Competition between Quantum Interference and Stimulated Electronic Raman Scattering Processes via Hybrid Excitation in a Na2-Na System

An experimental observation of the competition between quantum interference and stimulated electronic Raman scattering (SERS) via equal-frequency hybrid excitation and collision-aided radiative excitation in a Na2-Na system is reported for the first time.It is found that the SERS for 3P1/2,3/2-4P are suppressed and the optically pumped stimulated emission (OPSE) for 5S-4P are enhanced dramatically at a particular excitation wavelength where constructive quantum interference between two transitions 3P1/2-5S and 3P3/2-5S in atomic sodium takes place.A theoretical analysis based on the dressed-atom approach is carried out to explain the experimental results.     

液芯波导中受激动力学散射与受激拉曼散射的竞争

研究了液芯波导中受激拉曼散射和受激动力学散射的阈值随泵浦激光脉宽的变化，发现受激动力学散射的阈值随泵浦脉冲前沿增长率增大而下降。研究了受激动力学散射和受激拉曼散射的竞争，结果表明受激动力学散射可分解为两种成分，其中与瞬态泵浦功率密度增长率相关的成分在大于阈值的泵浦脉冲前沿处于竞争优势，与瞬态泵浦功率密度相关的成分在高泵浦功率密度处于竞争优势，并讨论了其相应的机制。     

受激拉曼散射中的二阶量子关联

利用全量子理论和多模受激拉曼散射模型，研究了拉曼放大中，考虑泵浦光耗散时，斯托克斯光和泵浦光二阶量子关联函数随相互作用距离变化的特性，在不计及色散的影响时，斯托克斯光和泵浦光的二阶量子关联函数的变化主要取决于输入斯托克斯光和泵浦光的光强比，在极限情况下，本文的计算结果与拉曼产生的计算结果和经典耦合波理论的计算结果相符合。     

p型掺杂Si/Ge量子点的电子拉曼散射(英文)

在本文中我们首次报道了p型掺杂的自组织Si/Ge量子点中空穴能级子带间的电子拉曼散射,此电子跃迁的能量为105meV。Si/Ge量子点Ge Ge模的共振拉曼散射表明此空穴能级间的电子拉曼散射与Γ点附近的E0(≈2.52eV)发生了共振,而E1的能量小于2.3eV.变温实验和偏振实验进一步证实了我们的指认。所有观测的实验数据与6 bandk·p能带结构理论的计算结果吻合得很好。     

啁啾激光脉冲受激拉曼散射理论和粒子模拟

从入射光波、散射光波和等离子体波的三波耦合方程出发,推导小带宽频率啁啾对拉曼散射的影响.得到频率啁啾对拉曼背向散射有抑制作用,且背向散射不依赖于啁啾符号;正(负)啁啾对拉曼前向散射有微弱的增强(减弱)的作用.最后采用1D3V粒子模拟程序观测了不同啁啾参数下的受激拉曼散射现象,得到与理论分析一致的结果.     

三倍频Nd∶YAG激光抽运氧气中的受激拉曼和布里渊散射

报道了三倍频脉冲Nd∶YAG激光(355 nm)在两种不同带宽模式下抽运氧气中受激拉曼散射(SRS)和受激布里渊散射(SBS)的实验研究。在宽带(约1 cm-1)抽运模式下,只测到了前向受激拉曼散射,而没有观察到后向散射,其一级和二级斯托克斯最大能量转换效率可达22%和8%。在窄带(约0.003 cm-1)模式下,前向、后向受激拉曼散射和受激布里渊散射都测量到了,但大部分抽运能量都转换到受激布里渊散射,其转换效率可达67%。测量了两种带宽模式下各散射组分在它们最佳转换时的波形;窄带情况下后向受激拉曼散射和受激布里渊散射的脉宽分别可压窄至1.5 ns和2.3 ns,不到抽运脉宽的三分之一,使得受激布里渊散射峰值功率可大大高于抽运功率。对氧气中前向、后向受激拉曼散射和受激布里渊散射之间的竞争进行了讨论。     

