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Measuring Algorithmic Complexity in Chaotic Lasers
摘要： Thanks to the simplicity and robustness of its calculation methods, algorithmic (or Kolmogorov) complexity appears as a useful tool to reveal chaotic dynamics when experimental time series are too short and noisy to apply Takens’ reconstruction theorem. We measure the complexity in chaotic regimes, with and without extreme events (sometimes called optical rogue waves), of three different all-solid-state lasers: Kerr lens mode locking femtosecond Ti:Sapphire (“fast” saturable absorber), Nd:YVO4 + Cr:YAG (“slow” saturable absorber) and Nd:YVO4 with modulated losses. We discuss how complexity characterizes the dynamics in an understandable way in all cases, and how it provides a correction factor of predictability given by Lyapunov exponents. This approach may be especially convenient to implement schemes of chaos control in real time.
关键词： self-pulsing lasers,randomness,Kolmogorov complexity
更新于2025-09-23 15:19:57
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Sub-200-kHz single soliton generation in a long ring Er-fiber laser with strict polarization control by using twisted fiber
摘要： In the present work we demonstrate a novel single-soliton ultra-low pulse repetition frequency passively mode-locked erbium-doped fiber laser. We mitigate the residual linear birefringence of fiber by fiber twist to achieve a strict control of polarization. For mode-locking the nonlinear polarization rotation (NPR) was used. Special technique was applied to reduce the overdriving of NPR that allows the generation of single soliton in ultra-long cavity. The strict control of polarization yields a stable relation between the polarization state of the pulses propagating in the cavity and the regimes of generation. A 192.12-kHz train of soliton pulses was obtained with pulse duration of 4.7 ps at 1560.1 nm, the average power was 29 μW and the estimated peak power was ? 30.8 W with an energy of 150.9 pJ.
关键词： Ultra-long laser cavity,Solitons,Nonlinear optics,Overdriving nonlinear effects,Mode-locked fiber lasers
更新于2025-09-23 15:19:57
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Outcome of a 980-nm diode laser coagulation in women with radiation-induced hemorrhagic cystitis: a single-center retrospective study
摘要： The purpose of this study was to evaluate the efficacy of a 980-nm diode laser coagulation in women with radiation-induced hemorrhagic cystitis (RHC). We conducted a retrospective study of 21 RHC patients treated with a 980-nm diode laser between July 2014 and December 2017 at our institution. Data was collected with regard to age, sex, lower urinary tract symptoms, use of transfusions, a drop in hemoglobin levels, indication of radiotherapy, median time between radiation therapy and presentation, previous treatments, operative time, mean energy used, number of coagulated areas, catheterization time, discharge time after treatment, hospital stay, and surgical outcome. All 21 patients were women with a median age of 52 years (range 36–68 years). Eighteen patients complained of frequency and urgency, four patients had dysuria, and one patient developed urinary retention. Radiation therapy was primarily indicated in the treatment of cervical cancer in 18 patients (85.7%) and endometrial cancer in three patients (14.3%). Nine patients (42.8%) received blood transfusion before surgery and three patients (14.3%) needed blood transfusion after the procedure. The mean decrease in hemoglobin prior to the procedure was 4.08 ± 2.04 g/dL. The median length of time from completion of radiotherapy to the presentation of hematuria was 38 months (range 8–65 months). All patients had failed an adequate trial of conservative treatment which included adequate hydration, hemostatics, continuous bladder irrigation (CBI), and clot evacuation at the bedside. Eleven patients (52.4%) had previously been treated with endoscopic electrocoagulation; the mean number of procedures was 1.73 ± 0.78 (range 1–3 sessions). Six patients (28.6%) underwent HBO, and sodium hyaluronate solution irrigation was administered to 3 patients (14.3%). The mean number of HBO sessions was 26.3 ± 16.8 (range 8–50), and the mean number of sodium hyaluronate solution irrigation procedures was 4.33 ± 1.53 (range 3–6). All operations were successful. The mean operative time was 45.6 ± 12.3 min, the mean number of coagulated areas was 11.7 ± 4.4, the mean energy used was 2.74 ± 1.14 kJ, the mean catheterization time was 6.2 ± 0.9 days, the mean discharge time after treatment was 6.8 ± 1.2 days, and the average length of a hospital stay was 7.4 ± 1.3 days. In 16 patients (76.2%), hematuria was completely resolved after one session of diode laser coagulation. Four patients (19.0%) underwent multiple sessions of laser treatment due to recurrent gross hematuria (three patients required two sessions and one patient required three sessions). Only one patient (4.8%) who had persistent gross hematuria after diode laser treatment (two sessions) underwent a radical cystectomy, which resolved the hematuria. The median hematuria-free interval of patients who had multiple procedures was 9 months (range 1–13 months). In total, 21 patients underwent 27 sessions of diode laser coagulation, and the median hematuria-free interval was 16 months (range 1–45 months) with a median follow-up of 25 months (range 7–48 months). Our study shows promising results for the management of patients with RHC; however, further evaluation with a larger cohort is required to confirm the efficacy of this treatment.
