A high-power high-stability Q-switched green laser with intracavity frequency doubling using a diode-pumped composite ceramic Nd:YAG laser

We successfully obtain a high-average-power high-stability Q-switched green laser based on diode-side-pumped composite ceramic Nd：YAG in a straight piano-concave cavity. The temperature distribution in composite ceramic Nd：YAG crystal is numerically analyzed and compared with that of conventional Nd：YAG crystal. By using a composite ceramic Nd：YAG rod and a type-II high gray track resistance KTP （HGTR-KTP） crystal, a green laser with an average output power of 165 W is obtained at a repetition rate of 25 kHz, with a diode-to-green optical conversion of 14.68%, and a pulse width of 162 ns. To the best of our knowledge, both the output power and optical-to-optical efficiency are the highest values for green laser systems with intracavity frequency doubling of this novel composite ceramic Nd：YAG laser to date. The power fluctuation at around 160 W is lower than 0.3% in 2.5 hours.

Diode end-pumped self-Q-switched and mode-locked Nd,Cr：YAG /KTP green laser

We first experimentally demonstrate a laser-diode end-pumped self-Q-switched and mode-locked Nd,Cr：YAG green laser with a KTP crystal as the intra-cavity frequency doubler. The device produces an average output power of 680 mW at 532 nm. The corresponding pulse width of the Q-switched envelope of the green laser is 170 ＋ 20 ns. The mode-locked pulses have a repetition rate of approximately 183 MHz and the average pulse duration is estimated to be around sub-nanosecond. It is found that the intra-cavity frequency doubling greatly improves the modulation depth and stability of the mode-locked pulses within the Q-switched envelope.

LD Pumped High Efficient Intracavity Frequency-Doubled Green Laser

A laser diode (LD) pumped Q switched high efficient intracavity frequency doubled Nd ∶YAG laser is reported here. The authors have designed an optical coupler and pointed out that the key to increasing harmonic conversion efficiency is to decrease the loss of fundamental wave. In the experiments, a fundamental mode output laser was acquired. When the pumping power was 12 W, 2.6 W average output power at 1 064 nm with AO Q switch was obtained. 2.1 W average output power at 532 nm was obtained with intracavity frequency doubling, and the highest second harmonic conversion efficiency was 82 0 0.

Effect of inhomogeneous broadening on threshold current of GaN-based green laser diodes

The inhomogeneous broadening parameter and the internal loss of green LDs are determined by experiments and theoretical fitting. It is found that the inhomogeneous broadening plays an important role on the threshold current density of green LDs. The green LD with large inhomogeneous broadening even cannot lase. Therefore, reducing inhomogeneous broadening is a key issue to improve the performance of green LDs.

Infrared Laser Pumped Green and Blue Laser Emissions from a Single Solid State Material Doped by Rare Earth Ions

The possible ways and progress of infrared or red laser pumped green and blue laser emissions from a single solid state material doped by rare earth ions are outlined. The green and blue lasers realized from infrared laser pumped rare earth doped nonlinear laser crystals by means of self frequency conversion and from infrared laser pumped rare earth doped bulk, fiber and microsphere materials by means of frequency upconversion are introduced in detail. Other kinds of devices and methods are also compared. The typical nonlinear laser crystals such as YAl 3(BO 3) 4, GdAl 3(BO 3) 4, YCa 4O(BO 3) 3 , GdCa 4O(BO 3) 3, and the typical upconversion fluoride fibers are compared and analyzed. The major problems remaining to be solved and the developing trends in the area are also discussed.

Selective Laser Melting of Novel SiC and TiC Strengthen 7075 Aluminum Powders for Anti-Cracks Application

The aerospace and military sectors have widely used AA7075, a type of 7075 aluminum alloy, due to its exceptional mechanical performance. Selective laser melting (SLM) is a highly effective method for producing intricate metallic components, particularly in the case of aluminum alloys like Al-Si-Mg. Nevertheless, the production of high-strength AA7075 by SLM is challenging because of its susceptibility to heat cracking and elemental vaporization. In this study, AA7075 powders were mechanically mixed with SiC and TiC particles. Subsequently, this new type of AA7075 powder was effectively utilized in green laser printing to create solid components with fine-grain strengthening microstructures consisting of equiaxial grains. These as-printed parts exhibit a tensile strength of up to 350 MPa and a ductility exceeding 2.1%. Hardness also increases with the increasing content of mixed powder, highlighting the essential role of SiC and TiC in SLM for improved hardness and tensile strength performance. .

