Stable continuous-wave single-frequency intracavity frequency-doubled laser with intensity noise suppressed in audio frequency region

We demonstrated a continuous wave(cw) single-frequency intracavity frequency-doubled Nd:YVO_4/LBO laser with 532 nm output of 7.5 W and 1.06 μm output of 3.1 W, and low intensity noise in audio frequency region.To suppress the intensity noise of the high power 532 nm laser, a laser frequency locking system and a feedback loop based on a Mach-Zehnder interferometer were designed and used.The influences of the frequency stabilization and the crucial parameters of the MZI, such as the power splitting ratio of the beam splitters and the locking state of the MZI, on the intensity noise of the 532 nm laser were investigated in detail.After the experimental optimizations, the laser intensity noise in the frequency region from 0.4 kHz to 10 kHz was significantly suppressed.

Tunable femtosecond laser in the visible range with an intracavity frequency-doubled optical parametric oscillator

We demonstrated experimentally a synchronously pumped intracavity frequency-doubled femtosecond optical para- metric oscillator （OPO） using a periodically-poled lithium niobate （PPLN） as the nonlinear material in combination with a lithium triborate （LBO） as the doubling crystal. A Kerr-lens-mode-locked （KLM） Ti：sapphire oscillator at the wavelength of 790 nm was used as the pump source, which was capable of generating pulses with a duration as short as 117 fs. A tunable femtosecond laser covering the 624-672 nm range was realized by conveniently adjusting the OPO cavity length. A maximum average output power of 260 mW in the visible range was obtained at the pump power of 2.2 W, with a typical pulse duration of 205 fs assuming a sech2 pulse profile.

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.

Modelling of passively Q-switched lasers with intracavity Raman conversion

We present a model of passively Q-switched Raman lasers by utilizing the rate equations. The intracavity fun-damental photon density, Raman photon density and the initial population-inversion density of the gain medium are assumed to be of Gaussian spatial distributions. These rate equations are normalized by introducing some synthetic parameters and solved numerically, and a group of general curves are generated. Prom these curves we can understand the dependence of the Raman laser pulse characteristics on the parameters about the pumping, the gain medium, the Raman medium and the resonator. An illustrative calculation for a passively Q-switched Nd^3＋：GdVO4 self-Raman laser is presented to demonstrate the usage of the curves and related formulas.

Development and Research on All-solid-state Intracavity Sum-frequency laser

Generation of intracavity multi-wavelength and the basic principle of sum-frequency lasers are discused, and the current research status and development of laser diode pumped lasers are introduced in detail.

A continuous-wave Nd:YVO_(4)-KGW intracavity Raman laser with over 34% diode-to-Stokes optical efficiency

We demonstrate a continuous-wave(CW)Nd:YVO_(4)-potassium gadolinium tungstate(KGW)intracavity Raman laser with a diode-to-Stokes optical efficiency of 34.2%.By optimizing the cavity arrangement and reducing the cavity losses,8.47 W Stokes output at 1177 nm was obtained under an incident 878.6 nm diode pump power of 24.8 W.The influence of cavity losses on the power and efficiency of the CW Raman laser,as well as the potential for further optimization,was investigated based on the numerical model.The observation of thermally-induced output rollover was well explained by the calculation of the thermal lensing and cavity stability,indicating that the end-face curvature played an important role when the end-face of the crystal was highly reflective coated to make the cavity.A 10.9 W Stokes output under 40.9 W incident pump was also demonstrated with a cavity arrangement less sensitive to the end-face curvature,which is the highest output power of CW intracavity Raman lasers reported.

High efficiency continuous-wave tunable signal output of an intracavity singly resonant optical parametric oscillator based on periodically poled lithium niobate

In this paper we report on a continuous-wave （CW） intracavity singly resonant optical parametric oscillator （ICSRO） based on periodically poled LiNbO3 （PPLN） pumped by a diode-end-pumped CW Nd：YVO4 laser. Considering the thermal lens effects and diffraction loss, an optical ballast lens and a near-concentric cavity are adopted for better operation. Through varying the grating period and the temperature, the tunable signal output from 1406 nm to 1513 nm is obtained. At a PPLN grating period of 29 pm and a temperature of 413 K, a maximum signal output power of 820 mW at 1500 nm is achieved when the 808 nm pump power is 10.9 W, leading to an optical-to-optical conversion efficiency of 7.51%.

High efficiency,low threshold,high repetition rate H-βFraunhofer line light at 486.1 nm generation by an intracavity frequency-doubled optical parametric oscillator

A high efficiency,low threshold,high repetition rate H-βFraunhofer line light at 486.1 nm was demonstrated.A high-efficiency KTP optical parametric oscillator was achieved by double-pass pumping with a high-maturity 5 kHz 532 nm laser.Thanks to the efficient intracavity frequency doubling of the circulating signal wave by a BIBO crystal,the threshold pump power of the 486.1 nm output was 0.9 W,and the maximum output power of 1.6 W was achieved under the pump power of7.5 W.The optical–optical conversion efficiency was 21.3%,with the pulse duration of 45.2 ns,linewidth of~0.12 nm,and beam quality factor M~2 of 2.83.