三倍频Nd:YAG激光抽运氧气中的受激拉曼和布里渊散射

报道了三倍频脉冲Nd：YAG激光（355nm）在两种不同带宽模式下抽运氧气中受激拉曼散射（SRS）和受激布里渊散射（SBS）的实验研究。在宽带（约1cm^-1）抽运模式下,只测到了前向受激拉曼散射,而没有观察到后向散射,其一级和二级斯托克斯最大能量转换效率可达22％和8％。在窄带（约0．003cm^-1）模式下,前向、后向受激拉曼散射和受激布里渊散射都测量到了,但大部分抽运能量都转换到受激布里渊散射,其转换效率可达67％。测量了两种带宽模式下各散射组分在它们最佳转换时的波形;窄带情况下后向受激拉曼散射和受激布里渊散射的脉宽分别可压窄至1．5ns和2．3ns,不到抽运脉宽的三分之一,使得受激布里渊散射峰值功率可大大高于抽运功率。对氧气中前向、后向受激拉曼散射和受激布里渊散射之间的竞争进行了讨论。     

Statistical Properties of Stimulated Raman Scattering in a Nonlinear Regime

Statistical properties of the Raman scattering of an intense step pulse are investigated by numerical solution of the equations of a semi-classical theory with assignment of a random Gaussian distribution of the initial polarization over the sample. The probability density functions of the intensity, energy, delay time, and width of a Stokes pulse and also of the position, height, and width of the spectral peaks of the first incidental Stokes component with the preservation of the phase memory of scattering centers are calculated. The influence of collisional dephasing on the fluctuation of these characteristics is considered.     

S波段光纤拉曼放大器中级联受激布里渊散射串扰的实验研究

研究了光纤激光器前向抽运的S波段分布式光纤拉曼放大器中级联的受激布里渊散射(SBS)串扰现象。用窄光谱带宽(<100MHz)的可调谐激光二极管作为信号源,通过S波段分布式光纤拉曼放大器,当被放大的信号功率超过单模光纤受激布里渊散射的阈值时,出现了前向受激布里渊散射,这是传导声波布里渊散射在光纤放大器中放大的现象。随着拉曼放大器抽运功率的提高,在斯托克斯区,出现了两阶受激布里渊散射线,在实验中观测到偶数阶的受激布里渊散射谱线功率大于奇数阶的布里渊一瑞利散射线。当进一步增加拉曼放大器的抽运功率,出现了前向级联的多阶受激布里渊散射现象,拉曼放大器的增益下降,被放大的信号功率转换为受激布里渊散射,噪声变大。受激布里渊散射的串扰破坏了拉曼放大器的特性,使拉曼放大器无法在密集波分复用光纤传输系统中使用,因此需要严格地控制入纤的信号功率和放大器的抽运功率。在实验中还观测到在光纤拉曼放大器中被放大的信号光和受激布里渊散射线两侧的伴线。     

Analytical Model of Non-dispersion-limited Transient Stimulated Raman Scattering in Single-mode Silica Fiber in WDM Optical Communication System

1 IntroductionNowadays, fused silica fiber still is the most common fiber in wavelength divisionmultipleeing (WDM) OPtical commwhcation syStem. In the WDM system, themodulation type of input signal in one channel differs from another channel. FOrinstance, in the Ralnan fiber amplifiers, the pUmP is a continuous wave (CW) whilethe signals are pulse modulated. SO, when we study the SRS effect in the system, wemust take into account the different modulation type of signals. For a tWO-cha…     

Analytical Model of Non-dispersion-limited Transient Stimulated Raman Scattering in Single-mode Silica Fiber in WDM Optical Communication System

The non-dispersion-limited analytic solutions of unidirectional N-channel transient stimulated Raman scattering (SRS) coupling wave equation which governing the propagation of the optical signals in single-mode (SM) silica fiber have been presented. Taking into account the SRS cross coupling among the N-channels, the analytic solutions are applicable to the system with arbitrary channel separation and input signal light power.     

