A类激光器混沌不稳性研究

从单模场与具有均匀加宽增益线的介质的准共振相互作用出发所形成的激光其动力学行为,要由五个变量耦合的方程来描述。即复场振幅E、复介质极化强度P和粒子数反转量D,这组方程与洛仑兹方程的相似性暗示了混沌不稳性的存在。本文研究介质极化强度P和粒子数反转D快速弛豫变化的A类激光器在(A).外注入信号位相频率与腔共振频率共振;(B).外注入信号位相频率与腔共振频率失谐等     

共振线附近极化介质的电磁辐射

在经典力学框架内,把偶极子运动方程化为含有二次项和三次项的非线性微分方程;用多尺度法找到了系统的近似解;讨论了共振线附近极化介质的光电性质。揭示了系统的倍频、分频、和频与差频等效应;导出了介质的一阶和二阶极化系数;分析了系统在ω≈ω0/3附近的共振行为,并计算了它的瞬时辐射强度和平均辐射强度。     

外部荧光种子植入法增强液芯光纤的受激拉曼散射

报道了一种能够增强液芯光纤中的受激拉曼散射的外部荧光种子植入法。在毛细管套液芯光纤之间充入荧光染料,实现染料介质与拉曼介质的分离,从外部植入染料荧光种子线性地放大液芯光纤中的受激拉曼散射的初始光强,有效无污染地增强了液芯光纤中拉曼介质的受激拉曼散射强度。实验结果表明,外部荧光染料浓度为最佳值约为10-6 mol/L时,可使液芯光纤中拉曼介质的各阶斯托克斯线均有最大增强。     

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。     

1,1’—二乙基—2,2’—酞菁氯化物共振—增强拉曼光谱强度的研究

激光拉曼光谱测量的灵敏度比较低,加入银胶体到有机染料水溶液中,可使银胶微粒表面吸附更多的染料分子,造成金属表面样品浓度增高以增强拉曼散射。选择激发谱线使与作品分子共振,测量灵敏度可进一步提高。 本实验使用的样品为1,1’—二乙基—2,2’—酞菁氯化物,结构式为:     

用倾斜的法布里-珀罗标准具来选择离子激光的频率

在理论上和实验上研究了用内腔倾斜的法布里-珀罗标准具，在调谐到放大谱线中心时来选择气体放电激光器的频率条件。既对均匀平面波进行了计算，又考虑到共振腔中的光束高斯场的径向分布。对于在离子激光器中的洛伦兹和多普勒谱线宽度分量之间的典型比值，计算了将所要求的选择器的锐度与非饱和放大系数和激活介质的饱和度有关的曲线。在介质的饱和度极大时标准具的参数是由介质的饱和放大量来确定的，也就是由共振腔中的损耗的水平来确定的。定量地分析了标准具厚度的选择问题。证明，为了保证谱线中心的单频振荡，标准具的光学厚度不应当超过最大的允许值，在此情况下，标准具的允许范围等于过剩放大区宽度的一半，过剩放大区是由工作频率上的损耗水平来确定的。用有介质反射层的石英标准具的氩激光器，在λ=488亳微米谱线上进行了实验，表明其结果与理论值很好地符合。     

低强度He-Ne激光照射水稻的显微拉曼散射研究

介绍了用显微拉曼研究经低强度He-Ne激光照射。并在均匀磁场中处理过的水稻的结果。并与未经处理水稻的拉曼光谱进行了比较。基本依据是激光对生物分子的共振激发作用理论。从实验结果看．其间的谱线有一定差异，表明激光照射和均匀磁场处理，有可能改变水稻的遗传特性。     

Bloch-Maxwell方程与率方程

阐述光与原子介质相干和非相干共振相互作用的物理内容及其区别从而理解Bloch-Maxwell方程与率方程的关系。     

介质膜波导中有大迴旋半径电子束环的迴旋自共振微波激射器的特性研究

本文用线性化弗拉索夫-麦克斯韦方程分析了介质膜波导中由大迴旋半径电子束环产生的迴旋自共振微波激射器的工作特性。结果表明,介质膜能降低所需的电子束能量,在毫米和亚毫米波段开创了一种新型的有效低压辐射源。     

拉曼带通滤光器压缩强激光背景的应用

采用拉曼带通滤光技术,以调QYAG倍频激光器为激发光源(532nm),在普通单色仪上记录到液相苯的拉曼谱。拉曼带通滤光器(RNF∶Raman Notch Filters)可使杂散光降低10~8量级。应用拉曼带通滤光器直接对YAG倍频输出激光线型进行观察,观察到了与基频相对应的弱跃迁伴线结构。     

A novel technique for suppression of parasitic superfluorescence in backward Raman amplifiers

The major parasitic modes of backward Raman amplifiers are different forms of superfluorescent forward Raman scattering. It is shown that spatial, and/or temporal variation of the Raman frequency in the scattering medium can inhibit amplification of spontaneously scattered light by creating off-resonant conditions in the forward direction. If the frequencies of the optical pulses are properly varied in time (the pulses are chirped), the required resonance condition for amplification of a counterpropagating Stokes wave can be maintained throughout the medium. Raman transition frequencies can be varied in an atomic vapor by application of a magnetic field via the Zeeman effect. The use of thallium (T1) metal vapors for scattering XeCl or KrF excimer laser radiation is considered as a particular example.     

