Small-bore fluorocarbon polymer-coated silver hollow glass waveguides for Er:YAG laser light

Several types of fluorocarbon polymer (FCP)-coated silver hollow glass waveguides have been fabricated for Er:YAG laser delivery by using the improved wet chemical technique and dynamic coating procedure. The straight losses of 2 m long 700 μmØ and 540 μmØ waveguides are 0.4 and 1.0 dB, respectively. The transmission losses of these waveguides are below 1.5 dB even when the waveguides are bent to 180° with the bending radius of either 20 or 15 cm. The waveguides with the small diameters of 320 and 200 μm have also been developed for clinical treatment, which exhibit low enough transmission losses for Er:YAG laser light.     

Robust hollow devices and waveguides for Er:YAG laser radiation

Fluorocarbon-polymer (FCP) coated silver hollow stainless steel (St) devices and waveguides have been developed for Er:YAG laser radiation. Full liquid phase techniques have been adopted to coat the silver and FCP layers inside the stainless steel hollow structure. Both straight and bent robust hollow devices have been fabricated as the output optical elements for the delivery system of medical Er:YAG lasers. A robust hollow waveguide with the length of about 1.6 m has also been realized as an actual delivery system.     

Transmission of 1.6 J Er:YAG laser light by ZnS-coated silver hollow waveguides

A maximum energy of 1.6 J at 5 pps of Er:YAG laser light has been transmitted through a flexible ZnS-coated silver hollow waveguide which has an inner diameter of 800 μm and is 116 cm long. The straight waveguide loss is 0.6 dB m⁻¹ and no significant loss and mechanical changes have been found after an endurance test of 10000 pulse transmissions and bending 400 times with a bending radius of 30 cm.     

Influence of doping the pump-chamber material in a flashlamp pumped Er:YAG laser

The influence of the conversion of pump light of wavelengths below 400 nm into pump light with a central wavelength of 500 nm in a Europium doped quartzglass pump chamber has been investigated. The results are compared to the ones from an undoped quartzglass. The measurements resulted in a reduction of the slope efficiency by a factor of two for the doped quartzglass compared to the undoped one. Furthermore, the pump-pulse lengths around 80 μs lead to a decrease in the slope efficiency compared to pump-pulse lengths above 100 μs.     

Effect of Er:YAG laser energy on the morphology of enamel/adhesive system interface

The aim of this study was to evaluate in vitro the influence of Er:YAG laser energy variation to cavity preparation on the morphology of enamel/adhesive system interface, using SEM. Eighteen molars were used and the buccal surfaces were flattened without dentine exposure. The specimens were randomly assigned to two groups, according to the adhesive system (conventional total-etching or self-etching), and each group was divided into three subgroups (bur carbide in turbine of high rotation, Er:YAG laser 250 mJ/4 Hz and Er:YAG laser 300 mJ/4 Hz) containing six teeth each. The enamel/adhesive system interface was serially sectioned and prepared for SEM. The Er:YAG laser, in general, produced a more irregular adhesive interface than the control group. For Er:YAG laser 250 mJ there was formation of a more regular hybrid layer with good tag formation, mainly in the total-etching system. However, Er:YAG laser 300 mJ showed a more irregular interface with amorphous enamel and fused areas, for both adhesive systems. It was concluded that cavity preparation with Er:YAG laser influenced on the morphology of enamel/adhesive system interface and the tissual alterations were more evident when the energy was increased.     

303MHz高重复频率掺Er光纤飞秒激光器

高重复频率掺Er光纤飞秒激光器在光学频率梳、超高速光学采样等领域具有很重要的作用. 本文采用非线性偏振旋转锁模机理, 在掺Er光纤飞秒激光器中实现了重复频率为303 MHz的锁模脉冲输出. 通过优化腔内色散, 激光器腔内色散在零色散附近偏负值, 锁模后工作在展宽脉冲锁模状态. 在817 mW抽运功率下, 激光器在连续光状态下可以输出125 mW的平均功率, 在锁模状态下可以输出69 mW的平均功率, 脉冲宽度为90 fs. 当抽运功率处于700-817 mW时, 激光器可以实现自启动锁模. 激光器重复频率在5 h内的漂移量为30 Hz.     

Er^3＋：YAG晶体Er^3＋离子的浓度对电磁感应光透明的影响

在一个三能级模型中展示了Er^3 :YAG晶体中的Er^3 浓度对电磁感应光透明（EIT）的影响。没有耦合场时,Er^3 离子浓度在15％左右时吸收达到最大;存在共振耦合场时,Er^3 离子浓度在3％左右时透射有一个最优值。     