关键词： Diode lasers,Treatment outcome,Radiotherapy,Cystitis
更新于2025-09-23 15:19:57
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Bayesian Optimization of Terahertz Quantum Cascade Lasers
摘要： We use Bayesian optimization algorithms in combination with a nonequilibrium Green’s function transport model to increase the maximum operating temperature of terahertz quantum cascade lasers. This procedure lead to the recent temperature record of 210 K in terahertz quantum cascade lasers, and here we provide even-further-improved structures. The Bayesian optimization algorithm, which takes into account all the available history of the optimization, converges much faster and more securely than the commonly used genetic algorithm. Designs based on two and three wells per period are considered, and using the large amount of data generated, we systematically evaluate the studied schemes in terms of optimal extraction energy and relevance of electron-electron correlations. This analysis shows that the two-well scheme is superior for reaching high operating temperatures, while the three-well scheme is more robust to variations in layer thicknesses. Furthermore, we study the sensitivity to ?ux-rate ?uctuations during growth and simulation-model inaccuracies, showing the period thickness needs to be controlled to within a few percent, which is challenging but achievable with present-day molecular-beam epitaxy. These limits to the growth accuracy can be a guiding principle for experimentalists, along with the suggestion to fabricate devices across the wafer radius so as to ?nd the optimal period thickness.
关键词： Bayesian optimization,electron-electron correlations,nonequilibrium Green’s function,terahertz quantum cascade lasers,molecular-beam epitaxy
更新于2025-09-23 15:19:57
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Recent progress in laser materials processing and synthesis
摘要： Already today, high-power lasers have become indispensable for many areas of material processing such as welding, cutting, engraving or drilling. Without them, many industrial production processes are no longer possible. In the age of Industry 4.0, the integration of intelligent production systems and advanced information technologies, laser-assisted material processing, and synthesis will become even more important. Thanks to their high throughput, great precision, and efficiency as well as the excellent quality of the processed products laser-based technologies are on the way of becoming one of the most important processing and production routes of the future. By changing laser parameters such as wavelength or pulse durations many different types of materials, including metals, polymers, ceramics, and their composites can be processed. The energy required for processing can be provided in a localized volume with negligible heat transfer to the surrounding components. Due to these unique properties of lasers, new applications of the laser as a material processing tool are continuously made available. New process pathways in additive manufacturing, surface structuring, material deposition or nanoparticle synthesis are among the newer application areas of lasers.
关键词： nanoparticle synthesis,laser materials processing,laser synthesis,additive manufacturing,high-power lasers
更新于2025-09-23 15:19:57
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Minocycline-induced hyperpigmentation: rapid resolution after 755nm alexandrite picosecond laser treatment
摘要： Minocycline-induced pigmentation (MIP) is an infrequent complication of minocycline therapy, with four subtypes each with distinct clinical features and histologic staining patterns. MIP may resolve following discontinuation of minocycline therapy or it may persist indefinitely. A 64-year-old Caucasian male presented with a 6 month history of progressive blue-gray facial pigmentation distributed symmetrically over his face. One session utilizing a 755 nm picosecond Alexandrite laser resulted in immediate and significant clearance of the pigment in all treated areas. Long-term follow-up at 2 years revealed no recurrence of the MIP.
