976 nm激光抽运二氧化硅微球级联拉曼散射激光的研究

利用电极放电产生的电弧高温熔融二氧化硅单锥细纤, 熔融的二氧化硅在表面张力作用下形成表面光滑的微球, 完成高品质因子微球腔的制备. 将976 nm激光通过锥光纤以倏逝场方式高效耦合入微球, 研究具有高能量密度回廊模的微球腔中的三阶非线性现象——受激拉曼散射现象. 在实验中测得了六级级联的拉曼散射激光, 各级拉曼散射激光分别测得单纵模或多纵模; 在抽运光功率不少于582.6 μW时, 测得位于1200 nm附近的拉曼散射激光; 当抽运光功率为3.014 mW时, 测得位于1287.04 nm附近的第六级拉曼散射激光. 关键词： 微球腔 锥光纤 高品质因子 拉曼散射激光     

水中受激拉曼散射的能量增强及受激布里渊散射的光学抑制

为提高液体介质中受激拉曼散射的输出能量,提出了通过温度调控来抑制受激布里渊散射的方法,设计了532 nm多纵模宽带脉冲激光泵浦的受激拉曼散射发生系统,测量了不同温度下水中前向受激拉曼散射及后向受激布里渊散射的输出能量,分析了水温、泵浦激光线宽及热散焦效应对受激拉曼散射输出能量影响的物理机制.实验结果表明:通过降低水温可实现对受激布里渊散射过程的有效抑制,同时减小热散焦效应带来的光束畸变,从而有效提高受激拉曼散射的输出能量.研究结果对液体介质中的受激拉曼散射多波长转换具有重要意义.     

激光诱导等离子体冲击波增强水和重水晶格振动受激拉曼散射

利用532 nm的脉冲激光进行了水和重水受激拉曼散射研究,不仅实现了O—H和O—D的伸缩振动受激拉曼散射,同时还实现了晶格振动的受激拉曼散射。水在激发光能量为130 mJ时出现低频受激Stocks和Anti-Stoks 313 cm-1谱线;重水在激发光能量为160 mJ时出现低频受激Stocks和Anti-Stoks 280 cm-1谱线。利用激光诱导等离子体解释了这种拉曼散射增强模式。     

YbVO4晶体的受激拉曼散射

采用腔外单次通过方式,研究了一种新型晶体YbVO4的受激拉曼散射.当抽运激光为532 nm皮秒脉冲时获得了3级斯托克斯线(558.47 nm,587.92 nm,620.67 nm)和1级反斯托克斯线(507.58 nm),测得YbVO4晶体1级斯托克斯受激拉曼散射的稳态增益系数为17.8 4±O.2 cm/Gw,受激拉曼散射的整体转换效率达到37%.实现了YbVO4晶体对355 nm皮秒激光的受激拉曼散射,观察到1级斯托克斯线(366.11 nm),根据抽运阈值得到相应的拉曼增益为29.0±0.3 cm/GW.     

皮秒激光抽运高压H_2的受激拉曼散射研究

利用Nd :YAG锁模序列脉冲激光 (10 6 4nm)抽运充有高压H2 的拉曼池 ,输出光束经棱镜分光后投射在屏上 ,在可见光及近紫外光区用彩色胶卷摄得 15个受激拉曼散射光斑 ;经 1m光栅摄谱仪摄谱 ,在 36 5— 6 0 5nm波长范围内得到 6 5条受激拉曼谱线 .通过实验结果与理论计算值的比较 ,证明除了H2 的振动拉曼频移量 4 15 4 6cm- 1 外 ,还有多个振动及转动拉曼频移量共同参与作用 ,从而产生了从紫外到红外众多波长的受激拉曼散射光 .     