Er,Yb:YAG微晶玻璃发光特性的研究

高温熔制Er³⁺，Yb³⁺离子掺杂CaO-Y₂O₃-Al₂O₃-SiO₂系统玻璃，并进行微晶化处理，研究了微晶玻璃中Er³⁺离子的发光及上转换发光特性，分析了微晶玻璃上转换发光机理.结果表明：原始玻璃经热处理得到了Er,Yb:YAG微晶玻璃，微晶玻璃中Er³⁺离子在室温下⁴I_13/2→⁴I_15/2跃迁产生横盖1450—1650nm区间的超宽带荧光，荧光半高宽达180nm，这可能由于YAG微晶相中Er³⁺离子与玻璃相中残留Er³⁺离子的共同发光；Er³⁺与Yb³⁺离子局域基质声子能量的降低使微晶玻璃Er³⁺离子上转换发光强度与原始玻璃相比显著提高，绿光、红光上转换荧光强度比玻璃样品分别增强约7和3倍；微晶化后Er³⁺，Yb³⁺离子局域环境发生变化也导致微晶玻璃中Er³⁺离子绿光、红光上转换发光相对强度发生变化. 关键词： 铒 镱:钇铝石榴石 微晶玻璃 荧光光谱     

Experimental study of electro-optical Q-switched pulsed Nd:YAG laser

We report the specification of a compact and stable side diode-pumped Q-switched pulsed Nd:YAG laser. We experimentally study and compare the performance of the pulsed Nd:YAG laser in the free-running and Q-switched modes at different pulse repetition rates from 1 Hz to 100 Hz. The laser output energy is stabilized by using a special configuration of the optical resonator. In this laser, an unsymmetrical concave-concave resonator is used and this structure helps the mode volume to be nearly fixed when the pulse repetition rate is increased. According to the experimental results in the Q-switched operation, the laser output energy is nearly constant around 70 mJ with an FWHM pulse width of 7 ns at 100 Hz. The optical-to-optical conversion efficiency in the Q-switched regime is 17.5%.     

Potential of Nd:YAG pulsed laser deposition method for coated conductor production

A Nd:YAG laser is environmentally safe and economical with no poisonous or hazardous gases and no expensive gases. We prepared Y123 films by using the fourth harmonic Nd:YAG pulsed laser deposition (PLD) method and optimized the deposition conditions on MgO single crystalline substrates and IBAD-MgO substrates for Y123 coated conductor. We found that the optimal deposition conditions acquired bi-axially aligned Y123 films on both substrates with T_c ∼ 90 K and J_c > 1 MA/cm² at 77 K in self-field. For obtaining high I_c, we fabricated thick Y123 films on both substrates and the maximum I_c per 1 cm in width reached 186 A/cm-width on the IBAD-MgO substrate. Interestingly, there were no a-axis oriented grains within the films up to 1.8 μm thick. This might be an especial feature of the Nd:YAG-PLD method. We believe that the Nd:YAG-PLD method is promising method for RE123 coated conductor production.     

A parametric study of pulsed Nd:YAG laser micro-drilling of gamma-titanium aluminide

In the present research, Nd:YAG laser micro-drilling of gamma-titanium aluminide, a new material which has performed well in laboratory tests as well as in different fields of engineering, is studied. The effect of different process parameters in the optimization of the process is investigated. The aspects considered are the hole circularity at exit and the hole taper of the drilled hole. Lamp current, pulse frequency, air pressure and thickness of the job are selected as independent process variables. The central composite design (CCD) technique based on response surface methodology (RSM) is employed to plan the experiments to achieve optimum responses with a reduced number of experiments.     

Investigation of Cr:YAG passive mode-locking in a pulsed Nd:YAG laser

Passive mode-locking of a pulsed Nd:YAG laser using a Cr⁴⁺:YAG saturable absorber was realized for the first time in a nearly critical stable resonator containing an antiresonant ring structure. The output energy and pulse duration are 13.5 mJ and 180 ps, respectively. The recovery time and saturable intensity for excited-state absorption of Cr⁴⁺:YAG under the action of strong laser pulses were calculated from rate equations.     

高平均功率六棒串接脉冲Nd:YAG激光器

报道了一种腔内六棒串接的脉冲Nd:YAG激光器。采用44矩阵对晶体棒失调角度对谐振腔光轴的影响进行了理论分析,给出了六棒串接脉冲激光器中晶体棒失调角度的允许范围。在串接实验中,谐振腔采用对称平平腔结构,通过调整每根晶体棒的失调角度到允许范围内,实现了六棒串接脉冲Nd:YAG激光器。在输入电功率86 kW,占空比17%时,获得了平均功率3 018 W的脉冲激光输出,峰值功率17.75 kW,最高单脉冲能量为66 J,光束参数乘积为26.3 mmmrad,电光转换效率3.5%,长时间工作不稳定性小于2%。     

Tunable single-longitudinal-mode operation of a sandwich-type YAG/Ho:YAG/YAG ceramic laser

We present a 2.09 μm single-longitudinal-mode sandwich-type YAG/Ho:YAG/YAG ceramic laser pumped by a Tm-doped fiber laser for the first time. A pair of F-P etalons was used to achieve tunable single-longitudinal-mode operation. The maximum single-longitudinal-mode output power of 530 mW at 2091.4 nm was obtained with an absorbed pump power of 8.06 W, corresponding to an optical conversion efficiency of 6.6% and a slope efficiency of 12.7%. Wavelength tunable was achieved by tuning the angle of etalons and the wavelength could be tuned from 2091.1 nm to 2092.1 nm, corresponding to a tuning frequency of 68 GHz. The M² factor was measured to be 1.23.     