聚多卡醇联合腔内激光在下肢静脉曲张患者中的应用效果

目的:探讨聚多卡醇联合腔内激光治疗下肢静脉曲张患者的效果。方法:选择2022年1月—2023年12月于龙岩市第二医院进行治疗的96例下肢静脉曲张患者作为研究对象,随机分为对照组和观察组,各48例。对照组行大隐静脉高位结扎联合分段剥脱术治疗,观察组采用腔内激光闭合术联合聚多卡醇治疗。比较两组的凝血功能指标、静脉临床严重程度评分(VCSS)、应激功能指标、血管内皮功能指标及并发症发生情况。结果:治疗前,两组凝血功能指标、VCSS评分、应激功能指标、血管内皮功能指标比较,差异无统计学意义(P>0.05)。治疗后,两组血浆纤维蛋白原(FIB)、纤溶酶原激活物抑制物(PAI-1)、VCSS、超氧化物歧化酶(SOD)、血清内皮素-1(ET-1)及外周血循环内皮细胞(CEC)低于治疗前,纤溶酶原激活物(t-PA)、血清丙二醛(MDA)、一氧化氮(NO)水平高于治疗前,且观察组FIB、PAI-1、VCSS、MDA、ET-1及CEC水平低于对照组,t-PA、SOD、NO水平高于对照组,差异有统计学意义(P<0.05)。治疗后,观察组并发症总发生率低于对照组,差异有统计学意义(P<0.05)。结论:下肢静脉曲张患者采用聚多卡醇联合腔内激光治疗可以有效缓解症状,改善凝血功能,降低并发症发生率。

Study on 660-nm quasi-continuous-wave intracavity frequency-doubled NdrYAG laser

A quasi-continuous-wave intracavity frequency-doubled Nd:YAG laser which operates at 660 nm is studied. By using a flat-flat laser cavity, 2 Kr-lamps, KTP crystal and an acousto-optically Q-switch, 2-W output power at 660 nm is obtained. The relationship between laser cavity length and output power is analyzed.

Theory of intracavity-frequency-doubled solid-state four-level lasers

The spatial distributions of the pumping, the population inversion density, and the intracavity photon densities of the fundamental and the second harmonic are taken into account in the rate equations of the intracavity-frequency-doubled cw lasers. By normalizing the related parameters, it is shown that the general solution of these space-dependent rate equations is dependent upon three dimensionless paramenters: the pump to laser-mode size ratio, the normalized pump level, and a parameter written as ηSHG, which is related to the ability of the nonlinear crystal to convert the fundamental to the second harmonic. By numerically solving these rate equations, a group of general curves are obtained to express the relations between the solution and the three dimensioniess parameters. In addition, the optimal pump to laser-mode size ratio and the optimal ηSHG are determined. A comparison with the result obtained under the plane-wave approximation is also given.

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%.

Theory of intracavity-frequency-doubled quasi-three-level cw lasers

The rate equations for the intracavity-frequency-doubled quasi-three-level lasers are developed. By normalizing the related parameters, it is shown that the general solution to the rate equations is dependent upon four dimensionless parameters: the normalized reabsorption loss, the pump to laser-mode size ratio, the normalized pump level, and a parameter written as nSHG, which is related to the ability of the nonlinear crystal to convert the fundamental to the second harmonic. By numerically solving these rate equations, a group of general curves are obtained to express the relations between the solution and the four dimensionless parameters.

腔内倍频454 nm脉冲蓝光Nd∶YLF激光器

面向海洋激光应用,针对LD端面抽运的紧凑型准三能级Nd∶YLF晶体激光器实现454 nm蓝光激光脉冲输出特性开展了实验研究。设计了两种方案,电光调Q法和增益调制法,获得454 nm蓝光脉冲激光输出。在增益调制方法中,当重复频率为100 Hz时,Nd∶YLF晶体激光器腔内倍频获得了最大功率为3.16 mW的454 nm蓝光脉冲激光输出,脉冲宽度约为418 ns。而在电光调Q方法中,100 Hz的重复频率下,腔内倍频454 nm蓝光脉冲输出平均功率最大为23.62 mW,脉冲宽度约为66 ns,倍频效率约为3.7%。该研究为获得高重复频率、百纳秒脉宽的紧凑型蓝光454 nm波长脉冲激光提供参考。

高转换效率腔内倍频外腔面发射蓝光激光器

高功率高光束质量的蓝色激光在激光显示与照明、水下通信和成像、有色金属加工等许多领域具有广泛应用前景.本文利用增益芯片底部的高反镜分布布拉格反射镜、折叠镜以及后端反射镜构成V型谐振腔,通过腔内插入非线性晶体LBO,获得了高转换效率的高功率、高光束质量蓝光输出.实验研究了非线性晶体的长度、基频激光的线宽、倍频走离角的补偿等不同因素对外腔面发射激光器腔内倍频蓝光输出功率的影响.在LBO的Ⅰ类相位匹配条件下,当晶体长度为5 mm,所用双折射滤波片厚度为1 mm时,获得超过6 W的491 nm波长蓝光输出,x和y方向的光束质量M2因子均为1.08,倍频转换效率为63%.