Green Vertical‑Cavity Surface‑Emitting Lasers Based on InGaN Quantum Dots and Short Cavity

Room temperature low threshold lasing of green GaNbased vertical cavity surface emitting laser(VCSEL)was demonstrated under continuous wave(CW)operation.By using self-formed InGaN quantum dots(QDs)as the active region,the VCSEL emitting at 524.0 nm has a threshold current density of 51.97 A cm^(-2),the lowest ever reported.The QD epitaxial wafer featured with a high IQE of 69.94%and theδ-function-like density of states plays an important role in achieving low threshold current.Besides,a short cavity of the device(~4.0λ)is vital to enhance the spontaneous emission coupling factor to 0.094,increase the gain coefficient factor,and decrease the optical loss.To improve heat dissipation,AlN layer was used as the current confinement layer and electroplated copper plate was used to replace metal bonding.The results provide important guidance to achieving high performance GaN-based VCSELs.

Design of 20 W fiber-coupled green laser diode by Zemax

We represent a design of a 20 W, fiber-coupled diode laser module based on 26 single emitters at 520 nm. The module can produce more than 20 W output power from a standard fiber with core diameter of 400 Hm and numerical aperture （NA） of 0.22. To achieve a 20 W laser beam, the spatial beam combination and polarization beam combination by polarization beam splitter are used to combine output of 26 single emitters into a single beam, and then an aspheric lens is used to couple the combined beam into an optical fiber. The simulation shows that the total coupling efficiency is more than 95%.

Research Progress on High-Density Optical Storage Materials for Blue-Green Laser Recording

The key for the development of high -density optical storage technology nowadays is to develop short wavelength (blue-green laser) recording media and devices. Based on the progress achieved in the key program of National Natural Science Foundation of China "high-density optical storage materials using blue -green laser recording", the chemical composition, microstructure, storage performance and related mechanisms of some kinds of novel high density optical storage materials are presented in this paper. The research method and clew for super high -density optical storage materials and technologies are highlighted.

High-Power Diode-Side-Pumped Intracavity-Frequency-Doubled Continuous Wave 532 nm Laser

An efficient and high-power diode-side-pumped cw 532nm green laser based on a V-shaped cavity geometry, and capable of generating 22.7 W green radiation with opticM conversion effciency of 8.31%, has been demonstrated. The laser is operated with rms noise amplitude of less than 1% and with M2-parameter of about 6.45 at the top of the output power. This laser has the potential for scaling to much higher output power.

Laser treatment in 341 patients with exudative agerelated macular degeneration

AIM:To document the prognosis of laser treatment in patients with exudative age-related macular degeneration(AMD).· METHODS:Efficacy of the intervention was evaluated using a before-after method.· RESULTS:A total of 392 eyes of 341 patients with exudative AMD were examined.77.6% had choroideal neovascularisation(CNV).Before the use of indocyanine green(ICG) angiography,occult CNV was detected in only 1.8% of the eyes,but after the use of ICG angiography,this increased to 19.5%(P<0.001).Of the 349 eyes which were followed up,visual acuity had remained stable in 68.2% of the eyes.There was a statistically significant relationship between localisation of lesion and visual acuity changes on pre-and post-laser treatment(P<0.001).Also there was a statistically significant relationship between localisation of lesion and recurrence(P<0.05).The recurrence was less in subfoveal lesions than that in juxtafoveal and extrafoveal lesions.· CONCLUSION:ICG angiography is highly important in the treatment of occult CNV.