Raman and IR reflection micro‐spectroscopic study of Er:YAG laser treated permanent and deciduous human teeth

Permanent and deciduous human teeth treated by a dental Er‐doped yttrium‐aluminium‐garnet pulse laser (λ = 2940 nm) as well as by classical drilling tools under conditions typical of the clinical practice were studied by ultraviolet Raman and Fourier transform infrared (FTIR) reflection microspectroscopy. Enamel was analyzed by both spectroscopic methods, whereas dentine was studied only by FTIR reflection because of the high level of photoluminescence continuum background even when a wavelength of 325 nm was used in inelastic light scattering experiments. The applied energy and pulse frequency of the dental laser varied between 200 and 500 mJ and between 10 and 30 Hz, respectively. The most important result is that after the laser treatment, the hydroxyapatite structure in both permanent and deciduous enamel is preserved: the apatite Ca‐P‐O framework remains intact, and the content of channel OH^‐ groups is not changed within experimental uncertainties. The calcium‐phosphate framework of dentine also exhibits negligible laser‐induced changes. The only alterations in enamel induced by laser as well as by mechanical drilling are reduction of the amount of CO₃^2‐ in apatite and changes in the protein conformation. The laser impact on the organic material and carbonate groups is strongest for laser power of 8 W; for powers of 4 or 5 W, the combination of higher pulse energy and lower pulse frequency has less impact than the combination of lower energy and higher frequency. No differences between deciduous and permanent teeth in their resistivity to laser irradiation with λ = 2940 nm were detected. Copyright © 2013 John Wiley & Sons, Ltd.     

透明Nd:YAG激光陶瓷的研究与应用进展

综述了近年来,特别是近两年来国内外透明Nd:YAG激光陶瓷的研究与应用情况,重点对我国的透明Nd:YAG激光陶瓷研究近况进行了分析,指出了透明Nd:YAG激光陶瓷是目前陶瓷研究的热点。提出了透明Nd:YAG激光陶瓷研究中尚存在的问题和我国在此领域中与国外研究的巨大差距。分析指出:我国研究透明Nd:YAG激光陶瓷的各个院所之间,应该强强联合,优势互补,对该领域的理论和制备工艺进行更为深入的研究。     

Spectroscopic characterization of low-nickel copper welding with pulsed Nd:YAG laser

Effects of various operating parameters of 400 W pulsed Nd:YAG laser on welding of nickel-alloyed copper have been investigated. The induced plume spectra in case of using different assist gases and preheat temperatures have been analyzed and the effects of these key factors on melt features such as penetration depth, porosity and spattering have been attributed to the spectroscopic behavior of the plume. Moreover, the CuI electron temperature and its standard deviation as the spectroscopic responses of the plasma plume to various laser process parameters have been quantitatively evaluated at different average and peak powers and pulse energies. Also, the mentioned responses were utilized to justify the weld bead profile features, involving weld depth, width and their stabilities, at similar process parameters. The operating conditions of welding were optimized, regarding the results of spectroscopic observations and attributing them to the qualitative aspects of the melt pool.     

脉冲Nd:YAG激光熔覆修复塑料模具工艺参数的优化

 激光器的电压、电流、脉冲宽度、脉冲频率与激光的扫描速度、光斑直径等工艺参数直接影响着脉冲Nd:YAG激光熔覆质量。为了简化工艺调整过程，提出了重叠率的概念，并进行了理论推导，建立了重叠率与脉冲频率、激光扫描速度、激光光斑直径相互关系的方程式。利用预置法在低碳钢基体上熔覆Ni基合金粉末,获得了2组最佳工艺参数，即单脉冲能量、重叠率分别为6.7 J,97.4%和21 J,69.4%。研究表明：在单脉冲能量和重叠率一定的条件下，改变电流、脉宽、脉冲频率及熔覆速度不会影响熔覆质量。     

脉冲Nd:YAG激光烧蚀Cu产生等离子体总辐射的时空分辨研究

通过时空分辨的光谱测量技术,测定了在环境气压下,Ｎｄ：ＹＡＧ脉冲激光烧蚀金属Ｃｕ产生等离子体的总辐射随时间与空间的强度分布,研究了烧蚀环境气压对总辐射强度的影响,提出了电子碰撞与复合激发模型。     

Formation of nano-crystalline and amorphous phases on the surface of stainless steel by Nd:YAG pulsed laser irradiation

Thin surface layers consisting of nano-crystalline and amorphous phases on the surface of stainless steel have been attained under the Nd:YAG pulsed laser irradiation. The phases and microstructures were investigated by X-ray diffraction (XRD) and high resolution transmission electron microscope (HRTEM). The phase compositions of the surface determined by XRD were α-Fe (ferrite) and γ-Fe (austenite) or only γ-Fe in the near surface region on the bases of the different laser power densities. The nano-crystalline grains with sizes of 4-100 nm could result from high cooling rate and crystallization in amorphous region by homogeneous and heterogeneous nucleation. The formation of the amorphous phase was attributed to the higher cooling rates.