罗丹明B荧光增强苯受激拉曼散射研究

将液芯光纤技术与荧光增强受激拉曼散射技术相结合,能够大大增强受激拉曼散射光谱强度,降低受激拉曼散射阈值。通过对罗丹明B苯溶液在液芯光纤中的受激拉曼散射进行研究,结果表明:荧光染料Rhodamine B可以降低苯溶液的各阶受激拉曼散射阈值近一个数量级;在一定浓度范围内(10-6mol/L~10-8mol/L)各阶Stokes阈值随浓度降低而降低,并在理论上给出了解释。并且理论推导了在荧光种子作用下的四阶耦合波方程。液芯光纤中的受激拉曼光谱技术在对实现宽带受激辐射激光器、种子激光,以及生物大分子结构研究、生物分子的非生物过程研究等领域等有光明应用前景。     

四磺酸基苯基卟啉荧光增强苯的高阶受激拉曼散射

报道了在液芯光纤内利用四磺酸基苯基卟啉荧光增强苯的高阶受激拉曼散射实验研究. 实验表明:利用荧光效应显著增强苯的高阶受激拉曼谱线的强度;高阶Stokes谱线的阈值明显降低;随着Stokes谱线阶数的增加,Stokes谱线宽度变窄. 用3.55 mJ小能量激光实现了液芯光纤内生物分子荧光增强受激拉曼散射. 此技术对实现宽带受激辐射、种子激光、生物大分子结构研究和生物分子的非生物利用等领域有广阔的应用前景. 关键词： 受激拉曼散射 荧光 液芯光纤     

双包层光纤激光器的受激拉曼散射与热应力

 建立了高功率掺镱双包层光纤激光器的速率方程模型与热应力模型，对影响受激拉曼散射效应和热应力效应的关键参数（如纤芯半径、光纤长度、泵浦波长、泵浦方式）进行了数值模拟。结果表明:对于较小的纤芯半径，光纤内的斯托克斯光功率较大且增长迅速，因此增加纤芯半径能有效减弱受激拉曼散射效应；减小光纤长度能提高受激拉曼散射的阈值，而纤芯的热应力也增大，因此在不出现热应力引起光纤断裂的情况下，可以减小光纤长度以提高输出功率；采用976 nm波段泵浦源能提高输出功率，降低热应力的影响；两端均匀泵浦方式可以有效降低纤芯热应力，同时维持高功率输出。     

皮秒激光抽运高压H2的受激拉曼散射研究

利用NdYAG锁模序列脉冲激光(1064nm)抽运充有高压H2的拉曼池,输出光束经棱镜分光后投射在屏上,在可见光及近紫外光区用彩色胶卷摄得15个受激拉曼散射光斑;经1m光栅摄谱仪摄谱,在365-605nm波长范围内得到65条受激拉曼谱线.通过实验结果与理论计算值的比较,证明除了H2的振动拉曼频移量4154.6cm-1外,还有多个振动及转动拉曼频移量共同参与作用,从而产生了从紫外到红外众多波长的受激拉曼散射光.     

高功率光纤激光受激拉曼散射效应研究新进展北大核心CSCD

由于具有高品质、高效率、高鲁棒性、结构紧凑等优点,光纤激光系统在近20年飞速发展,并得到广泛应用。然而发展至今,依旧存在着一些因素(如非线性效应、热效应、模式不稳定性等)限制着光纤激光系统功率的进一步提升。作为其中的一种主要限制因素,受激拉曼散射效应不仅降低了光纤激光器的输出效率,后向斯托克斯光还会提高系统的损毁风险。最近的研究结果表明,少模光纤中受激拉曼散射在引起模式不稳定性的同时,还会导致准静态的模式退化。因此,需要发展有效的拉曼抑制手段来突破现有瓶颈,促进高功率高光束质量光纤激光发展。在介绍高功率少模光纤激光中受激拉曼散射效应新表征的同时,从高功率光纤激光系统整体优化角度出发,总结整理了相关抑制技术研究新进展,并展望未来可能的研究方向。     

掺Yb$lt;sup$gt;3+$lt;/sup$gt; 磷硅酸盐微球腔发光特性的探究

本文采用双锥光纤与微球腔耦合系统研究成分为 55.93P₂O₅-3.57Al₂O₃-15Na₂CO₃-20SiO₂的掺Yb³⁺ 磷硅酸盐微球腔的合作上转换发光、下转换激光振荡及其级联拉曼激光振荡等发光特性. 本实验采用中心波长为976 nm、线宽为0.15 nm的单纵模半导体激光作为抽运光源,在掺Yb³⁺磷硅酸盐微球腔中测得中心波长为476.1 nm的蓝色合作上转换荧光,并运用合适的理论模型来解释该合作上转换产生11.9 nm蓝移效应的原因. 同时,在1058.26 nm和1060.02–1126.08 nm处分别测得了由于微球腔谐振产生的下转换单纵模及多纵模激光振荡. 另外,本文首次在同一微球腔中测得了由Yb³⁺下转换激光激发产生的多级级联拉曼激光. 在抽运功率为8.53 mW时,产生的级联拉曼激光可以达到两级,且波长延伸至1300 nm附近. 关键词： 3+磷硅酸盐微球腔')" href="#">掺Yb³⁺磷硅酸盐微球腔 合作上转换 下转换激光 自激发级联拉曼激光     