四妙勇安汤加减联合激光腔内闭合术治疗下肢静脉曲张临床研究

目的:观察四妙勇安汤加减联合激光腔内闭合术治疗下肢静脉曲张的效果。方法:84例按随机数字表法分为两组各42例。两组均予以激光腔内闭合术治疗,观察组加用四妙勇安汤加减治疗。结果:观察组治疗后VCSS评分、AVVQ评分低于对照组(P<0.05),BI评分高于对照组(P<0.05)。观察组治疗后HBV、PV、LBV、FIB低于对照组(P<0.05)。观察组治疗后皮肤瘙痒、酸胀疼痛、皮肤色素沉着、口渴不欲饮积分低于对照组(P<0.05)。观察组治疗后生活质量各领域评分高于对照组(P<0.05);观察组并发症少于对照组(P<0.05)。结论:四妙勇安汤加减联合激光腔内闭合术治疗下肢静脉曲张可提高疗效,减少并发症。

Management hepatolithiasis with operative choledochoscopic FREDDY laser lithotripsy combined with or without hepatectomy

BACKGROUND: Hepatolithiasis is very common in East Asia. It is benign in nature, but has a high recurrence rate. It is likely to lead to biliary cirrhosis and increase the risk of cholangiocarcinoma. Hence, the treatment of hepatolithiasis is difficult but vital. In this report, we present a novel approach to manage hepatolithiasis using the choledochoscopic Frequency-Doubled Double pulse Nd:YAG (FREDDY) laser lithotripsy combined with or without hepatectomy. METHODS: Between July 2009 and October 2012, 45 patients underwent choledochoscopic FREDDY laser lithotripsy combined with or without hepatectomy (laser lithotripsy group). Fortyeight patients underwent a traditional operation (traditional method group) from January 2009 to June 2009. Comparative analysis was made of demographic and clinical characteristics of the two groups. RESULTS: The final stone clearance rate of the laser lithotripsy group was 93.3%, whereas that of the traditional method group was 85.4% (P=0.22). In the laser lithotripsy group, 2 patients experienced hemobilia and 3 patients had acute cholangitis. In the traditional method group, 3 patients had intraoperative hemorrhage, 1 patient had bile leakage, 6 patients had acute cholangitis, and 1 patient died of liver failure. Moreover, the operative time in the traditional method group was significantly longer than that in the laser lithotripsy group (P=0.01). The mean hospital stay of the patients in the traditional method group was longer than that in the laser lithotripsy group (9.8 vs8.2 days, P=0.17). Recurrent intrahepatic bile duct stones were not found during the follow-up period in the two groups. CONCLUSION: Operative choledochoscopic FREDDY laser lithotripsy combined with or without hepatectomy may be an effective and safe treatment for hepatolithiasis.

Tunable femtosecond near-infrared source based on a Yb:LYSO-laser-pumped optical parametric oscillator

We demonstrate a widely tunable near-infrared source from 767 nm to 874 nm generated by the intracavity second harmonic generation （SHG） in an optical parametric oscillator pumped by a Yb：LYSO solid-state laser. The home-made Yb：LYSO oscillator centered at 1035 nm delivers an average power of 2 W and a pulse duration as short as 351 fs. TWo MgO doped periodically poled lithium niobates （MgO：PPLN） with grating periods of 28.5-31.5 μm in steps of 0.5 μm and 19.5-21.3μm in steps of 0.2 μm are used for the OPO and intracavity SHG, respectively. The maximum average output power of 180 mW at 798 nm was obtained and the output pulses have pulse duration of 313 fs at 792 nm if a sech2-pulse shape was assumed. In addition, tunable signal femtosecond pulses from 1428 nm to 1763 nm are also realized with the maximum average power of 355 mW at 1628 nm.

Compact Diode-Pumped Continuous-Wave Nd：LuVO4 Lasers Operated at 916 nm and 458 nm

We report the compact diode-pumped continuous-wave （CW） Nd：LuV04 lasers operated at 916nm and 458nm for the first time. The maximum output power of 780mW at 916nm laser is obtained with a slope efficiency of 9.3%. We generate 50roW of 458nm blue laser employing a type-Ⅰ critical phase-matched LBO crystal.

A single-longitudinal-mode continuous-wave Ho-(3＋)：YVO4 laser at 2.05 μm pumped by a Tm-fibre laser

We present a single-longitudinal-mode continuous-wave Ho^3＋：YVO4 laser at 2.05 μm pumped by a Tm-doped fibre laser. Use of a cavity etalon enables spectral selectivity for single-mode operation. The highest power achieved in the single longitudinal mode at 2052.5 nm is 282 mW at a slope efficiency of 6.9%, corresponding to an optical conversion efficiency of 3.0%. These features demonstrate that this single-longitudinal-mode Ho：YVO4 laser is suitable for use as a seed laser in some Lidar systems（e.g., coherent Lidar or differential absorption Lidar）. To the best of our knowledge, this is the first report on such a single-longitudinal-mode Ho：YVO4 laser at 2.05 μm.