四倍频Nd：YAG激光在高压氢气中的喇曼频移研究

利用Nd:YAG固体激光器四倍频输出(266nm)在高压H₂中的受激喇曼散射获得多波长的激光输出。当泵浦能量一定时,通过改变H₂压力得到了最佳的能量输出,299nm波长的激光能量为3mJ,341nm波长的激光能量输出为6.1mJ,398nm波长的激光能量输出为2.8mJ,239nm波长的激光能量输出为0.8mJ,同时在477nm,595nm,218nm,200nm波段也有能量输出。     

固体三倍频激光在高压H2中受激拉曼散射的实验研究

利用Nd∶YAG激光器的三倍频输出 (35 5nm)在H2 中的受激拉曼散射 (SRS)获得波长在 2 0 4～ 86 7nm范围内的激光输出。当抽运能量为 70mJ时观察到四阶Stokes光和五阶Anti Stokes光 ,其中第一阶Stokes光 (416nm)输出能量为 2 8 7mJ,第二阶Stokes光 (5 0 3nm)输出能量为 16mJ,一阶Anti Stokes光 (30 9nm)输出能量为 3mJ。研究了H2 压力和各阶Stokes光能量的关系 ,同时观察到环行光斑和脉宽压缩现象。     

应用压缩氢的受激喇曼散射实现激光频率宽带调谐

受激喇曼散射(SRS)高功率激光频率转换的重要途径,特别是在近真空紫外波段、近红外、中红外波段更因其具有简便性和高效率而引人注目。由于固体或多数液体对光的吸收和色散,限制了入射光的强度,从而限制了输出的Stokes线及反Stokes线的强度和级数。此外,某些非线性效应较显著的液、固体分子的复杂性,增宽了输出Stokes及反Stokes线的谱线宽度;许多固体和液体的喇曼频移也比较窄,不适合用于频率转换。因此,要利用受激喇曼效应的频移来获得宽范围新波段上的可调谐激光源,往往利用气体中的SRS效应。高压H_2气是有大的     

反共振空芯光纤中氘气受激拉曼散射实验研究

报道了基于反共振空芯光纤的氘气单程和级联受激拉曼散射实验研究,详细分析了反共振空芯光纤中氘气受激拉曼散射的过程,研究了输出光谱和拉曼谱线功率随氘气压强和泵浦激光功率的变化规律,指出降低气压、采用峰值功率相对较低的泵浦脉冲可以有效抑制转动受激拉曼散射,提高振动受激拉曼散射效率。此外,通过进一步设计、拉制传输带位置合适、带宽较窄的反共振空芯光纤,利用1064 nm脉冲激光泵浦,可以实现高效的氘气一阶振动斯托克斯光(1561 nm)和二阶级联振动斯托克斯光(2925 nm)输出。     

Stimulated Raman shifting of the Nd:YAG fourth harmonic (266 nm) inH2, HD, and D2

The dependence of the first Stokes stimulated Raman conversion efficiency of fourth-harmonic radiation from a Nd:YAG laser at 266 nm has been studied for the isotopic species H₂, HD, and D₂ as a function of gas pressure and laser energy using a low numerical aperture (~4.5×10^-3) pumping geometry. While the laser energy threshold for first Stokes conversion is seen to vary significantly between the species it has been found that photon conversion efficiencies of at least 50% can be achieved for all of them for laser pump energies at 266 nm ⩽50 mJ/pulse. This study provides a new measurement of the differential cross section for stimulated Raman scattering in HD of 8.1±2.4×10^-29 cm²/sr at 266 nm and at high pressures, and agreement is found with previous measurements of the cross sections for H₂ and D₂. The results have been used to optimize the laser transmitter system for a differential absorption lidar (DIAL) system to measure tropospheric ozone concentration profiles     

Vacuum ultraviolet anti-Stokes Raman lasers

Anti-Stokes Raman laser schemes in atomic sulphur and selenium are studied, allowing conversion of laser lines out of the 350- 178 nm range into the 200-130 nm range. The necessary population inversion with respect to the atomic metastable¹S0levels is produced by photodissociation of the molecules COS and COSe with F2and ArF laser radiation, respectively. Anti-Stokes laser radiation at 167.5 and 158.7 nm for Se and at 182.0, 148.7, and 148.3 nm for S has been generated. Threshold pump energies of 0.1-20 μJ and output energies up to 5 μJ have been observed. At present, the systems are operated at low pump energies, just above threshold. It is expected that by the use of much higher pump energies and by further improvement of system parameters, output energies in the mJ range at MW peak powers will be possible for the VUV transitions.     