关键词： pigmentation,lasers,picosecond,Minocycline
更新于2025-09-23 15:19:57
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Fabrication of Tapered Circular Depressed-Cladding Waveguides in Nd:YAG Crystal by Femtosecond-Laser Direct Inscription
摘要： Crystalline materials are excellent substrates for the integration of compact photonic devices bene?ting from the unique optical properties of these materials. The technique of direct inscription with femtosecond lasers, as an advantage over other techniques, has opened the door to the fabrication of true three-dimensional (3D) photonic devices in almost any transparent substrate. Depressed-cladding waveguides have been demonstrated to be an excellent and versatile platform for the integration of 3D photonic circuits in crystals. Here, we present the technique that we have developed to inscribe tapered depressed-cladding waveguides with a circular section for the control of the modal behavior. As a proof of concept, we have applied the technique to fabricate structures in Nd:YAG crystal that e?ciently change the modal behavior from highly multimodal to monomodal, in the visible and near infrared, with reduction factors in the waveguide radius of up to 4:1. Our results are interesting for di?erent devices such as waveguide lasers, frequency converters or connectors between external devices with di?erent core sizes.
关键词： femtosecond lasers,crystalline dielectrics,photonic device,micro-processing,waveguide
更新于2025-09-23 15:19:57
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Generation of phase-locked beams by injection locking of extended-cavity diode lasers for atom interferometers
摘要： We report a novel method of generation of two phase-locked beams with a frequency offset at 6.834 GHz. The output of a master laser is modulated by an EOM and further injected into a slave laser that is an extended-cavity diode laser (ECDL). The ECDL amplifies laser power, and filters out unwanted modes (mostly the opposite sideband and the carrier mode) which could interfere Raman transitions and cause laser power fluctuations due to interference effect with the master laser. By injection locking, the slave laser to the first-order sideband of the modulated master laser beam, we achieve a phase noise below ? 50 dBc/Hz at the frequency range between 10 Hz and 100 kHz. The generated phase-locked beams are applicable to light pulse atom interferometers as the Raman lasers.
关键词： extended-cavity diode lasers,phase-locked beams,injection locking,atom interferometers
更新于2025-09-23 15:19:57
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Comment on a??Cooperative Behaviors in Amplified Emission from Single Microcrystals of Thiophene/Phenylene Coa??Oligomers toward Organic Polariton Lasera??
摘要： Yanagi et al. recently reviewed their progress in the field of amplified emission of thiophene/phenylene co-oligomers (TPCO) single crystals (Adv. Opt. Mater. 2019, 7, 1900136), which are a promising platform for highly efficient organic light-emitting devices. In this comment, the most intriguing experimental data from this paper are naturally and easily explained as an effect of unintentional impurities or molecular self-dopants that appear in the course of chemical synthesis of TPCO.
关键词： lasers,organic photoluminescence,thiophene/phenylene co-oligomers,molecular self-doping,organic optoelectronics
更新于2025-09-23 15:19:57
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A study on the heat distribution and oxidative modification of aged dammar films upon Er:YAG laser irradiation
摘要： This work shows the impact of one Er:YAG laser pulse to both the surface and bulk of aged dammar varnishes. Tests were performed in fluences ranging from 0.56 to 2.4J/cm2 and pulse durations of 100 and 300μs. Temperature changes upon irradiation were examined by (a) live recordings with an infrared thermal camera, and (b) determining the optical properties of the varnish, which allowed for estimates of the linear absorption coefficient and the temperature rise associated with the laser irradiation. Transmission and Fourier Transform Infrared (FTIR) spectroscopy studies captured increased energy transmissions through varnish films, as well as registering a reduction of hydroxides and carbon–hydrogen bonding as a function of fluence, respectively. FTIR and Differential Scanning Calorimetry (DSC) experimentally determined the absorption coefficient and the specific heat capacity of dammar films, and an overview of laser spots was carried out with Scanning Electron Microscopy (SEM). Evidence on the varnish response to Er:YAG laser irradiation is provided.
关键词： Er:YAG lasers,transmission,thermal effects,dammar varnish,analysis,modelling
更新于2025-09-23 15:19:57