Selected area laser-crystallized polycrystalline silicon thin films by a pulsed Nd:YAG laser with 355 nm wavelength

Selected area laser-crystallized polycrystalline silicon(p-Si) thin films were prepared by the third harmonics (355 nm wavelength) generated by a solid-state pulsed Nd:YAG laser.Surface morphologies of 400 nm thick films after laser irradiation were analyzed.Raman spectra show that film crystallinity is improved with increase of laser energy.The optimum laser energy density is sensitive to the film thickness.The laser energy density for efficiently crystallizing amorphous silicon films is between 440-634 mJ/cm2 for 300 nm thick films and between 777-993 mJ/cm~2 for 400 nm thick films.The optimized laser energy density is 634,975 and 1571 mJ/cm~2 for 300,400 and 500 nm thick films,respectively.     

Study on the composite Nd：YAG crystal by laser micro- Raman spectroscopy

The composite Nd:YAG crystal with undoped YAG end caps was fabricated by thermal bonding technique. Scanning electron microscopy (SEM) result shows that the width of the bonded interface was about 0.5 μm. The laser micro-Raman was used to study the bonded interface of the composite crystal. The results of Raman spectra and the bonded interface image indicate that the undoped YAG and Nd:YAG crystals have been well bonded together. Furthermore, it can be drawn that the structure and the composition of the bonded interface are the same as the undoped YAG crystal, and that the Nd3 ions do not enter the bonded interface and the YAG side. This property is advantageous to decrease the thermal effect of the boned interface and to improve the laser stability.     

Conduction cooled narrow linewidth sub-nanosecond multi-beam laser

A conduction cooled high peak power, narrow linewidth, and sub-nanosecond multi-beam laser as an excellent candidate for non-scanning lidar is demonstrated. This laser is based on master oscillator power amplifier (MOPA) scheme which consists of a pulse pumped Nd:YAG/Cr4+:YAG microchip laser as the master oscillator and a high efficient grazing incidence Nd:YVO4 slab amplifier, and the output beam is expanded to 100 mm diameter by a 50× low aberration Galileo beam expander and then divided into a 50×2 staggered arrangement multi-beam array by a diffractive laser splitter. The laser operates at 1 064.28 nm with a spectral linewidth about 20 pm, which generates 1 mJ, 0.78 ns pulses at 7 kHz rate. The fluctuation of output power is less than ±2% when it works continuously for 1 h. The energy uniformity of the 100 sub-beams is up to 90%, the divergence of each sub-beam is about 20 μrad, and the total transmission efficiency of the diffractive laser splitter is more than 85%.     

Application of Various Lasers to Laser Trimming Resistance System

Though the laser trimming resistance has been an old laser machining industry for over 30 years, the development of technology brings new alternative lasers which can be used for the traditional machining. The paper describes application of various lasers to laser trimming resistance system including early traditional krypton arc lamp pumped Nd：YAG to laser, modern popular diode pumped solid state laser and the present advanced harmonic diode pumped solid state laser. Using the new alternative lasers in the laser trimming resistance system can dramatically improve the yields and equipment performance.     

Fabrication of narrow pulse passively Q-switched self- stimulated Raman laser with c-cut Nd:GdVO4

Combining the self-stimulated Raman scattering technology and saturable absorber of Cr4+:YAG, a 1.17 μm c-cut Nd:GdVO4 picosecond Q-switched laser is demonstrated in this paper. With an incident pump power of 10 W, the Q-switched laser with average power of 430 mW for 1.17 μm, pulse width of 270 ps, repetition rate of 13 kHz and the first order Stokes conversion efficiency of 4.3% is obtained. The Q-switched pulse width can be the narrowest in our research. In addition, the yellow laser at 0.58 μm is also achieved by using the LiB3O5 frequency doubling crystal.     

LD side-pumped intracavity frequency-doubled high Nd：YAG green laser based on acousto-optic Q-switch

A highly efficient and high power green laser generated by intracavity frequency doubling of a diode-sidepumped Q-switched Nd：YAG laser has been demonstrated. In the simple L-shaped cavity geometry,the maximum green output power of 28.5 W was obtained with a pulse width of 95 ns at a pulse repetition rate of 10 kHz by using a LBO crystal for frequency doubling,corresponding to a conversion efficiency of 11% from diode pump power to pulse green power. At a pulse repetition rate of 1 kHz,6.9 mJ of pulse energy,25 ns of pulse duration and 276 kW of peak power were obtained.     

KLu(WO4)2crystal as the Raman medium in a diode-pumped passively Q-switched Nd:YAG laser

A diode-pumped passively Q-switched Nd:YAG/KLu(WO 4 ) 2 (KLW) Raman laser is presented for the first time. As high as 1.89 W average output power is obtained at the pump power of 15.7 W with the pulse repetition frequency (PRF) of 27.2 kHz, and the corresponding diode-to-Stokes conversion efficiency is 12.0%. The highest pulse energy of 84.0 μJ is obtained. The obtained average output power and pulse energy are much higher than the previously reported results of diode-pumped passively Q-switched Raman lasers.     

