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Dental lasers: principles and practice of safety
摘要： Lasers have great potential to improve treatment and are being increasingly used in dentistry. Patients, practice staff and visitors need to be protected from their potentially harmful effects on the skin and eyes, so dental staff need to understand and apply safety principles.
关键词： risk assessment,safety principles,Dental lasers,protective eyewear,skin and eye protection
更新于2025-09-23 15:21:01
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Multi-wavelength colloidal quantum dot lasers in distributed feedback cavities
摘要： Lasers with multi-wavelength colloidal quantum dots (CQDs) can be achieved using complex grating structures and ?exible substrate. The structure contains graduated periods and rectangular cavity fabricated through interference lithography, which acts as the distributed feedback cavity. A layer of densely packed CQD ?lm is deposited on the cavity via spin coating technique. The performance of CQD lasers based on di?erent distributed feedback cavities is investigated. Multi-wavelength lasing is achieved based on a ?exible rectangular cavity.
关键词： ?exible,tunable,distributed feedback,quantum dots lasers,multi-wavelength
更新于2025-09-23 15:21:01
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Volume Fabrication of Quantum Cascade Lasers on 200 mm-CMOS pilot line
摘要： The manufacturing cost of quantum cascade lasers is still a major bottleneck for the adoption of this technology for chemical sensing. The integration of Mid-Infrared sources on Si substrate based on CMOS technology paves the way for high-volume low-cost fabrication. Furthermore, the use of Si-based fabrication platform opens the way to the co-integration of QCL Mid-InfraRed sources with SiGe-based waveguides, enabling realization of optical sensors fully integrated on planar substrate. We report here the fabrication and the characterization of DFB-QCL sources using top metal grating approach working at 7.4 μm fully implemented on our 200 mm CMOS pilot line. These QCL featured threshold current density of 2.5 kA/cm2 and a linewidth of 0.16 cm?1 with a high fabrication yield. This approach paves the way toward a Mid-InfraRed spectrometer at the silicon chip level.
关键词： Mid-Infrared sources,DFB-QCL sources,Si substrate,CMOS technology,Quantum Cascade Lasers
更新于2025-09-23 15:21:01
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Enhanced 2???μm Mida??Infrared Laser Output from Tm <sup>3+</sup> a??Activated Glass Ceramic Microcavities
摘要： Transparent glass ceramics (GCs) consisting of an homogeneous glass phase and a well-dispersed crystal phase are considered as ideal optical gain materials potentially applied in optoelectronic devices due to the combination of facile processability of glass and the intense crystal ?eld of nanocrystals. Here, a heat-induced nanocrystal-in-glass method is employed to integrate the active ions Tm3+ into Bi2Te4O11 nanocrystals with an intense crystal ?eld to realize an enhanced microlaser output. This strategy endows the e?cient tellurate GC microcavity laser operating at ≈2 μm. Compared with the laser properties of as-prepared glass microcavities, the pump threshold (260 μW) is as low as less than a quarter and the slope e?ciency (0.0296%) is 5.5 times higher. Furthermore, by carefully engineering the heat treatment temperature and duration, the crystal size and distribution can be precisely controlled. Thus, the Rayleigh scattering loss that is detrimental to quality (Q) factor is e?ectively suppressed and the GC microcavities with high Q factors up to 105 are successfully obtained. This work provides useful insight on the development of optical functional materials and expands the practical applications of GC microcavities in various optoelectronic ?elds.
关键词： mid-infrared lasers,glass-ceramic microspheres,microcavities,whispering gallery mode
更新于2025-09-23 15:21:01
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Enhancing Perovskite Solar Cell Performance through Femtosecond Laser Polishing
摘要： Nonradiative recombination loss is a key process that determines the performance of perovskite solar cells, and how to control it is significant for the research and development of perovskites. Generally, traditional chemical modification/passivation methods are complicated and prone to secondary contamination. Here, we demonstrate femtosecond (fs) laser polishing as a promising technique to ameliorate the surface of perovskite films, to reduce nonradiative recombination loss and improve solar cell performance. The high-intensity fs laser pulses can remove around 20-nm thick perovskite top-layer through ionization process, help to decrease the grain boundary density and enlarge the grain size of perovskite films after recrystallization. We believe that fs laser polishing is a time-effective and highly precise technique which is suitable for large-scaled device production, thus will trigger more applications in optoelectronics.
关键词： femtosecond lasers,perovskites,recombination,passivation,solar cells
更新于2025-09-23 15:21:01
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Broadband Ultrashort Pulses in Passively Mode-Locked Fiber Lasers
摘要： Generation of ultrashort pulses with an ultimately broad spectrum in fiber lasers is investigated by using numerical modeling and analytical calculations. It is demonstrated that the spectral width of the generated pulses can be several times larger than the gain bandwidth of the laser active medium.