Comparison of three fluorescence labeling and tracking methods of endothelial progenitor cells in laser-injured retina

AIM： To compare three kinds of fluorescent probes for in vitro labeling and in vivo tracking of endothelial progenitor cells（EPCs） in a mouse model of laser-induced retinal injury.METHODS： EPCs were isolated from human umbilical cord blood mononuclear cells and labeled with three different fluorescent probes： 5-（and-6）-carboxyfluorescein diacetate succinimidyl ester（CFSE）, 1,1′-dilinoleyl-3,3,3′,3′-tetramethylindo-carbocyanine perchlorate linked acetylated low-density lipoprotein（Di I-Ac LDL）, and green fluorescent protein（GFP）. The fluorescent intensity of EPCs was examined by confocal microscopy. Survival rate of labeled EPCs was calculated with trypan blue staining, and their adhesive capability was assessed. A mouse model of retinal injury was induced by laser, and EPCs were injected into the vitreous cavity. Frozen section and fluorescein angiography on flat-mounted retinal samples was employed to track the labeled EPCs in vivo.RESULTS： EPCs labeled with CFSE and Di I-Ac LDL exhibited an intense green and red fluorescence at the beginning; the fluorescence intensity decreased gradually to 20.23% and 49.99% respectively, after 28 d. On the contrary, the florescent intensity of GFP-labeled EPCs increased in a time-dependent manner. All labeled EPCs showed normal morphology and no significant change in survival and adhesive capability. In the mouse model, transplantation of EPCs showed a protective effect against retinal injury. EPCs labeled with CFSE and Di I-Ac LDL were successfully tracked in mice during the development of retinal injury and repair; however, GFP-labeled EPCs were not detected in the laser-injured mouse retina.CONCLUSION： The three fluorescent markers used in this study have their own set of advantages and disadvantages. CFSE and Di I-Ac LDL are suitable for short-term EPClabeling, while GFP should be used for long-term labeling. The choice of fluorescent markers should be guided by the purpose of the study.

直出式绿激光膀胱肿瘤剜除术与经尿道膀胱肿瘤等离子电切在治疗非肌层浸润性膀胱癌的围手术期疗效的比较

目的比较直出式绿激光膀胱肿瘤剜除术与经尿道膀胱肿瘤等离子电切术治疗非肌层浸润性膀胱癌(NMIBC)的疗效。方法回顾性分析2019年3月至2020年3月于安庆市立医院泌尿外科治疗的80例NMIBC患者的临床资料,通过随机数表法将80例患者均分为两组,其中实验组采用直出式绿激光膀胱肿瘤剜除术,对照组采用经尿道膀胱肿瘤等离子电切术。对两组的术中出血量、术后膀胱冲洗时间、留置尿管时间、术后住院时间以及术中、术后并发症发生情况进行比较分析。结果两组患者手术均顺利完成,实验组在手术时间、复发率方面与对照组相比差异无统计学意义(P>0.05)。实验组术中出血量、术后膀胱冲洗时间、留置尿管时间、术后住院时间小于对照组;实验组在术后出血、闭孔神经反射和膀胱穿孔发生率明显低于对照组,差异有统计学意义(P<0.05)。结论直出式绿激光膀胱肿瘤剜除术治疗NMIBC较经尿道膀胱肿瘤等离子电切术更安全、有效,具有微创、出血少、并发症风险低等优点,值得临床推广使用。

Electron transport for a laser-irradiated quantum channel with Rashba spin-orbit coupling

We investigate theoretically the electron transport for a two-level quantum channel （wire） with Rashba spinorbit coupling under the irradiation of a longitudinally-polarized external laser field at low temperatures. Using the method of equation of motion for Keldysh nonequilibrium Green function, we examine the time-averaged spin polarized conductance for the system with photon polarization parallel to the wire direction. By analytical analysis and a few numerical examples, the interplay effects of the external laser field and the Rashba spin-orbit coupling on the spinpolarized conductance for the system are demonstrated and discussed. It is found that the longitudinally-polarized laser field can adjust the spin polarization rate and produce some photon sideband resonances of the conductance for the system.