Diode-pumped double passively Q-switched Nd：GdVO4 laser

Through using both Cr4 :YAG and GaAs saturable absorbers,a diode-pumped double passively Q-switched Nd:GdVO4 laser is realized and compared with a single passively Q-switched laser. This laser can generate symmetric pulse temporal profiles and shorter pulses. A laser pulse width of 17 ns has been achieved with the incident pump power of 8.5 W.     

A unified model in the pulsed laser ablation process

In this unified model,we introduce the electron-phonon coupling time(tie) and laser pulse width(tp).For long pulses,it can substitute for the traditional thermal conduction model;while for ultrashort pulses,it can substitute for the standard two-temperature model.As an example of the gold target,we get the dependence of the electron and ion temperature evolvement on the time and position by solving the thermal conduction equation using the finite-difference time-domain(FDTD) method.It is in good agreement with experimental data.We obtain the critical temperature of the onset of ablation using the Saha equation and then obtain the theoretical value of the laser ablation threshold when the laser pulse width ranges from nano-second to femtosecond timescale,which consists well with the experimental data.     

Ti:sapphire Laser Pumped Yb:YAG Laser with Cr4+:YAG as a Passive Q-switch

The Ti: sapphire laser pumped Yb: YAG passively- Q- switched laser with Cr4 +: YAG as a saturable absorber experiment was performed. The Mira 900 tunable Ti:sapphire laser with an output power up to 1 W was used as a pump source. The optical pump system was composed of a spherical lens (f = 75 mm) for focusing the pump beam to a circular spot with a diameter of about 50μm, the pumping power was measured to be up to 920 mW. The laser cavity was configured to be semispherical, and was formed by the 50 mm curvature radius mirror Mi and the flat mirror M2. Mirror Mt, one face was coated for high transmission at 940 nm and the other face was coated for total reflection at 940 nm and 1.03 μm, was placed on the front of the input facet of the Yb: YAG crystal. The Yb: YAG gain medium is doped with 20 at. - ％ Yb3+, no concentration quenching of the upper-state lifetime has been observed in this crystal. The Yb: YAG gain element is 8 × 8 × 0.5 mm3 thick and is polished flat and paralld. It is coated on one face of the crystal for high transmission at 940 nm and at 1030 nm, the other surface of the crystal is coated for total reflection at 940 nm and at 1030 nm. Mirror M2 was coated for total reflection at 940 nm and reflectivity of 97％ at 1.03 μm acting as an output coupler. The overal cavity length is 23 cm. More than 90％ of the laser pumping power was absorbed by the Yb: YAG crystal. The laser operation was performed at 278 K by using the constant-temperature water-cooled circulation with a copper surface. The Cr4+: YAG saturable absorber was placed tightly dose to Yb: YAG sample. This provided a train of pulsesat 1.03 μm with a pulse duration (FWHM) decreasing from 0.6 μs to 0.4 μs and a repetition rate increasing from 20 kHz to 50 kHz. The maximum average power of 53 mW is attained when the pmping power is 730 mW. The slope efficiency is about 16％.     

绝经后阴道流血的宫腔镜诊断与激光治疗

探讨宫腔镜对绝经后阴道流血的病因诊断和激光治疗的安全性和有效性。方法:对139例绝经后阴道流血患者作宫腔镜检查,根据镜下诊断结果分别行诊断性刮宫和宫腔镜直视下Nd:YAG激光治疗。结果:以病理标准为金标准,则宫腔镜诊断子宫内膜癌及子宫肉瘤的敏感性为100％,特异性为100％。诊断子宫内膜息肉的敏感性为97.1％,特异性为100％。诊断粘膜下肌瘤的敏感性为100％,特异性为100％。诊断萎缩性子宫内膜炎的敏感性为100％,特异性为100％。宫腔镜诊断与病理学诊断具有高度的一致性。所有手术均顺利进行,平均手术时间3.0±10.2分钟(3～30分钟),患者对宫腔镜检查的耐受性较好,术中术后未发生严重并发症,术后B超随访1～3月宫腔内赘生物均消失。结论:宫腔镜检查对绝经后阴道流血的病因具有较高的诊断价值,宫腔镜下激光治疗宫腔内良性病变如子宫内膜息肉和子宫粘膜下肌瘤安全可行。     

实验性犬气道肉芽肿及YAG：Nd激光治疗机理的研究

随着内窥镜检查及胸部手术的广泛开展、气管切开后金属插管的较长期使用,气管支气管肉芽肿以及良恶性肿瘤等已为常见疾病。激光治疗气管、支气管疾病在临床上已证明有效,但激光对气道粘膜的作用究竟如何尚鲜见报道。本实验应用机械刺激原理,置异物于大道某一部位,造成持续性刺激而促使该部位生长出炎性肉芽肿,然后以YAG:Nd激光照射汽化之,观察治疗后局部大体及镜下病理变化,旨在为临床激光治疗气道内阻塞性病变提供理论参考。     