Raman lasing and other nonlinear effects based on ultrahigh-Q CaF2 optical resonator

The calcium fluoride (CaF₂) whispering gallery mode crystalline resonator is an excellent platform for nonlinear optical applications because of the decreasing in threshold caused by ultrahigh quality (Q) factor. In this paper, we achieved the observation of Raman lasing, first-order Raman comb, and second-order Raman lasing in a CaF₂ disk resonator with a diameter of 4.96 mm and an ultrahigh-Q of 8.43× 10⁸ at 1550-nm wavelength. We also observed thermal effects in CaF₂ disk resonator, and the threshold of thermo-optical oscillation is approximately coincident with Raman lasing, since the intracavity power increases rapidly when the power reaches the threshold, and higher input pump power results in longer thermal drift and higher Raman emission power. With a further increase in pump power, the optical frequency combs range is from 1520 nm to 1650 nm, with a wavelength interval of 4× m FSR. It is a promising candidate for optical communication, biological environment monitoring, spectral analysis, and microwave signal sources.     

Nd~(3+)/Yb~(3+)共掺磷酸盐玻璃光纤的发光与激光特性研究

以970 nm和808 nm半导体激光器作为抽运源,从光纤长度和抽运功率两个方面,探讨了Nd~(3+)/Yb~(3+)摩尔浓度比约为4:1的共掺磷酸盐玻璃光纤的发光与激光特性.在970 nm抽运下,光纤光谱以Yb~(3+)离子的发光为主,但Yb~(3+)→Nd~(3+)能量传递会对光纤光谱(激光和受激放大自发辐射)产生调制作用,调制作用随970 nm抽运功率或光纤长度的增加而显著,甚至出现显著的双波长激光现象.尽管玻璃样品中Nd~(3+)→Yb~(3+)的能量传递效率ηNd→Yb高达64%,但在808 nm抽运下,激光峰始终在1053 nm附近产生,且与808 nm抽运功率大小和光纤长度无关.为解释这一现象,推导了考虑Nd~(3+)离子受激辐射的能量传递模型.从理论模型来看,Nd~(3+)→Yb~(3+)能量传递作用随Nd~(3+)离子受激辐射信号光强度的增加而迅速减弱,这与该光纤实际测试的荧光光谱随808 nm抽运功率的变化规律相符合.因此,当采用Nd~(3+)离子来敏化Yb~(3+)离子时,需要考虑Nd~(3+)离子的受激辐射对Nd~(3+)→Yb~(3+)能量传递的抑制作用.     

Nd:YSAG单晶的光谱和激光性能

用提拉法生长了(1.5 at.%)Nd~(3+):Y_3Sc_2Al_3O_(12)(YSAG)激光晶体,摇摆曲线表明晶体结晶质量优良.测量了该晶体的吸收和发光光谱,表明其适合成熟的808 nm激光二极管(LD)抽运,其~4F_(3/2)→~4I_(11/2)跃迁最强发射波长为1059 nm,发射截面为1.03×10~(-19)cm~2,同时其激光上能级寿命为253μs,表明Nd:YSAG具有和Nd:YAG相近的效率,但其激光上能级寿命比Nd:YAG长约20μs.以LD抽运2 mm×2 mm×6 mm Nd:YSAG激光棒,激光阈值为0.85 W,最高输出功率为1.1 W,激光斜效率为21.1%,光-光转化效率为18.3%.综合表明Nd:YSAG单晶作为激光性能优良的全固态激光材料,更适合全固态调Q激光输出.     

Fiber-coupled microsphere laser

We demonstrate a 1.5-microm - wavelength fiber laser formed by placement of glass microsphere resonators along a fiber taper. The fiber taper serves the dual purpose of transporting optical pump power into the spheres and extracting the resulting laser emission. A highly doped erbium:ytterbium phosphate glass was used to form microsphere resonant cavities with large gain at 1.5microm . Laser threshold pump powers of 60muW and fiber-coupled output powers as high as 3 muW with single-mode operation were obtained. A bisphere laser system consisting of two microspheres attached to a single fiber taper is also demonstrated.     

