- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Dynamics of Yb2+ to Yb3+ ion valence transformations in Yb:YAG ceramics used for high-power lasers
摘要： Due to the good thermal-mechanical and luminescence properties, Yb:YAG ceramics are suitable as thin-disk lasers; however, their efficiency is limited by the presence of Yb2t ions, which entail parasitic energy transfer from Yb3t formation in Yb:YAG ceramics prepared by solid-state reaction sintering. The samples were prepared by air annealing, the oxidation of the material leads to recharging Yb2t ion to its trivalent state. The activation energy was determined by Jander to be Ea(D) ? 2.7 ? 0.2 eV, which is in good agreement with the activation energy for oxygen diffusion in the YAG lattice. It was concluded that the recharging of Yb2t ion to its trivalent state in YAG ceramics is limited by the oxygen self-diffusion through the grain volume, and the oxygen vacancy alone and/or together with the presence of antisites can be proposed as Yb2t charge compensation mechanism in the YAG ceramics, unlike the YbAG single crystals, where tetravalent impurities are responsible for charge compensation.
关键词： Yb:YAG,Optical ceramics,Oxidation kinetics
更新于2025-09-19 17:13:59
-
[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - CPA-Free High Repetition Rate Few-Cycle OPCPA
摘要： Optical Parametric Chirped-Pulse Amplification (OPCPA) systems have become a key-enabling light source providing high energies at high repetition rates and covering a wide range of wavelengths from the visible to the mid-infrared with few cycle pulse durations. However, most systems are complex and rather bulky due to large fiber or regenerative amplifiers used as a pump source. The additional need for a stretcher and compressor in the pump laser adds complexity, timing jitter and reduces the overall optical-to-optical efficiency. In this work, we present a novel approach that allows a high repetition rate, few-cycle OPCPA system based on a compact and CPA-free solid-state amplifier system. We recently demonstrated the feasibility of the concept using two subsequent direct diode pumped solid-state amplifier modules (neoVAN-2P, neoLASE GmbH) based on Nd:YVO4 as a pump laser. We were able to amplify the ultrabroadband pulses from a home-built, octave-spanning Ti:sapphire laser to generate few-cycle pulses with a duration of 8.7 fs with an energy of 18 μJ at 10 kHz repetition rate. The compact, CPA-free system has a reduced system footprint and high efficiency as no losses in a compressor are occurring. For the amplification of few-cycle signal pulses, stretching to more than a few ps and subsequent recompression is problematic and limited the achievable pulse duration in our previous system. Insufficient temporal overlap between pump and signal pulses in the OPA stages will however cause lower parametric conversion efficiency and a significantly higher super-fluorescence background. In this work, we show for the first time a compact few-cycle OPCPA system using a newly developed Yb:YAG solid-state amplifier as pump source. The Yb:YAG amplifier modules are capable of generating pump pulses with a duration of < 600 fs. These output parameters are ideally suited for few-cycle OPCPA pumping and eliminate the above mentioned drawbacks of the previous approach. The high pump power and short pulse duration delivered by the amplifier modules enable a similar performance of the OPCPA as typical high repetition rate, rod-fiber based systems at the benefit of CPA-free operation and compactness. As the amplifier modules are equipped with an efficient CPA-free, directly diode pumped solid-state pump source with all-optical synchronization to an ultra-broadband Ti:sapphire seed oscillator. The availability of such portable, breadboard-user-friendly OPCPA will be a great benefit for many applications as spectroscopy, nonlinear imaging or even attosecond physics.