KTP倍频Nd:YAG激光和Ho:YAG激光心肌打孔组织学变化的对比研究

目的 :比较国产 KTP倍频 Nd:YAG激光和 Ho:YAG激光对离体猪心激光打孔的组织学效应 ,探讨国产 KTP倍频 Nd:YAG激光用于激光心肌血运重建术的可能性。方法 :分别用 KTP倍频 Nd:YAG激光和 Ho:YAG激光以多种级别的工作参数对离体猪心左心室心内膜面进行照射 ,行病理组织学检查 ,测量激光孔道直径、深度及坏死层厚度。结果 :KTP倍频 Nd:YAG激光和 Ho:YAG激光均能有效形成激光孔道 ,随能量增加 ,孔道深度增加。KTP倍频 Nd:YAG激光具有孔道直、热损伤小的优点。结论 :KTP倍频 Nd:YAG激光是激光心肌血运重建术可供选择的激光源。     

草莓状血管瘤激光治疗的疗效观察

目的:观察应用Nd:YAG激光治疗草莓状血管瘤的疗效。方法:对342例草莓状血管瘤采用Nd:YAG激光对血管瘤病变组织照射或插入治疗,平均治疗2至3次。结果:Nd:YAG激光治疗342例草莓状血管瘤总有效率达到95%以上,对控制血管瘤的发展效果满意。结论:Nd:YAG激光治疗草莓状血管瘤疗效满意,操作方便,安全可靠。     

激光治疗视网膜静脉阻塞疗效评价

目的评价激光治疗视网膜静脉阻塞的疗效.方法对确诊为视网膜静脉阻塞的32例患者行倍频NdYAG激光治疗,随访时间为3～32个月(平均16个月).结果激光治疗后30例有效,总有效率为93.7%,光凝后视力进步者10例(31.3%);视力下降者1例(3.17%);视力不变者21例(65.6%).结论激光治疗视网膜静脉阻塞疗效肯定,可预防其并发症的产生并有效保持患者视力.     

Nd：YAG激光与传统手术治疗会厌囊肿的疗效比较

目的比较NdYAG激光、传统手术治疗会厌囊肿的疗效。方法对60例会厌囊肿分别采用NdYAG激光照射治疗或手术摘除治疗。结果NdYAG激光照射治疗有效率达91%,手术摘除有效率达75%。结论NdYAG激光治疗会厌囊肿优越于手术摘除。     

瘢痕的激光治疗进展

激光治疗瘢痕始于20世纪70年代后期，治疗机理包括去除瘢痕组织：破坏瘢痕内血管：抑制胶原合成：抑制细胞增殖；诱导细胞凋亡等。目前已胡CO2激光、氩离子浓度、Nd:YAG激光、脉冲染料激光等用于临床实践。     

叶绿素、血卟啉致动脉粥样硬化斑块光敏化作用对比研究

以荧光显微镜观察经生理盐水、叶绿素、血叶啉处理人尸粥样斑块及正常血管,发现叶绿素、血卟啉能选择性聚积于动脉粥样硬化斑块。以等量的Nd:YAG倍频激光能量照射,叶绿素、血卟啉处理组斑块激光消融涤度大于对照组斑块消融深度,P<0.01;提示叶绿素、血卟啉是Nd:YAG倍频激光血管成形术的理想光敏剂。     

Nd:YAG激光治疗前列腺的研究

目的：观察Nd:YAG激光对前列腺增生的疗效，探讨激光的作用机理。方法：应用Nd:YAG激光器经膀胱镜插管孔将芯径400μm石英光导纤维送入膀胱，对准增生的前列腺组织，进行烧灼、汽化、切割。手术激光输出功率0－5W，每次照射7－9秒。结果：本组96例经一次Nd:YAG激光治疗，术后三个月，92例排尿正常，自觉症状明显好转，B超显示，残余尿量35ml以下。一年后，膀胱镜检查，前列腺左、中、右三叶肥大均消失，内膜完整光滑。结论：Nd：YAG激光治疗前列腺增生症效果良好，对肥大前列腺组织具有良好的生物效应。     

CO2激光和Nd:YAG激光治疗宫颈糜烂及其疗效对比

目的：比较Nd：YAG激光与CO2激光治疗宫颈糜烂的效果.方法：分别用Nd：YAG激光和CO2激光治疗宫颈糜烂患者用Nd：YAG激光者为治疗组，用CO2激光者为对照组，结果：治疗组一次治愈率为92.2%．总治愈率为99．45％；对照组一次治愈率为82.02%，总治愈率为98％．随访10个月，对照组2例复发，治疗组无复发．结论：Nd：YAG激光治疗宫颈糜烂效果优于CO2激光。