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.

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 Single-Frequency Intracavity Frequency-Doubled Ti:Sapphire Laser around 461 nm

We demonstrate a tunable continuous-wave single frequency intracavity frequency-doubled Ti:sapphire laser.The highest output power of 280 mW at 461.62 nm is obtained by employing a type-I phase-matched BIBO crystal and the peak-to-peak fluctuation of the power is less than±1%within three hours.The frequency stability is better than±2.22 MHz over 10 min when the laser is locked to a confocal Fabry–Perot cavity.A three-plate birefringent filter allows for the tunable range from 457 nm to 467 nm,which covers the absorption line of the strontium atoms(460.86 nm).

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.

Continuous-wave mid-infrared intracavity singly resonant optical parametric oscillator based on periodically poled lithium niobate

This paper reports a continuous-wave （CW） mid-infrared intracavity singly resonant optical parametric oscillator based on periodically poled lithium niobate （PPLN） pumped by a diode-end-pumped CW Nd：YVO4 laser. Considering the thermal lens effects, it adopted an optical ballast lens and the near-concentric cavity for better operation. At the PPLN＇s grating period of 28.5 μm and the temperature of 140℃, the maximum idler output power of 155 mW at 3.86 μm has been achieved when the 808 nm pump power is 8.5 W, leading to an optical-to-optical conversion efficiency of 1.82%.

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%.

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.

Intracavity Spontaneous Parametric Down-Conversion in Bragg Reflection Waveguide Edge Emitting Diode

A four-wavelength Bragg reflection waveguide edge emitting diode based on intracavity spontaneous parametric down-conversion and four-wave mixing （FWM） processes is made. The structure and its tuning characteris- tic are designed by the aid of FDTD mode solution. The laser structure is grown by molecular beam epitaxy and processed to laser diode through the semiconductor manufacturing technology. Fourier transform infrared spectroscopy is applied to record wavelength information. Pump around 1.071 μm, signal around 1.77μm, idler around 2.71 μm and FWM signal around 1.35μm are observed at an injection current of 560mA. The influ- ences of temperature, carrier density and pump wavelength on tuning characteristic are shown numerically and experimentally.

Wideband Tunable Frequency-Doubling Optoelectronic Oscillator Using a Polarization Modulator and an Optical Bandpass Filter

A wideband tunable frequency-doubling optoelectronic oscillator （FD-OEO） is proposed and experimentally demonstrated based on a polarization modulator and an optical bandpass filter （OBPF）. The central frequency of the correspondingly fundamental OEO could be adjusted by tuning the bandwidth and central frequency of the OBPF, which could also be regarded as a photonic-assisted tunable microwave filter. The frequency tuning range of the FD-OEO covers from 9.5 to 32.8？GHz, and the single sideband phase noise of the fundamental signal is lower than -100dBc/Hz at an offset of 10？kHz. Moreover, the frequency stability of the generated signal is investigated by measuring its Allan deviation. The Allan deviation of the generated fundamental signal at 10？GHz is 2.39×10^-9.

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.

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。

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%.

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%.

胸腔镜膈肌折叠术治疗小儿膈膨升2种不同缝线缝合打结法的比较

目的探讨改良Prolene线双头针“U”型缝合联合腔外腔内结合打结法在胸腔镜膈肌折叠术治疗小儿膈膨升中应用的可行性、安全性及手术效果。方法回顾性分析我院2010年5月~2022年5月70例膈膨升行胸腔镜膈肌折叠术的临床资料,根据缝合打结方法的不同分为改良组(改良Prolene线双头针“U”型缝合联合腔外腔内结合打结法,n=30)和常规组(腔内缝合打结法,n=40),比较2组患儿围术期指标及有无线结松开或膈膨升复发等。结果70例手术均顺利完成,无中转开放手术。改良组手术时间明显短于常规组[(35.3±7.4)min vs.(64.7±10.8)min,t=13.521,P=0.000]。2组术中出血量、留置胸腔引流管时间、术后住院时间、术前术中和术后动脉血气pH值、PO_(2)、PCO_(2)和术后术侧膈肌轻微上升等差异无统计学意义(P>0.05)。70例术后随访6~24个月,中位随访时间12个月,均无线结松开和膈膨升复发,无死亡。结论胸腔镜膈肌折叠术治疗小儿膈膨升采用改良Prolene线双头针“U”型缝合联合腔外腔内结合打结法安全可行、疗效确切,且简单易操作,具有一定腔镜手术基础的医生可快速掌握,适宜有条件的医院推广开展。

Reliable intracavity reflection for self-injection locking lasers and microcomb generation

Self-injection locking has emerged as a crucial technique for coherent optical sources,spanning from narrow linewidth lasers to the generation of localized microcombs.This technique involves key components,namely a laser diode and a high-quality cavity that induces narrow-band reflection back into the laser diode.However,in prior studies,the reflection mainly relied on the random intracavity Rayleigh backscattering,rendering it unpredictable and unsuitable for large-scale production and wide-band operation.In this work,we present a simple approach to achieve reliable intracavity reflection for self-injection locking to address this challenge by introducing a Sagnac loop into the cavity.This method guarantees robust reflection for every resonance within a wide operational band without compromising the quality factor or adding complexity to the fabrication process.As a proof of concept,we showcase the robust generation of narrow linewidth lasers and localized microcombs locked to different resonances within a normal-dispersion microcavity.Furthermore,the existence and generation of localized patterns in a normal-dispersion cavity with broadband forward–backward field coupling is first proved,as far as we know,both in simulation and in experiment.Our research offers a transformative approach to self-injection locking and holds great potential for large-scale production.

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,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.

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。

Optical, Mechanical and Laser-induced Damage Threshold Properties of 1064 nm, 532 nm Frequency-doubled Antireflection Coating for LBO

1 064 nm, 532 nm frequency-doubled antireflection （AR） coatings with buffer layer of SiO2 between the coating and the substrate were fabricated by the electron beam evaporation technology on the substrate of lithium triborate （LiB3O5 or LBO） crystals. The residual reflectance of the sample is 0.07% and 0.11% at 1 064 nm and 532 nm, respectively. The adhesion and the laser-induced damage threshold （LIDT） of the sample are greater than 200 mN and 18.6 J/cm2. The strengthening mechanism of adhesion and LIDT of the buffer layer of SiO2 were discussed by considering full plastic indentation and shear theory, and spallation of a plated film induced by thermal shock stress, respectively.

Employing SiO_2 Buffer Layer to Improve Adhesion of the Frequency-doubled Antireflection Coating on LBO

Frequency-doubled antireflection coatings simultaneously effective at 1064 nm and 532 nm were deposited on the lithium triborate （LiB3O5 or LBO） crystals using the electron beam evaporation method. Comparing with the sample without buffer layer, it is found that the adhesion of the sample with buffer layer of SiO2 between coating and LBO substrate is improved significantly from 137.4 mN to greater than 200 mN. And the laser-induced damage threshold is increased by 20% from 15.1 J/cm^2 to 18.6 J/cm^2. The strengthening mechanism of adhesion of the buffer layer of SiO2 is discussed by considering full plastic indentation and shear theory.