关键词： passive mode-locking,spectra of pulses,generation dynamics,fiber lasers
更新于2025-09-23 15:21:01
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Photoselective Vaporesection of the Prostate with an End-firing Lithium Triborate Crystal Laser
摘要： Background: Photoselective vaporization of the prostate is a technique that is widely used for the treatment of benign prostatic hyperplasia (BPH) and has pronounced advantages compared to the traditional transurethral resection of the prostate. Following the recent introduction of end-firing lithium triborate lasers, we have created a new technique called photoselective vaporesection of the prostate (PVRP). This study described our initial experience using the PVRP technique for the treatment of BPH. Methods: This prospective study included a total of 35 patients with BPH who underwent PVRP from August 2013 to July 2014. The chief clinical parameters were obtained and evaluated during the perioperative period and follow-up, including the International Prostate Symptom Score (IPSS), quality of life (QoL) score, maximum urinary flow rate, and prostate volume. All variables were evaluated for statistically significant differences compared to baseline values using the analysis of variance. Results: The mean subgroup IPSS and QoL scores significantly improved during follow-up; the respective decreases in IPSS storage score, IPSS voiding score, IPSS nocturia score, and QoL score were 75.3%, 83.6%, 51.4%, and 71.7%, respectively (all P < 0.001 compared with baseline). Three patients were diagnosed with prostate cancer based on postoperative pathological examinations. There were no serious perioperative complications. Conclusion: The PVRP technique demonstrates satisfactory short-term clinical outcomes and perioperative safety in the treatment of BPH.
关键词： Lasers,Treatment Outcome,Benign Prostatic Hyperplasia
更新于2025-09-23 15:21:01
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Investigation the effect of laser ablation parameters in a liquid in order to reduce the pulse energy during laser shock peening
摘要： The features of laser shock peening technology was studied in relation to the physical processes occurring during and after laser treatment. The effect of laser parameters on the results of the process was investigated. It was shown that the reduce of the diameter of the laser spot while maintaining the intensity leads to a decrease in the effect of LSP. This phenomenon was studied from the point of view of the features of plastic deformation at various sizes of the treatment zone using the standard model for the LSP process. Besides the features of the development of a plasma plume during laser ablation in a liquid are considered. It was shown that the liquid determines the geometry of the plume evolution and the shock wave caused by it. The process parameters used and the results obtained are important for the development of low-energy LSP technology.
关键词： Surface treatment,Laser shock peening,Laser-produced plasmas,Laser ablation in liquid,Nickel alloys,Laser pulses,Lasers
更新于2025-09-23 15:21:01
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Pumping Systems for Compton Free-Electron Lasers: Microwave Undulators and Powering Sources
摘要： The concept of Compton-type free-electron lasers (FELs) operating in short wavelength ranges with a high e?ciency and power level is currently underway at the IAP RAS (Nizhny Novgorod). This concept is aimed at reducing the energy of a driving relativistic electron beam and thereby increasing the e?ciency of the electron–wave interaction in FELs, as well as making the oscillator relatively compact. The basis of this concept is microwave undulators of a new type — the so-called “?ying” undulators. This paper is devoted to the results of the current studies of these undulators, their simulation, and “cold” electrodynamic tests in the Ka band. For powering microwave undulators, a spatially extended narrow-band ˇCerenkov surface-wave oscillators (SWOs) are developed in the speci?ed frequency range driven by Sinus-6, a high-current accelerator, with a particle energy of 0.5 MeV, a current of 5 kA, and a pulse duration of 25 ns. The required sub-gigawatt power level of output radiation combined with a high stability of the narrow-band oscillation regime is achieved under conditions of a strongly oversized oscillator by using two-dimensional distributed feedback provided in a 2D doubly-periodic slow-wave structure. The design parameters of a 32 GHz/0.5 GW SWO intended for powering microwave undulators are presented and the results of its simulation and reported.
关键词： flying undulators,Ka band,Cerenkov surface-wave oscillators,Sinus-6 accelerator,microwave undulators,Compton-type free-electron lasers
更新于2025-09-23 15:21:01
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Increasing the efficiency of material removal using dual laser micromachining
摘要： A continuous wave melting laser combined with a nanosecond ejection laser has been shown to improve the material removal efficiency by a factor of 2 to 8 compared with laser ablation processes reported in the literature. The decrease in the energy required for the combined lasers is primarily due to the optimisation of the irradiation time in the melting process, which is responsible for the majority of the total energy. For the laser used in this study, the optimal interaction time corresponding to the highest melting efficiency was found at 9-ms melting time, and this value is compared with results derived from a one-dimensional heating model. Metallurgical images of only melting and the produced hole after introducing the ejection pulse for the most efficient melting were presented as evidence of melt ejection. The results show that approximately 90% of the melt pool is ejected with little redeposited material at the periphery of the hole.
关键词： Beam-matter interaction,Short pulsed lasers,Laser material processing,Laser melting
更新于2025-09-23 15:21:01