YVO4晶体的高效受激拉曼散射

报道了YVO4晶体在532 nm、30 ps脉冲下的的高效受激拉曼散射。采用腔外单次通过方式测量了不同长度YVO4晶体1阶斯托克斯受激拉曼散射的阈值,并得到该晶体的稳态增益系数为16.0±0.5 cm/GW。实验中观察到2阶斯托克斯线(558.6 nm5、87.8 nm)和1阶反斯托克斯线(508.0 nm),受激拉曼散射的整体转换效率高于50%。     

强激光照射下,α-LiIO_3晶体中晶格振动的多模激发和模之间的相互作用

本文叙述了用调Q倍频YAG脉冲激光照射α-LiIO_3晶体,在不同的散射配置下,获得了各种散射谱图。实验表明,当用e光入射时,可以比用o光入射激发起更多不同模的晶格振动;获得了E_2模的很强的一阶、二阶斯托克斯散射线和反斯托克斯散射线,E_1模Polariton的一阶、二阶、三阶斯托克斯线和反斯托克斯线,还获得了反斯托克斯频率区一条频移为469cm~(-1)的新线,认为是不同模的Polariton之间的相互作用引起的。 最后,提到实验中初步观察到的晶体拉曼活性的“疲劳现象”。     

荧光物质光学性质对受激拉曼散射的影响

荧光在受激拉曼散射中能发挥良好的外部种子作用,可以极大幅度降低受激拉曼阈值、增加散射模式的强度。将溶解了荧光物质的CS2溶液作为液芯光纤的芯液体进行荧光增强受激拉曼散射研究。结果表明,很小能量(1.86 mJ)的激光激发就能获得较强的斯托克斯和反斯托克斯拉曼光。以荧光光谱范围较小的罗丹明B(rhodamine B)作为荧光种子,只获得了强度较高的一阶反斯托克斯谱线和强度较低的一阶斯托克斯谱线;以荧光光谱范围很大的β-胡萝卜素(β-carotene)作为荧光种子,很小的抽运能量就获得了7阶斯托克斯光谱。因此可以选用不同光学性质的荧光种子来选择性增强受激拉曼散射的某一散射模式。     

强激光照射下,α-LiIO3晶体中晶格振动的多模激发和模之间的相互作用

本文叙述了用调Q倍频YAG脉冲激光照射α-LiIO₃晶体,在不同的散射配置下,获得了各种散射谱图。实验表明,当用e光入射时,可以比用o光入射激发起更多不同模的晶格振动;获得了E₂模的很强的一阶、二阶斯托克斯散射线和反斯托克斯散射线,E₁模Polariton的一阶、二阶、三阶斯托克斯线和反斯托克斯线,还获得了反斯托克斯频率区一条频移为469cm^-1的新线,认为是不同模的Polariton之间的相互作用引起的。最后,提到实验中初步观察到的晶体拉曼活性的“疲劳现象”。 关键词：     

LDS751染料的受激喇曼散射

报道了用532nm激光抽运LDS751染料产生720—780nm可调谐染料激光输出的同时,观察到喇曼频移为102和45cm-1的反斯托克斯线,前者谱线较强,后者较弱.与这两条强线对应的斯托克斯线未能观察到.另外,还观察到喇曼频移为34cm-1的一级和二级斯托克斯线与反斯托克斯线 关键词： LDS751染料 受激喇曼散射 喇曼位移 斯托克斯线 反斯托克斯线     

外腔式SrWO4拉曼激光器的输出特性研究

研究了外腔式SrWO4拉曼激光器在ns脉冲抽运下的输出特性。利用主动调Q的Nd∶YAG激光器产生的脉冲宽度为11.7 ns,输出能量为80 mJ的激光作为抽运源,拉曼激光谐振腔采用平平腔,实验采用4片对一阶斯托克斯脉冲和二阶斯托克斯脉冲不同反射率的输出耦合镜,测量了输出能量与抽运能量的关系,计算了转换效率与抽运能量的关系。当输出耦合镜对一阶斯托克斯脉冲的反射率为39.9%时,实验得到一阶斯托克斯脉冲的最大能量和转换效率分别为23.9 mJ和36.2%,当输出耦合镜对一阶斯托克斯脉冲和二阶斯托克斯脉冲的反射率分别为80.5%和12.4%时,得到二阶斯托克斯脉冲的最大输出能量和转换效率分别为16.4 mJ和25.4%,典型的一阶斯托克斯脉冲和二阶斯托克斯脉冲的脉冲宽度分别为6.1 ns和5.8 ns。     

斯托克斯脉冲波形对光纤中受激布里渊散射慢光的影响

为了提高受激布里渊散射慢光的延时和抑制脉冲展宽,通过四阶Runge-Kutta法和特征线法对基于光纤的受激布里渊散射耦合方程组进行数值求解,计算了斯托克斯脉冲边沿陡峭程度、功率,宽度对延迟时间以及脉冲展宽因子的影响,提出了在低频范围内适当提高斯托克斯脉冲的边沿陡峭程度,可以优化延时和脉冲展宽因子的方法.该方法可以获得与...     