A kilohertz repetition rate 1.9 μm H2 Ramanoscillator

Raman conversion of a high-repetition-rate Q-switched Nd:YAG laser using a gaseous H₂ Raman medium is reported. With a H₂ cell placed in a focusing intracavity Raman oscillator, 3 W of average power at 1.9 μm was obtained from a 15-W 1.06-μm laser operating at 2 kHz. Although the pump beam was multimode, the Stokes output was diffraction limited. At kilohertz repetition rates, conversion efficiencies were improved with a flowing gas cell which substantially reduced the thermal lensing effect in the Raman medium. A rate equation approach was used to model the intracavity conversion process     

分布式光纤喇曼放大器优化算法

提出一种行之有效的优化算法。该方法在喇曼放大器的功率耦合方程基础上 ,通过遗传算法和龙格 -库塔算法的结合 ,对分布式宽带光纤喇曼放大器的性能进行了数值仿真模拟 ,得到了传输距离 1 0 0 km、带宽 70 nm内 ,平均开关增益为 1 5 .2 d B、增益平坦度优于± 0 .7d B的优化结果。     

The Behavior of CARS in Anti-Stokes Raman Converters Operating at Exact Raman Resonance

In this paper, we present a model that fully describes the quasi-stationary behavior of coherent anti-Stokes Raman scattering (CARS) in an anti-Stokes Raman converter operating at exact Raman resonance. We demonstrate that the CARS mechanism actually comprises two opposite and competing interactions, which respectively create and annihilate phonons in the Raman medium. Furthermore, we show that both the phase mismatch of the CARS four-wave mixing process and the level of pump depletion determine which of these two interactions takes place along the converter path length. In addition, we demonstrate that our CARS model is fully in line with seemingly contradictory findings in Raman conversion experiments. Finally, we discuss the fundamental differences between our CARS interpretation and the CARS models presented earlier.      

交叉蝴蝶结纳米结构的Fano共振效应用于表面增强相干反斯托克斯拉曼散射的理论研究

Fano共振效应拥有独特的局域场增强效果,在表面增强相干反斯托克斯拉曼散射中,不同波长局域场增强空间位置相同的结构结合Fano共振效应,可以实现混合频率共振模式,使得表面增强相干反斯托克斯拉曼散射总的增强因子得到大幅度提高。采用FDTD软件系统研究了对称的交叉蝴蝶结Au纳米结构的Fano共振效应,该效应使得交叉蝴蝶结结构中心位置附近的电场强度得到大幅度的增强,把该结构应用到表面增强相干反斯托克斯拉曼散射中,可以使表面增强相干反斯托克斯拉曼散射信号的增强因子高达1013,达到单分子检测的水平。     

基于Inagaki模式方法分析导体内谐振特性

当应用电场积分方程或磁场积分方程对导体散射特性进行矩量法分析时,在某些离散的频率点即内谐振点上,常常出现解的不稳定或不唯一情况。为了解决这一问题,该文提出了一种新型的消除内谐振的方法。这种方法基于电场积分方程,利用Inagaki模性质有效地去除了谐振模式,获得内谐振条件下正确的导体散射特性。该方法具有概念清晰和计算简便等优点。计算结果与公开发表的文献结果以及解析解相比,一致性良好。     

Enhanced and stimulated multiphoton processes in free atoms

An enhanced two-photon emission has been observed between the 6S and the 4S levels of potassium. The priming field is the stimulated electronic Raman emission at 2720 cm^-1due to scattering of ruby laser radiation from the4P_{3/2}state in potassium. The intense emission at the complementary frequency ω2is close to the 5P → 4S resonance lines. As a result, the coupling coefficient has a resonance character that is favorable for the enhancement. The observed results are compared with a simple analysis. The relation of the enhanced emission with two-quantum absorption, stimulated Raman effect, and parametric four-photon processes is discussed.     

Reflection of pulses in a nonlinear random medium with strong fluctuations

The reflection of delta pulses from a strongly fluctuating nonlinear random medium is studied. With the use of the equation of a backscattered field obtained by the invariant imbedding method, a numerical algorithm is developed for solving the one-dimensional direct and inverse problems of wave reflection in time representation. The solutions obtained can be used for investigation of the fluctuation-related features of reflections occurring in nonlinear random media and in the design of remote sensing methods. The conditions that give rise to wave stochastic resonance and dynamic effects in nonlinear random reflections are considered.     

自组装法制备团簇Ag纳米结构衬底及其SERS

采用自组装方法,在3-Aminopropyltrimethoxy silane(APS)分子修饰后的玻璃衬底表面,获得了二维Ag纳 米结构衬底。在波长为532nm激光激发下,研究了沉积在衬底表面的 Rhodamine 6G(Rh6G)分子的拉曼光谱特性。结 果表明,制备的二维Ag纳米结构衬底具有强的拉曼增强特性,增强因子可以达到 10⁷ 倍。这说明,在外光场作用下,制备的Ag纳米结构衬底表面能够形成的强局部电磁场分布, 可以有效提升探针分子的光谱辐射效率,从而获得高增强拉曼散射。     

Kerr效应对耦合双原子与压缩真空场Raman相互作用系统中光场量子特性的影响

研究了存在Kerr介质时，耦合双原子与单模压缩真空场Raman相互作用系统中光场的量子特性，讨论了Kerr介质与光场的耦合强度对光场量子特性的影响。