Effect of Stimulated Raman Scattering on Spectral Characteristics of Ultranarrow Pulses in a Mode-Locked Solid-State Laser

On the basis of numerical modeling, it is shown that the effect of the higher-order group-velocity dispersion is unable to account for the noticeable Stokes displacement of the generation spectrum in a LiSGaF laser with mode-locking due to self-focusing. The results of calculations indicate the determining influence of stimulated Raman scattering on the spectral characteristics of femtosecond pulses.     

单纵模Nd:YAG激光抽运CH4中强后向受激拉曼散射

用单纵模Nd:YAG二倍频激光[波长532 nm,线宽△vp＜100 MHz,脉宽(半峰全宽)6.5 ns]抽运CH4气体,观察到很强的后向一级斯托克斯(BS1)受激拉曼散射,这与前人采用脉宽30 ns的单纵模抽运激光得到的绝大部分为后向受激布里渊散射(SBS)完全不同,其原因是脉宽6.5 ns与本实验条件下CH4的受激布里渊散射声子寿命接近,受激布里渊散射处于瞬态.理论计算表明,这时的受激布里渊散射瞬态增益系数已略小于后向一级斯托克斯的增益系数,而被其竞争抑制.当脉冲重复频率为2 Hz,抽运能量为95 mJ时,在1.1 MPa CH4中,后向一级斯托克斯的量子转换效率高达73%,其时间波形出现张弛振荡,脉宽被压窄到1.2 ns,从而使后向一级斯托克斯峰值功率达到了抽运激光功率的2.7倍,而且其光束质量要大大优于抽运激光的光束质量.用编制的准二维计算机模型程序相当好地再现了实验中后向一级斯托克斯的时间波形张弛振荡.     

单纵模Nd:YAG激光泵浦H2气中的受激喇曼散射

用单纵模Nd:YAG激光(波长1.06μm,脉宽9ns,线宽0.003cm-1)泵浦氢气中的受激喇曼散射,产生很强的后向一级斯托克斯.当泵浦能量为120mJ,压力为1.5MPaH2时,后向和前向喇曼的光子转化效率分别为66%和15%,而在4MPa时两个数值分别为46%和39%.由于后向喇曼与前向喇曼和泵浦光的传播方向相反,二者的相互竞争产生了张弛振荡,使得后向和前向喇曼的时间波形都分裂为两个峰,后向喇曼的两个峰都被压窄到1ns,使峰值功率达到了泵浦光功率的二倍,这在前向喇曼是不可能的.而且后向喇曼的光束质量要大大优于泵浦光和前向喇曼的光束质量,在4MPaH2和脉冲重复频率为10Hz时,喇曼过程的放热使前向喇曼的光束质量变坏,但对后向喇曼的光束质量影响不大.计算表明,该实验条件下受激喇曼过程没有达到稳态,所有实验结果都可以而且只能用相关的瞬态受激喇曼理论解释.     

单纵模Nd∶YAG激光抽运CH_4中强后向受激拉曼散射

用单纵模Nd∶YAG二倍频激光[波长532 nm,线宽Δνp<100 MHz,脉宽(半峰全宽)6.5 ns]抽运CH4气体,观察到很强的后向一级斯托克斯(BS1)受激拉曼散射,这与前人采用脉宽30 ns的单纵模抽运激光得到的绝大部分为后向受激布里渊散射(SBS)完全不同,其原因是脉宽6.5 ns与本实验条件下CH4的受激布里渊散射声子寿命接近,受激布里渊散射处于瞬态。理论计算表明,这时的受激布里渊散射瞬态增益系数已略小于后向一级斯托克斯的增益系数,而被其竞争抑制。当脉冲重复频率为2 Hz,抽运能量为95 mJ时,在1.1 MPa CH4中,后向一级斯托克斯的量子转换效率高达73%,其时间波形出现张弛振荡,脉宽被压窄到1.2 ns,从而使后向一级斯托克斯峰值功率达到了抽运激光功率的2.7倍,而且其光束质量要大大优于抽运激光的光束质量。用编制的准二维计算机模型程序相当好地再现了实验中后向一级斯托克斯的时间波形张弛振荡。     