Nd:YAG四倍频激光抽运D2和D2/He受激拉曼散射的实验研究

使用脉冲Nd:YAG四倍频激光抽运充有纯D2气体和D2/He混合气体的拉曼池.实验研究了受激拉曼散射的能量转换效率和能量稳定性与系统主要参量,包括抽运光能量、D2气体压强和加入惰性气体He的关系.实验表明,适量惰性气体He的加入在没有降低一阶斯托克斯散射光(S1,波长:289.04 nm)能量稳定性的前提下,有利于提高其能量转换效率,最大能量转换效率达到22.1%.通过实验分析,得到了受激拉曼散射一阶斯托克斯散射光的能量转化效率和能量稳定性的优化条件.     

Stimulated Raman scattering of XeF* laser radiation in H2--Part II

Stimulated Raman scattering (SRS) experiments in hydrogen have been performed with a collimated beam from ane-beam pumped XeF laser operating at 353 nm. An unstable resonator provided good beam quality at energies of about 1.2 J and pulse lengths of about 320 ns. A folded-path Raman cell allowed cell lengths to be continuously varied up to 11 m at a hydrogen pressure of 10 atm. Energy conversion efficiencies of >45 percent to first Stokes (S1) at 414 nm and >40 percent to second Stokes (S2) at 500 nm were observed with no indication of significant four-wave processes.     

Diode-pumped Q-switched Extra-cavity Frequency-doubled Nd：YVO4/KTP Green Laser

A diode-pumped acousto-optical（A-O） Q-switched extra-cavity frequency-doubled Nd：YVO4/KTP （KTiOPO4） green laser formed with a simple plane-plane cavity has been demonstrated. With the incident pump power of 12.7W, A-O Q-switched average output power at 1064nm was 3.81W with a duration of 25 ns at a repetition rate of 20 kHz, extra-cavity frequency doubling with KTP as the nonlinear crystal yielded the maximum output power of 1. 92 W at 532 nm, the corresponding optical conversion efficiency from 1064nm to 532nm light is 50.4%. The continuous-wave（CW） laser properties of diodepumped Nd：YVO4 crystal operating at 1064nm have been studied. With the incident pump power of 25 W, the maximum CW output power of 13.81 W was obtained with the corresponding optical conversion efficiency of 55.24%.     

VUV generation by high-order CARS

Generation of VUV (vacuum ultraviolet) radiation by stimulated Raman scattering (SRS) in H₂ is studied with collinear irradiation of the first Stokes component simultaneously with pump laser radiation. Improvements of the high-order coherent anti-Stokes Raman scattering (CARS) method over the pure SRS scheme are: generation of higher anti-Stokes (AS) orders, increased conversion efficiency, and considerably better reproducibility. Experimental results are presented to confirm the theoretical analysis     

Laser diode-pumped holmium-doped fluorozirconate glass fiber laserin the green (λ~544-549 nm): power conversion efficiency, pumpacceptance bandwidth, and excited-state kinetics

The green (544-549 nm) Ho-doped fluorozirconate (ZBLAN) glass fiber laser, pumped in the red (λ~6;15 nm) by a high-power (~30 mW) InGaAlP laser diode or a ring dye-laser, has been characterized with regard to power conversion efficiency, fiber core-diameter and length, cavity output coupling, and pump acceptance bandwidth. Fibers doped with ~1200 ppm (by weight) of Ho and having core diameters of 1.7, 3, and 11 μm, and lengths ranging from 12.5 to 86 cm, have been studied in Fabry-Perot resonators having output couplings ranging from 1.545 to 96%. For a 1.7-μm core-diameter fiber, 21 cm in length, the threshold-launched pump power for the diode-pumped fiber laser is 1.9 and 3.5 mW for cavity output couplings of 1.5% and 24%, respectively. These values are the lowest for any upconversion-pumped fiber laser reported to date. Also, the noise and threshold-pumping power properties of the diode-pumped fiber laser are superior to those for its dye-laser-pumped counterpart. The highest laser slope efficiency (>22% with respect to launched pump power) was measured for a 3-μm core-diameter fiber and a cavity output coupling of 24%. The spectral interval over which the launched threshold pump power for this laser is <10 mW is almost 20 nm (637-656 nm). Studies of the fiber laser waveform as a function of pump power reveal competition for population between the ⁵S² and ⁵F₄ states and among the Stark sublevels of the ⁵F₄ manifold. Also, measurements of the output power on individual laser lines of the ⁵F₄, ⁵S₂→ ⁵I₈ (ground) transitions of Ho³⁺:ZBLAN as a function of pump power demonstrate the existence of a loss mechanism at the fiber laser wavelength, presumably due to absorption from ground or the ⁵I_y, ⁶S₂ or ⁵F₄ excited states of the ion     

Efficiency studies of the thallium anti-Stokes Raman laser

Selective photodissociation of TlCl and TlI using 248 nm radiation from a KrF* excimer laser has been used to create a Tl* (6p^{2}Pdeg_{3/2}) metastable state population inversion. Stimulated anti-Stokes Raman emission at 376 nm has been observed using a 532 nm pump laser. Output power at the anti-Stokes wavelength and conversion efficiencies are reported.     