关键词： Yb:YAG,solid-state amplifier,few-cycle pulses,high repetition rate,OPCPA
更新于2025-09-19 17:13:59
-
Retrieval of Glass Fiber Post using Er:YAG Laser and Conventional Endodontic Ultrasonic Method: An In Vitro Study
摘要： Purpose: To compare the times and temperatures used to remove a glass fiber post from an endodontically-treated tooth using erbium-doped yttrium aluminum garnet (Er:YAG) compared to conventional endodontic ultrasonic method. Materials and Methods: Thirty four single-root human extracted teeth were endodontically treated ex vivo. The post space was prepared to 7 mm in depth and a 11.4 mm glass fiber post was cemented using composite resin cement. Specimens were kept in 100% humidity for 24 hours and then randomly assigned to Er:YAG laser or ultrasonic methods for post removal. The removal time was recorded. Specimens with a fractured post during the removal process were excluded. The temperature on the external surface of the root was measured at the coronal, middle, and apical third portions during the laser or ultrasonic applications from 1 to 10 minutes. Data were analyzed using one-tailed t-test and paired t-test (ɑ = 0.01) for the post removal time and temperature difference, respectively. The specimen surfaces were examined using scanning electron microscopy (SEM). Results: Fifteen specimens were tested in each group. Four specimens were fractured, 2 in the laser and 1 in ultrasonic group. One post was excluded because of laser tip damage. The average removal time were 98±46.1 seconds for Er:YAG laser and 538±215.6 seconds or ultrasonic groups with significant difference between the groups (p < 0.001). The temperature (°C) ranges measured from 1 to 10 minutes were [24.2°,27.3°] for laser and [33.0°, 38.0°] for ultrasonic in the cervical area, [22.1°,24.6°] for laser and [31.0°,34.6°] for ultrasonic in the middle area, and [24.4°,27.7°] for laser and [30.3°,34.1°] for ultrasonic in the apical area. There were significant differences between temperatures for each treatment (p < 0.001). SEM examination showed no visible damage caused by treatment with Er:YAG laser. Conclusions: Er:YAG laser can remove posts up to 5 times faster than ultrasonic removal method. The laser causes lower temperature increase at the root surface compared to the ultrasonic removal. Er:YAG may be considered as a viable alternative to sonication for post removal.
关键词： laser,Er:YAG,post and core,removal,ultrasonic
更新于2025-09-19 17:13:59
-
A Randomized, Splita??Face, Doublea??Blind Comparison Trial Between Fractionated Frequencya??Doubled 1064/532a??nm Picosecond Nd:YAG Laser and Fractionated 1927a??nm Thulium Fiber Laser for Facial Photorejuvenation
摘要： Fractionated lasers are a popular therapeutic option for facial photorejuvenation. In this study, we compare the safety, tolerability, and efficacy of a fractionated frequency‐doubled 1064/532 nm picosecond Nd:YAG fractionated picosecond laser (FPL) versus a fractionated 1927 nm thulium fiber laser (TFL) for facial rejuvenation. This was a double‐blind, randomized, split‐face comparison study involving 20 subjects. Facial halves were randomized to receive either FPL or TFL treatment. Three treatments were delivered at 1‐month intervals. Subjects were followed up for 1, 3, and 6 months post‐final treatment session and evaluated by blinded, non‐treating investigators for dyspigmentation, erythema, keratosis, texture, and rhytids on a standardized scale. Subjects also recorded a quantitative daily diary rating healing progress for 14 days after every treatment session. Statistically significant improvements in elastosis, erythema, keratosis, dyschromia, and skin texture were noted in both treatment groups. There were no significant differences detected in clinical efficacy between the two groups. Subject daily diaries revealed statistically significant differences in tolerability during the immediate 14‐day post‐operative recovery period. The facial half treated with FPL displayed significantly less redness on days 3 and 4; significantly less swelling on day 5; significantly less crusting on days 1 through 9; significantly less peeling on days 3 through 9; and significantly less itch on days 4 and 7. There were no unexpected adverse effects observed. Both FPL and TFL are safe and effective treatment options for facial rejuvenation. FPL may be associated with significantly less downtime.
关键词： photodamage,laser induced optical breakdown,photothermolysis,thulium fiber,picosecond laser,photoacoustolysis,Nd:YAG,holographic lens,clinical trial,rejuvenation
更新于2025-09-19 17:13:59
-
The Effect of Capsulotomy Shape on Intraocular Light-Scattering after Nd:YAG Laser Capsulotomy
摘要： Purpose. To investigate the effects of capsulotomy shape on the visual acuity and visual quality after neodymium: yttrium aluminum garnet laser capsulotomy. Methods. In this study, a total of 42 eyes from 35 patients with posterior capsule opacification were divided into the circular and cruciate groups. The corrected distance visual acuity (CDVA), objective scatter index (OSI), modulation transfer function cutoff (MTF cutoff), Strehl ratio, and Optical Quality Analysis System values at contrasts of 100%, 20%, and 9% (OV-100, OV-20, and OV-9) were measured at precapsulotomy and 1 week and 1 month postcapsulotomy. The pseudophakic dysphotopsia questionnaire (PDQ) was used to evaluate the subjects’ satisfaction with treatment. Results. OSI values were significantly higher in the cruciate group than in the circular group at 1 week and 1 month after capsulotomy (P = 0.013 and P < 0.001). No significant difference was found in the OSI values between the two groups before capsulotomy (t = 0.52; P = 0.61). The decrease in OSI was higher in the circular group than in the cruciate group at 1 week and 1 month after capsulotomy (P = 0.036 and P = 0.019). No significant differences were found in the Strehl ratio, MTF cutoff, CDVA, OV-100, OV-20, and OV-9 between the two groups at 1 week and 1 month after capsulotomy (P > 0.05). The PDQ results showed that patients with circular-shaped capsulotomy complained less with intolerance of bright lights than those with cruciate-shaped capsulotomy. Conclusions. Circular-shaped capsulotomy can induce less intraocular light scattering and increase patient satisfaction.