太阳光泵浦固体激光阈值的理论分析

为了选择适合太阳光泵浦的激光材料,本文从四能级速率方程出发,综合考虑了太阳辐射带状光谱特性和激光材料对泵浦光吸收能力,建立了太阳光泵浦固体激光理论模型。利用该模型推导得到了单束光侧面泵浦和椭球腔侧面泵浦方式下的泵浦阈值表达式,并结合Nd~3+∶YAG、Nd~3+∶glass、Nd~3+∶Cr~3+∶GSGG(Nd~3+∶Cr~3+∶Gd_3Sc_2Ga_3O_12)、Cr~3+∶BeAl_2O_4和Cr~3+∶Nd~3+∶YAG等激光材料的光谱参数,计算了这些材料的泵浦阈值光强。结果表明:在单束光侧面泵浦和椭球腔侧面泵浦方式下,Nd~3+∶YAG的泵浦阈值光强分别为448个太阳常数和224个太阳常数,是比较适合用太阳光泵浦的激光材料。由于椭球腔的特殊结构,采用椭球腔侧面泵浦激光介质,阈值光强比较低。分析了泵浦阈值光强与材料直径的关系。该模型可用于从现有的激光材料中筛选出在太阳光泵浦下最易输出激光的工作物质。     

Characteristics of Er and Er-Yb-Cr doped phosphate microsphere fibre lasers

In this paper both Er and Er-Yb-Cr doped phosphate microspheres have been successfully created through precise melting of the ends of fibre tapers, drawn, respectively, from Er and Er-Yb-Cr doped phosphate glasses. When coupled with a fibre taper, a microsphere fibre laser cavity can thus be configured creating a system pumped by a 980 nm laser diode and using an optical spectrum analyzer to monitor the spectral characteristics of the laser output. The performance and characteristics of the Er and Er-Yb-Cr microsphere lasers thus created are discussed in detail and cross-compared in this paper. Both lasers have shown low-threshold in terms of the pump power and the laser output wavelengths and a close investigation of the system has shown that the output power and laser stability are closely related to the size of the microsphere, the pump power and the microsphere material composition.     

Highly efficient 1181 nm output from a transversely diode-pumped Nd:KGd(WO4)2 self-stimulating Raman laser

We have achieved high average power Raman output from a compact, diode-pumped, self-stimulating Nd³⁺:KGd(WO₄)₂ Raman laser. Maximum Raman output power of 0.8 W was achieved at a pulse repetition frequency (PRF) of 2 kHz. The optical efficiency from diode to Raman laser was 14%. By generating extra-cavity second harmonics using a LiB₃O₅ crystal, it was possible to produce 0.2 W yellow output. The laser system was simulated numerically using rate equations and the results obtained were in good agreement with the experimental results.     

Development of multi-wavelength microsphere fibre laser system for potential sensor applications

A multi-wavelength microsphere laser system, using a chirped fibre Bragg grating and a microsphere resonator as wavelength-selective elements and a high dopant erbium doped fibre as the gain material, has been successfully demonstrated. The multi-wavelength generation of the laser system arises from both the microsphere whispering gallery mode selection and from the additional Raman scattering inside the microsphere cavity when the erbium laser is operating at resonance with the whispering gallery modes. Through an appropriate design and fabrication of a microsphere and of a fibre taper, a selective multi-wavelength fibre laser has been realized when the pump power is above threshold required. The laser output lines created have shown much narrower linewidths than those from conventional fibre lasers and these characteristics are particularly suitable for the range of sensor applications envisaged in the work.     

Large energy 1341.4 nm Nd: YALO3 pulse laser

On the basis of a measured stimulated emission cross-section for the ⁴F_3/2-⁴I_13/2 transition of the Nd³⁺ ion in a YAP crystal, it is shown that the Nd:YALO₃ crystal is a useful kind of laser crystal to operate in a pulsed laser at 1341.4 nm. Output energy of 5.31 J with an overall efficiency of 1.84% at 1341.4 nm has been achieved by using a 6 mm diameter and 101 mm long A-axis YALO₃ rod with 1 at.% Nd³⁺ ion.