509 nm高功率宽调谐外腔面发射激光器

报道了一种高功率宽调谐外腔面发射绿光激光器,利用设计的1018 nm半导体增益芯片、折叠镜以及后端镜构成结构紧凑的V型腔,使用长度为10 mm的Ⅰ类相位匹配三硼酸锂(LiB_(3)O_(5),LBO)非线性频率变换晶体进行腔内倍频,实现了509 nm波长的高功率绿光输出.通过在腔内插入双折射滤波片(birefringent filter,BRF),可获得连续调谐的激光波长.当BRF厚度为1 mm时,基频激光和倍频绿光的波长调谐范围分别为47.1 nm和20.1 nm.可调谐绿光的最大输出功率为8.23 W,对应的倍频转换效率为68.2%,相应的从吸收泵浦光到倍频绿光的光-光转换效率为16.6%.

不同经尿道前列腺切除术治疗良性前列腺增生的疗效与安全性分析

目的探究不同经尿道前列腺切除术治疗良性前列腺增生的疗效与安全性分析。方法选取2021年1月至2023年5月本院收治的良性前列腺增生患者215例临床资料开展回顾性分析,根据手术方式分为经尿道前列腺等离子电切术治疗的等离子电切术组(n=81)、经尿道前列腺激光切除术治疗的激光切除术组(n=92)、经尿道前列腺绿激光剜除术治疗的绿激光剜除术组(n=42),比较三组围手术期指标(手术时间、术中出血量、膀胱冲洗时间、留置尿管时间、术后血红蛋白浓度、住院时间)、尿动力学指标(RUV、IPSS评分、Qmax、QOL评分)、术后并发症发生情况的差异。结果绿激光剜除术组、激光切除术组总有效率高于等离子电切术组(P<0.05)。3组住院时间比较差异无统计学意义(P>0.05),但绿激光剜除术组手术时间>激光切除术组>等离子电切术组(P<0.05),绿激光剜除术组、激光切除术组术中出血量、膀胱冲洗时间、留置尿管时间<等离子电切术组,且术后血红蛋白浓度>等离子电切术组(P<0.05)。重复测量方差分析结果显示,3组术后1个月、术后3个月RUV、IPSS评分、QOL评分与术前相比均降低,而Qmax与术前相比均升高(P<0.05),且激光切除术组与绿激光剜除术组术后1个月、术后3个月RUV、IPSS评分、QOL评分均低于等离子电切术组,Qmax均高于等离子电切术组(P<0.05),但激光切除术组与绿激光剜除术组术后1个月、术后3个月RUV、IPSS评分、Qmax、QOL评分比较差异无统计学意义(P>0.05)。绿激光剜除术组术后并发症总发生率<激光切除术组<等离子电切术组(7.14%vs.21.74%vs.35.80%,P<0.05)。结论3种手术方式治疗良性前列腺增生均具有较好疗效,但经尿道前列腺激光切除术与绿激光剜除术疗效与安全性均优于经尿道前列腺等离子电切术,可促进患者早期康复,且经尿道前列腺绿激光剜除术治疗安全性最好。

基于三维激光点云数据的校园绿地乔木三维绿量对比研究——以广西生态工程职业技术学院为例

树冠是指树干以上连同其生枝叶的部分,其体积的大小是估算树木三维绿量的重要参数。校园绿地中乔木树冠形态各异,结构复杂,树木树冠体积的准确、自动、无损测量是校园绿地调查中的一个重要研究项目。随机抽取广西生态工程职业技术学院内5个树种共计25棵乔木的三维激光点云数据与树木三维绿量冠幅-冠高公式法进行了对比研究。以三维激光扫描仪获取的三维激光点云数据基于不规则三角网法计算乔木树冠体积。计算结果对比表明:测量值与参考值的均方根误差RMSE为2.913、绝对误差最大值为7.22 m3,最小值为0.17 m3;相对误差最大值为11.06%,最小值为0.12%;平均绝对误差为2.20 m3,平均相对误差为3.13%,该算法不用考虑树冠的形状,减少了人为判别导致的差异。因此,以三维激光扫描仪获取点云数据,运用不规则三角网法自动提取校园绿地乔木树冠体积快捷、有效、可推广。