关键词： visual acuity,Nd:YAG laser capsulotomy,visual quality,intraocular light-scattering,capsulotomy shape
更新于2025-09-19 17:13:59
-
Different Numbers of Long-Pulse 1064-nm Nd-YAG Laser Treatments for Onychomycosis: A Pilot Study
摘要： Purpose. To examine the benefits of different numbers of 1064-nm Nd-YAG laser treatments in patients with onychomycosis. Methods. This was a pilot study of patients with onychomycosis who were divided into three groups: four treatment sessions (group A), eight sessions (group B), and 12 sessions (group C). Only infected nails of degrees II–III (Scoring Clinical Index for Onychomycosis) were included. Treatment was given once a week using a long-pulse Nd-YAG 1064-nm laser. Patients were followed at 8, 16, and 24 weeks after the first treatment. Side effects were recorded. Results. Treatments were completed for 442 nails in 102 patients. The efficacy rates at 8, 16, and 24 weeks were 35.5%, 38.7%, and 37.4% for group A; 31.4%, 41.7%, and 44.0% for group B; and 27.7%, 50.0%, and 55.4% for group C, respectively. There was a significant difference in the efficacy rate at 24 weeks (?? = 0.016) between groups A and C, but not for groups A vs. B, or for groups B vs. C. No difference in the efficacy rate at 8 or 16 weeks was observed among the three groups. In all three groups, the efficacy was better for degree II nails than for degree III nails (all ?? < 0.05). No side effects occurred. Conclusions. The 1064-nm Nd-YAG laser had clinical benefits against onychomycosis. Higher numbers of treatments provided better long-term (24-week) benefits, but had no impact on the short-term outcomes. The efficacy of laser treatment on degree II onychomycosis was better than for degree III.
关键词： side effects,1064-nm Nd-YAG laser,treatment sessions,efficacy,onychomycosis
更新于2025-09-19 17:13:59
-
Bulk polycrystalline ceriaa??doped Al <sub/>2</sub> O <sub/>3</sub> and YAG ceramics for high-power density laser-driven solid-state white lighting: Effects of crystallinity and extreme temperatures
摘要： Here, we develop and characterize high thermal conductivity/high thermal shock-resistant bulk Ce-doped Al2O3 and propose it as a new phosphor converting capping layer for high-powered/high-brightness solid-state white lighting (SSWL). The bulk, dense Ce:Al2O3 ceramics have a 0.5 at.% Ce:Al concentration (significantly higher than the equilibrium solubility limit) and were produced using a simultaneous solid-state reactive current activated pressure-assisted densification (CAPAD) approach. Ce:Al2O3 exhibits a broadband emission from 400 to 600 nm, which encompasses the entire blue and green portions of the visible spectrum when pumped with ultraviolet (UV) light that is now commercially available in UV light–emitting devices and laser diodes (LD). These broadband phosphors can be used in the commonly used scheme of mixing with other UV-converting capping layers that emit red light to produce white light. Alternatively, they can be used in a novel composite down-converter approach that ensures improved thermal–mechanical properties of the converting phosphor capping layer. In this configuration, Ce:Al2O3 is used with proven phosphor conversion materials such as Ce:YAG as an active encapsulant or as a capping layer to produce SSWL with an improved bandwidth in the blue portion of the visible spectrum. To study the effect of crystallinity on the Ce photoluminescent (PL) emission, we synthesize Ce:YAG ceramics using high-pressure CAPAD at moderate temperatures to obtain varying crystallinity (amorphous through fully crystalline). We investigate the PL characteristics of Ce:Al2O3 and Ce:YAG from 295 to 4 K, revealing unique crystal field effects from the matrix on the Ce dopants. The unique PL properties in conjunction with the superior thermal–mechanical properties of Ce:Al2O3 can be used in high-powered/high-brightness–integrated devices based on high-efficiency UV-LD that do not suffer efficiency droop at high drive currents to pump the solid-state capping phosphors.
