3390/photonics10060620 - 26 May 2023
Viewed by 540
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  
Communication
Alexandrite and Nd:YAG Laser vs. IPL in the Management of Facial Hirsutism: A Retrospective Study
Photonics 2023, 10(5), 572; https://doi.org/10.3390/photonics10050572 - 14 May 2023
Viewed by 1714
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  
Article
Temperature Changes during Er:YAG Laser Activation with the Side-Firing Spiral Endo Tip in Root Canal Treatment
Photonics 2023, 10(5), 488; https://doi.org/10.3390/photonics10050488 - 24 Apr 2023
Viewed by 924
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  
Article
High Efficiency and High Stability for SHG in an Nd:YVO4 Laser with a KTP Intracavity and Q-Switching through Harmonic Modulation
Photonics 2023, 10(4), 454; https://doi.org/10.3390/photonics10040454 - 14 Apr 2023
Viewed by 1216
Abstract
In this paper, the stabilization and high efficiency of an unstable Second Harmonic Generation (SHG) of an Nd:YVO4 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 Nd:YVO4 laser with a KTP intracavity is demonstrated. By using a passive Q-switching crystal (Cr4+:YAG) and a parametric modulation method (harmonic modulation), the stabilization of the laser is reached. An harmonic modulation was applied to the pumping of the Nd:YVO4-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  
Article
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
Photonics 2023, 10(4), 439; https://doi.org/10.3390/photonics10040439 - 12 Apr 2023
Cited by 2 | Viewed by 937
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  
Communication
Coupling of Photonic and Plasmonic Modes for Double Nanowire Cavities
Photonics 2023, 10(4), 415; https://doi.org/10.3390/photonics10040415 - 06 Apr 2023
Viewed by 924
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  
Communication
Multi-Bessel Beams Generated by an Axicon and a Spatial Light Modulator for Drilling Applications
Photonics 2023, 10(4), 413; https://doi.org/10.3390/photonics10040413 - 06 Apr 2023
Cited by 2 | Viewed by 1219
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  
Article
CO2 and Diode Lasers vs. Conventional Surgery in the Disinclusion of Palatally Impacted Canines: A Randomized Controlled Trial
Photonics 2023, 10(3), 244; https://doi.org/10.3390/photonics10030244 - 23 Feb 2023
Viewed by 1298
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  
Communication
Simultaneous Manipulation of the Temporal and Spatial Behaviors of Nanosecond Laser Based on Hybrid Q-Switching
Photonics 2023, 10(2), 227; https://doi.org/10.3390/photonics10020227 - 20 Feb 2023
Viewed by 937
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  
Communication
Generalized Poincaré Beams in Tight Focus
Photonics 2023, 10(2), 218; https://doi.org/10.3390/photonics10020218 - 16 Feb 2023
Cited by 1 | Viewed by 856
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  
Article
A Tunable Optoelectronic Oscillator with Phase-to-Amplitude Modulation Transformation via an Acetylene Reference Cell
Photonics 2023, 10(2), 196; https://doi.org/10.3390/photonics10020196 - 12 Feb 2023
Viewed by 871
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  
Communication
Statistical Mixture of Kaleidoscope States Interacting with a Two-Level Atom: Entropy and Purification
Photonics 2023, 10(2), 150; https://doi.org/10.3390/photonics10020150 - 31 Jan 2023
Viewed by 945
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  
Article
Flexible, Stretchable, Tunable, and Switchable DFB Laser
Photonics 2023, 10(1), 12; https://doi.org/10.3390/photonics10010012 - 23 Dec 2022
Viewed by 1071
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  
Article
Implementation of Logic Gates in an Erbium-Doped Fiber Laser (EDFL): Numerical and Experimental Analysis
Photonics 2022, 9(12), 977; https://doi.org/10.3390/photonics9120977 - 12 Dec 2022
Cited by 2 | Viewed by 1152
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  
Review
Evolving Role of Lasers in Endourology: Past, Present and Future of Lasers
Photonics 2023, 10(6), 635; https://doi.org/10.3390/photonics10060635 - 31 May 2023
Viewed by 1173
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  
Systematic Review
Therapeutic and Adverse Effects of Lasers in Dentistry: A Systematic Review
Photonics 2023, 10(6), 650; https://doi.org/10.3390/photonics10060650 - 05 Jun 2023
Cited by 2 | Viewed by 1791
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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