基于Ti3C2Tx-PVA被动调Q的低噪声556 nm腔内倍频黄绿光激光器

采用液相剥离法获得厚度约为3.2 nm、层数约为3至4层的碳化钛纳米片(Ti_(3)C_(2)T_(x)),结合旋涂法制备出Ti_(3)C_(2)T_(x)-聚乙烯醇(Ti_(3)C_(2)T_(x)-PVA)薄膜,并借助拉曼光谱、原子力显微镜和平衡双探测系统对Ti_(3)C_(2)T_(x)纳米片的物相组成、厚度及可饱和吸收性能进行了表征。将Ti_(3)C_(2)T_(x)-PVA薄膜作为可饱和吸收体应用于一种808 nm半导体激光二极管端面泵浦Nd∶YAG陶瓷/LBO腔内倍频的556 nm黄绿激光器中实现被动调Q。在分析布儒斯特偏振器和双折射晶体协同选频滤波机理的基础上,通过两者的协同使用,抑制了1116 nm和1123 nm处光谱腔内振荡并进一步压缩了1112 nm处p-偏振光的纵模个数。在5.1 W最高激光二极管泵浦功率下,获得了平均输出功率为86.2 mW、重复频率为745.8 kHz、脉冲宽度为46 ns的556 nm被动调Q脉冲黄绿激光输出。4 h内测得功率不稳定度和激光噪声仅为±0.39%和0.37%,光束质量评价因子为M2x=1.837和M^(2)^(y)=1.975。Ti_(3)C_(2)T_(x)-PVA薄膜被动调Q结合“布儒斯特偏振器+双折射晶体”协同选频滤波技术方案为开发高稳定性、低噪声脉冲黄绿激光提供有价值的参考。

Cu箔集流体飞秒激光深刻蚀织构化及其对锂离子电池性能的影响

目的 使用飞秒激光在Cu箔表面深刻蚀织构化,制备微纳沟槽结构,提高锂离子电池Si电极循环稳定性。方法 系统研究激光能量密度、单位点有效脉冲数对厚度为9μm的Cu箔的表面形貌和微纳结构的影响规律,根据结果设计不同沟槽密度和沟槽深度的Cu箔,并组装成Si电极锂离子半电池,通过循环测试及循环后电极形貌揭示其稳定性提升的内在机理。结果 最佳的激光能量密度为3.18 J/cm^(2),此时改变单位点有效脉冲数和扫描间距可有效控制刻蚀沟槽的密度和深度。Si电极的循环稳定性随着Cu箔表面沟槽密度和沟槽深度的增加而逐渐提升,当沟槽密度为75%、沟槽深度为6μm时,循环300圈后剩余的容量高达911 mA·h/g,保持率为89%,电极形貌相对最完整、稳定。结论 刻蚀表面纳米结构增加了电极层与集流体之间的黏结强度;微米沟槽结构进一步保护了电极层,缓解了体积膨胀效应。采用Cu箔集流体深刻蚀显著改善了Si电极的剥离和开裂现象,实现了其电化学性能的提升。

可调谐DFB激光器泵浦的PPLN绿色倍频光源

为研制脉冲宽度、重复频率以及输出功率可调谐至单光子级别的可见光波段高重频纳秒级窄脉冲光源,提出了一种基于增益调制型DFB激光器和PPLN晶体的绿色倍频光源设计方案。通过自制的纳秒级高速驱动电路以脉冲方式驱动DFB激光器产生固定波长的泵浦源;利用光纤半导体衰减器调节衰减量,调制泵浦光强度;采用PPLN晶体作为非线性晶体材料,通过其可调谐特性得到准相位匹配的绿色倍频激光输出。实验结果表明,DFB激光器输出的泵浦光功率和中心波长稳定,脉冲宽度1.02 ns~10.25 ns、工作频率1 Hz~10 MHz连续独立可调,泵浦光功率衰减至-44.61 dB时工作于532.96 nm波段的绿色倍频光输出脉冲平均光子数约为384 N,倍频光-光转换效率9.3%。