关键词： thermal conductivity,photoluminescent emission,high-power density,Ce-doped Al2O3,thermal shock-resistant,crystal field effects,solid-state white lighting,laser-driven,Ce:YAG
更新于2025-09-19 17:13:59
-
Laser Welding of Transmitting High-Performance Engineering Thermoplastics
摘要： Laser processing is a rapidly growing key technology driven by several advantages such as cost and performance. Laser welding presents numerous advantages in comparison with other welding technologies, providing high reliability and cost-effective solutions. Significant interest in this technology, combined with the increasing demand for high-strength lightweight structures has led to an increasing interest in joining high-performance engineering thermoplastics by employing laser technologies. Laser transmission welding is the base method usually employed to successfully join two polymers, a transmitting one through which the laser penetrates, and another one responsible for absorbing the laser radiation, resulting in heat and melting of the two components. In this work, the weldability of solely transmitting high-performance engineering thermoplastic is analyzed. ERTALON 6 SA, in its white version, is welded by a pulsed Nd:YAG laser. Tensile tests were performed in order to evaluate the quality of each joint by assessing its strength. A numerical model of the joint is also developed to support the theoretical approaches employed to justify the experimental observations.
关键词： pulsed Nd:YAG laser welding,numerical model,polyamide 6,ERTALON 6 SA,high-performance engineering thermoplastic,mechanical testing
更新于2025-09-19 17:13:59
-
Recorded color rendering index in single Ce,(Pr,Mn):YAG transparent ceramics for high-power white LEDs/LDs
摘要： Transparent ceramic (TC) is an incredibly promising color converter for high-power white LEDs/LDs. However, the preparation process of multiple structured TC with high color rendering index (CRI) is complicated and of technical challenge, and the inability of a single structured TC to achieve a high CRI significantly limits its real application. In this study, high quality single structured Ce,(Pr,Mn):YAG TCs with the 'wide peak' and 'narrow peak' red light emission were designed and fabricated by the solid-state reaction and vacuum sintering method. Compared with the emission spectra of the Ce:YAG TC, synchronous doping Pr3+ and Mn2+ ions into Ce:YAG TCs resulted in an inhomogeneous broaden of the full width at half maximum (FWHM) from 91.7 nm to 102.2 nm. Impressively, the CRI of the single Ce,(Pr,Mn):YAG TC based high-power white LEDs was as high as 84.8, and the correlated-color temperature (CCT) of the white LEDs/LDs were 5450 K and 3550 K, respectively. Furthermore, when the addition amounts of Pr3+ and Mn2+ were 0.2 at.% and 0.8 at.%, respectively, the prepared Ce,(Pr,Mn):YAG TC displayed a high quantum efficiency (IQE=48.14%) and an excellent color stability (only 5% fluctuation). Therefore, this work not only shows how to overcome the spectrum deficiencies of single structured TCs that restrains the intrinsic CRI improvement, but also provides a reference for the pursuit of a high luminescent property. It significantly reinforces the understanding of CRI problems of TC based high-power lighting, which is crucial for the real application of white LEDs/LDs.
关键词： color rendering index,Ce,(Pr,Mn):YAG,synchronous doping,high-power white LEDs/LDs,Transparent ceramic
更新于2025-09-19 17:13:59
-
Endoscopic Diagnosis and Treatment in Prostate Pathology || Laser Treatment for Benign Prostatic Hyperplasia
摘要： The word “LASER” is an acronym for “light amplification by stimulated emission of radiation.” Laser is one of the most important scientific discoveries of the last half of the twentieth century, often compared in importance with the discovery of electricity. Shortly after it was discovered, its applications in industry and especially in medicine increased continuously, contributing to many modern methods of diagnosis and treatment. The progress recorded over the last few years (the emergence of new types of lasers and optical fibers) has transformed laser into one of the ideal sources of energy used in medicine. The development of endoscopic instruments and the possibility of using laser fibers with very small diameters have significantly and positively influenced its use in urology, more than in any other medical specialty.
关键词： Er:YAG,Laser,Diode,Nd:YAG,Urology,Benign Prostatic Hyperplasia,Thulium,Ho:YAG,KTP
更新于2025-09-16 10:30:52