激光二极管泵浦高效Nd:YVO4激光器特性研究脉冲倍频稳频Nd:YAG环形激光器

报道了激光二极管泵浦高效Nd:YVO4激光器输出功率及波长特性的研究。基频光输出230 mW, 光-光转换效率为45%。对激光输出波长和泵浦功率的关系进行了研究, 发现激光器的输出波长随泵浦功率的平均变化率约为1.05×10 -3 nm/mW。利用KTP腔内倍频获得29.8 mW的绿光输出, 光-光转换效率为12.4%。在脉冲稳频Nd:YAG激光器的基础上, 采用辅助的长脉冲网络泵浦和短而强的主脉冲泵浦相结合, 以F-P共焦腔为参考频标, 通过同步搜索补偿稳频技术和截波技术.获得中心频率稳定、频漂小于10 MHz、脉宽100 μs、峰值功率>100 W的无尖峰结构的0.53 μm稳频绿光输出。     

Diode-pumped Q-switched Extra-cavity Frequency-doubled Nd: YVO4/KTP Green Laser

A diode-pumped acousto-optical(A-O) Q-switched extra-cavity frequency-doubled Nd: YVO4/KTP (KTiOPO4) green laser formed with a simple plane-plane cavity has been demonstrated. With the incident pump power of 12. 7 W, A-O Q-switched average output power at 1 064 nm was 3.81 W with a duration of 25 ns at a repetition rate of 20 kHz, extra-cavity frequency doubling with KTP as the nonlinear crystal yielded the maximum output power of 1. 92 W at 532 nm, the corresponding optical conversion efficiency from 1 064 nm to 532 nm light is 50.4%. The continuous-wave(CW) laser properties of diodepumped Nd: YVO4 crystal operating at 1 064 nm have been studied. With the incident pump power of 25 W,the maximum CW output power of 13.81 W was obtained with the corresponding optical conversion efficiency of 55.24%.     

Cladding-pumped fiber laser

Laser emission at 1.06 μm, pump light absorption, laser threshold, slope efficiency, and alignment tolerance as a function of the fiber length have been measured for a cladding-pumped double-clad Nd:glass fiber laser. The fiber laser was pumped with a laser diode emitting at 810 nm. It produced an output power of 15.9 mW at an absorbed pump power of 55.1 mW. This corresponds to an optical-optical conversion efficiency of 38.8%     

Compact all-fiber gas Raman light source based on hydrogen-filled hollow-core photonic crystal fiber pumped with single-mode Q-switched fiber laser

We report a compact all-fiber gas Raman light source based on hydrogen-filled HC-PCF gas cell with a SM Q-switched fiber laser as the Raman pump source. Theoretical model of the hydrogen SRS based on HC-PCF pumped with Q-switched fiber laser is also analyzed. Simulated results show that the Stokes pulse is much narrower than the pump pulse, and both the Stokes pulse duration and conversion efficiency are increased with the pump pulse energy of the same duration pump pulses. The experimental results are in agreement with the theoretical results in change trend. For the 120 ns pump pulses with the repetition rate of 5 kHz, the threshold pump energy and conversion efficiency at the threshold are 1.146 μJ and 2.69%.     

Nd：GdCOB晶体1331.0nm自倍频特性

计算了Nd:GdCOB晶体的相位匹配角。用Datachroom-5000染料脉冲激光作为泵浦源,在Nd:GdCOB晶体中实现了由1331.0nm到665.5nm的自倍频激光运转,阈值能量为14.2mJ;当泵浦能量为25mJ时,665.5nm激光的输出能量为0.62mJ,相应的转换效率为2.5%。     

Nd∶GdCOB晶体1331.0nm自倍频特性

计算了Nd∶GdCOB晶体的相位匹配角.用Datachroom-5000染料脉冲激光作为泵浦源,在Nd∶GdCOB晶体中实现了由1331.0nm到665.5nm的自倍频激光运转,阈值能量为14.2mJ; 当泵浦能量为25mJ时,665.5nm激光的输出能量为0.62mJ,相应的转换效率为2.5%.     

利用半导体光纤环形激光器实现四波混频可调谐波长变化

利用SOA光纤环构成环形激光器 ,对波长为 15 45 1nm的 2 5Gbit/s入射信号进行了四波混频波长变换。采用三级滤波加前置放大器形式成功滤出变换信号 ,向上变换最大距离达 13 8nm。     

Study on picosecond pulse-train multi-wavelength Raman laser operating at two Raman modes without tuning

The Stokes line of multi-mode Raman laser was limited by low conversion efficiency of higher-order Stokes and the competition between pure cascaded stimulated Raman scattering(SRS) and Four-wave-mixing(FWM) process which will deplete the pump of SRS process. Through developed pulse-train synchronously pumping technique and two-Raman-mode operating, the orders of output Stokes was improved. With average power of 220 mW, the developed a Raman laser providing up to 5 orders Stokes output, containing up to 16 laser lines without tuning operating and four-wave-mixing process.