激光诱导等离子体对水OH伸缩振动受激拉曼散射的影响

利用532 nm脉冲激光进行水的受激拉曼散射研究,通过改变激光焦点与水-空气界面的距离,获得截然不同的OH伸缩振动受激斯托克斯和反斯托克斯谱线.焦点距水-空气界面大于20 mm时,只存在±3400cm-1的斯托克斯和反斯托克斯谱线;焦点距离水-空气界面小于20 mm时,存在±3000和±3400cm-1的斯托克斯和反斯托克斯谱线;继续缩小焦点与水-空气界面的距离,3000 cm-1谱线被增强,而3400 cm-1谱线被削弱.研究结果表明,激光诱导水产生的等离子体增强了局部水分子的氢键,导致OH伸缩振动红移,同时过剩电子增强了水的OH伸缩振动受激拉曼散射.     

反斯托克斯拉曼光谱在BaTiO_3铁电相变研究中的应用

从理论上讨论了一阶和二阶斯托克斯与反斯托克斯拉曼散射截面的温度依赖关系;在２９３Ｋ至４０１Ｋ的温度范围内,测量了ＢａＴｉＯ３单晶斯托克斯和反斯托克斯过程的偏振拉曼光谱;通过对ＢａＴｉＯ３单晶斯托克斯和反斯托克斯拉曼光谱的综合分析,证实在Ｘ（ＺＺ）Ｙ几何配置下测量到的位于２７５和５１４ｃｍ－１处的强峰为一阶拉曼光谱。此结果支持了ＢａＴｉＯ３铁电相变机制的有序—无序模型。     

双折射光纤受激拉曼散射偏光特性的实验研究

对椭圆芯光纤受激拉曼散射偏光特性进行了系统的实验研究。实验巾观察到8级斯托克斯线和2级反斯托克斯线,对不同偏振态的抽运光激励下各级斯托克斯线的偏振特性、拉曼频移等参量进行了分析,并给出了经验公式。其结果与实验数据符合良好。实验表明,双折射光纤受激拉曼谱的各级斯托克斯线的偏振状态不但与拉曼介质有关还与抽运光的偏振态有关,入射抽运光偏振态对低阶次的斯托克斯线拉曼频移的影响较小,而对高级斯托克斯线拉曼频移影响较大。     

Theory of mode pulling in a stokes Raman oscillator. I

In the present paper frequency shifts and other characteristic properties of the Stokes modes in a solid Raman-active sample are investigated theoretically. The Raman process is described by nonlinear Heisenberg equations for running waves, which is convenient in order to satisfy the momentum conservation condition. The Stokes shifted electromagnetic waves are assumed to be reflected at the endfaces of the crystal to establish standing waves (modes), whereas the vibrational waves are treated as running waves because of their large damping. The calculations are done for (a) one mode in the 1. Stokes line, (b) one mode in the 1. and one mode in the 2. Stokes line and (c) two modes in the 1. Stokes line. Case (c) can be established only if the two modes are placed symmetrically with respect to the center of the line. In all three cases homogeneously broadened lines are assumed. The frequency shifts in (a) and (c) are power-independent. Only in (b) the shift of the 1. Stokes mode depends on the incident laser flux. Nonlinear pulling and power-dependent pushing of arbitrarily situated modes in the 1. Stokes line occur if additonal modes oscillate simultaneously in the higher order lines. Detailed calculations of these interesting cases are given in a forthcoming paper.     

斯托克斯和反斯托克斯拉曼位移差与时间反演对称性

首先列出若干Stokes和anti-Stokes位移不对称的事例,并在此基础上指出,如果将anti-Stokes散射严格定义为Stokes散射的时间反演行为,则对于初态或末态具有Kramers简并的体系,Stokes和anti-Stokes散射的拉曼位移可以不同.这是因为时间的正过程和反演过程各对应于不同的跃迁途径,其位移大小的差别与简并能级的分裂值相关.     