调Q倍频Nd：YAG激光泵浦氧气和氧－氦混合气体的受激拉曼散射

报道了调Ｑ倍频Ｎｄ：ＹＡＧ激光泵浦的高压工业用氧气和氧－氦混合气体的受激拉曼散射特性，研究了一阶、二阶斯托克斯（Ｓｔｏｋｅｓ）光的能量转换效率与泵浦光的能量及气压的关系，并探讨了如何抑制氧气的二阶斯托克斯的产生等问题。     

外部荧光种子植入法增强液芯光纤中CS2的受激拉曼散射研究

本文报道了运用外部荧光种子(罗丹明6G乙醇溶液)植入法对液芯光纤中CS2受激拉曼散射的增强研究。实验结果表明, CS2的二阶、三阶Stokes波分别获得了1.92和11.71倍的增益。并对外部荧光种子植入法增强液芯光纤中受激拉曼散射的机制进行了分析。     

Collisional Quantum Interference on Rotational Energy Transfer： Relation Between Integral Interference Angle and Rotational Quantum Number in Na2（A^1∑u^＋,ν=8～b^3∏0u,ν=14）-Na System

Collisional quantum interference （CQI） on rotational energy transfer was observed in Na2（A^1∑u^＋,ν=8～b^3∏0u,ν=14） system in collision with Na [Chem. Phys. Lett. 318 （2000） 107], and the degree of the interference was measured. The integral interference angle was obtaJned through theoretical calculation. We will research the factors that have effect on collisional quantum interference on rotational energy transfer in Na2（A^1∑u^＋,ν=8～b^3∏0u,ν=14）-Na system. Basing on the time-dependent first order Born approximation, and taking into account the anlsotroplc Lennard Jones interaction potentials and ＂straight-line＂ trajectory approximation, we obtain the factors that have effect on CQI in Na2-Na system, and obtain the relation between the integral interference angle and rotational quantum number.     

高功率纳秒光脉冲在单模光纤中的受激喇曼散射及抑制研究

利用包含喇曼增益、抽运消耗、自相位调制、交叉相位调制和群速度色散效应的耦合非线性薛定谔方程组,对千瓦级高功率纳秒脉冲在单模光纤中的传输特性进行了模拟计算.分析了输入脉冲和斯托克斯脉冲的演化过程,研究了大模面积光纤对受激喇曼散射的抑制作用.研究结果表明,采用模面积为530 μm~2的光子晶体光纤作为惯性约束聚变脉冲整形系统的传输介质,能有效抑制受激拉曼散射,不但信号衰减较小,而且中心凹陷程度较低.     

Stimulated Raman conversion of radiation from a YAG:Nd laser with wavelengths of 1.319, 1.338, and 1.357 µm in a barium nitrate crystal

We have studied stimulated Raman (SRS) conversion to the first Stokes component of multimode (M₂ = 8) radiation from a YAG:Nd laser with lasing wavelengths of 1.319 μm, 1.338 μm, and 1.357 μm in a barium nitrate crystal. We have obtained pulses of converted radiation with energies up to 120 mJ. We have achieved conversion efficiencies greater than 40% for each of the three Raman laser wavelengths of 1.530 μm, 1.556 μm, and 1.582 μm with divergence of the beams of converted radiation close to the diffraction-limited value (M₂ < 1.5). __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 3, pp. 330–334, May–June, 2006.