Amplification effect on stimulated Brillouin scattering in the S-band forward G652 fiber Raman amplifier

The amplification effects on forward and backward stimulated Brillouin scattering (SBS) lines in the forward pumped S-band distributed G652 fiber Raman amplifier (FRA) have been studied. There is a pump threshold power of Stokes backward stimulated Brillouin scattering (B-SBS) line in the forward pumped G652 FRA, it is about 1 mW. The Stokes B-SBS lines are amplified by FRA and fiber Brillouin Brillouin gain. In experimental work, the saturation gain of the first order Stokes backward SBS line is about 58 dB and the saturation gain of 25-km G652 forward FRA is about 25 dB, so the gain of FBA is about 33 dB. The forward stimulated Brillouin scattering (F-SBS) is generated and amplified in S-band G652 FRA. The stimulated threshold powers of the forward first order Stokes SBS (SB1-), second order Stokes SBS (SB2-), and third order SBS (SB3-) in the forward pumped FRA are 2.3, 1.6, and 1.6 mW,respectively. In experimental work, the saturation gains of SB1-, SB2-, and SB3- are about 38, 62, and 60 dB, respectively. The saturation Raman gain of 25-km G652 forward FRA is about 8.8 dB, so the Brillouin gains of SB1-, SB2-, and SB3- are about 29.2, 53.2, and 51.2 dB, respectively. The forward and backward cascaded SBS lines have been observed.     

Stimulated Raman Stokes scattering influenced by all-trans-β -carotene in liquid-core optical fiber

We demonstrate stimulated Raman Stokes (SRS) scattering of carbon disulfide (CS₂) influenced by a natural dye named all-trans-β-carotene in a liquid-core optical fiber (LCOF). These Stokes emissions can acquire the extra effects of seeding or suppression, both of which result from the optical properties of the carotenoids. Then, the efficient control of the selective developments of the Stokes lines by the natural dyes is available in LCOFs. Especially, the low threshold of the high-order Stokes lines, such as the 2nd Stokes line of CS₂, can be more easily obtained through the seeding effect. The saturation intensity of the 1st Stokes line can be suppressed more when the concentration of all-trans-β-carotene in CS₂ becomes high. Simultaneously, the threshold of the 1st Stokes line increases with the addition of the carotenoids. This result is expected to be worthy of new SRS-based fiber light sources for bio-medicine applications such as photodynamic therapy.     

High-power Raman conversion of a discharge XeCl-laser

Raman conversion of high-power discharge XeCl-laser radiation in hydrogen has been carried out. Simultaneous generation of four Stokes and two anti-Stokes outputs has been observed, every radiation line consisting of two close components, which correspond to the double structure of the pumping line.     

High-order stokes emission from a pulsed spin-flip raman laser at 5 μm

Pulsed spin-flip Raman laser action, up to 3rd Stokes, at 5.3 μm has been observed in n-type InSb using the harmonically doubled output from a compact 50 cm long TEA CO₂ laser as the pump. In addition magnetic field thresholds as low as 350 G have been used for first Stokes output. Spin-flip radiation line widths of 0.02 cm^-1 (full width at half height) were obtained.     

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     

水的低频受激拉曼散射

利用532 nm的脉冲激光进行了水的受激拉曼散射研究. 水的低激发光能量下主要表现为受激Stocks和反Stocks 3426 cm^-1谱线; 在能量大于140 mJ时出现低频率313 cm^-1受激Stocks谱线, 同时出现后向3389和3268 cm^-1 的受激Stocks谱线. 实验结果表明, 在较强的激光作用下, 水的结构表现为冰的Ⅷ相.     

Enhanced stimulated Raman scattering in H<Subscript>2</Subscript> by seeding an SRS line into an H-ɛ Balmer line: Amplification-coupled laser wavelength shifter

The stimulated Raman scattering (SRS) in H₂ gas above the dissociation energy limit was recorded using a 266-nm UV laser. All of the observed Stokes and anti-Stokes SRS lines showed a normal behavior except the third Stokes SRS lines at 397.8 nm, which showed a substantial intensity enhancement of about a 36%-conversion efficiency of the pump energy. This enhancement in the SRS line is attributed to the seeding of the SRS line into the Balmer H-? line at 397 nm in molecular hydrogen. To the best of our knowledge, there is no report of any work on enhanced stimulated Raman scattering in H₂ by the seeding of the H-? Balmer line into the SRS line and attaining a very high intensity at the third Stokes SRS lines at 397.8 nm. The cell pressure and the laser pulse energy dependence of these SRS lines substantiate our explanation.