光学稳态简并四波混频

对特定介质中的光学稳态简并四波混频过程进行了数学描述,并对四波混频耦合波方程组作了数学推导,指出四波混频中有关参量之间的关系和特性。     

利用简并四波混频系统通过畸变介质传输图象研究

本文在研究光折晶体多波混频的基础上,从理论和实验上提出了利用简并四波混频系统单次通过畸变介质传输图象的方法,文末并给出了初步的实验结果。     

简并四波混频与位相复共轭(Ⅱ)

四、简并四波混频的理论研究工作 多年来,围绕简并四波混频的物理机制及影响位相复共轭反射波产生的效率的各种因素,开展了许多理论研究.这里只能作一概要的介绍.1.透明介质的简并四波混频理论 理论分析最初由Yariv等人完成.在图9中,与非线性介质相互作用的有四个波,即抽运光波Ef和Eb,探测光波Ep和共轭反射波Ec.假定它们均近似表示为平面波 一般在实验中探测光波及其共轭反射波相对抽运光波都弱得多,因此可以假定在混频相互作用中抽运光强度不变.现集中研究Ep和Ec的变化.由于四波耦合的结果,产生了波矢分别为Kc及Kp的三阶非线性极化利用…     

在等离子体中的简并四波混频——应用于等离子体诊断

所谓简并四波混频[1-3],是指频率相同的二束共线而相反方向传播的激光(第1,2光束)与另一束方向任意而频率相同的探测光(第3束),在具有三级极化率的介质中混频,从而产生频率相同的信号波(第4光束)。它与探测波共线而传播方向相反和相位互为共轭.如图1所示.简并四波混频在实时信息处理和象差补偿等的潜在的实用价值,使许多研究工作者在固体、液晶、金属蒸气和染料等各类介质中进行了广泛的研究[1-8]。 最近,Steel,Lam[9]和作者[10]首先计算了在等离子体中简并和二重简并四波混频的三级非线性极化率,并指出从红外至微波整个波段,等离子体是简…     

有机染料溶液中简并的四波混频和位相复共轭研究

本文研究了近共振增强的四能级系统有机染料溶液中简并的四波混频后向波和前向波的位相复共轭特性。用有效长度为5毫米、浓度为2.5×10^-5克分子的叶绿素A甲醇溶液作介质,当调QNd:YAG倍频抽运光能量为8毫焦耳时,非线性反射率为22％。研究了若丹明6G酒精溶液双光子共振增强的简并的四波混频作用。测量了非线性反射率与介质浓度及抽运波和物波强度的关系曲线。理论分析了四波混频前向波的位相复共轭特性,实验证实了理论的预言。另外,把四重简并的四波混频推广到二重简并。用9740有机染料二氯乙烷饱和吸收溶液作介质,实现了1.06微米到5320埃的象转换。介质长度为5毫米,抽运光能量为5毫焦耳时,转换效率达25％。理论分析表明,用对红外近共振吸收而对可见辐射是透明的介质可实现高效率红外象转换。 关键词：     

等离子体四波混频精确解透射光栅位形

给出等离子体介质中的简并与近简并四波混频形成透射光栅时的普适四波非线性耦合方程组。得到了在任意复耦合系数下的精确解析解，其解不仅适用于各种等离子体形态，也可以推广到光致折射材料中去。对进一步理论研究四波混频相位共轭原理以及研制新型非线性光学器件有所帮助。     

近简并四波混频相位共轭介质中的光强分布

从求解耦合波方程出发，详细研究了非线性光学介质中由近简并四波混频所产生的相位共轭过程。以上述波方程的解为基础，给出作为混频结果的反射传播相位共轭波沿介质轴向的光强分布，得到比以往文献中所报道的更为精确的结果，从而为选择工作物质的最佳尺寸提供了理论依据。     

后向波参量振荡中的受激散射竞争效应

本文对在强泵浦条件下的简并四波混频及其后向波参量振荡特性作了理论分析。考虑受激喇曼散射的竞争效应,求得了简并四波混频后向波参量振荡信号强度与泵浦输入强度的关系。对硝基苯介质的理论结果与实验结果基本符合。理论分析还指出,由于存在与泵浦强度有关的衰减系数,使参量振荡信号强度与泵浦强度呈多值关系。 关键词：     

等离子体四波混频透射放大理论

研究了寻常波在磁化等离子体中四波混频透射放大理论，得到了简并和非简并时的精确解析解，其结果适用于非磁化等离子体中的电磁波四波混频． 关键词：     

等离子体四波混频精确解——透射光栅位形

给出等离子体介质中的简并与近简并四波混频形成透射光栅时的普适四波非线性耦合方程组。得到了在任意复耦合系数下的精确解析解，其解不仅适用于各种等离子体形态，也可以推广到光致折射材料中去。对进一步理论研究四波混频相位共轭原理以及研制新型非线性光学器件有所帮助。 关键词：     

Highly efficient four-wave mixing induced by quantum constructive interference in rubidium vapour

We demonstrate efficient four-wave mixing with an intensity conversion efficiency of nearly 100% in theory without considering the Doppler-broadening effect in a four-level double-Λ system of hot ⁸⁷Rb gas. The corresponding experimental value of about 73% was reported in our earlier work under the same conditions. This dramatic efficiency is critically dependent on the constructive interference between two four-wave mixing processes relevant to the internally generated four-wave mixing signal.     

Single 10-fs deep-ultraviolet pulses generated by broadband four-wave mixing and high-order dispersion compensation

Broadband chirped-pulse four-wave mixing and a pulse compressor consisting of a prism pair and a grating pair are used to generate 10.3-fs deep-ultraviolet pulses. A large proportion of the dispersion up to 1000 fs² is compensated without inducing third-order dispersion, which together with the smooth spectral and temporal profiles of the pulses makes them suitable for ultrafast spectroscopy. Unexpected spectral narrowing is observed when short input pulses were used for four-wave mixing. This narrowing is explained in terms of other third-order nonlinear phenomena, namely self-phase and cross-phase modulations, which occur simultaneously with four-wave mixing.     

简并四波混频中的能级交叉效应

我们用微扰方法计算了近简并准二能级系统的三阶非线性极化率x⁽³⁾(-ω;ω,ω,-ω)。研究了简并四波混频的能级交叉效应,并与共振荧光的能级交叉效应比较。指出简并四波混频的能级交叉效应可用来测量上能级及下能级的弛豫速率。 关键词：     

Thermal loss mechanism in the generation of multifrequency laser emission via stimulated Raman scattering and four-wave Raman mixing studied by photothermal refraction spectroscopy

The heat produced in conjunction with the processes of stimulated Raman scattering and four-wave Raman mixing in hydrogen was measured by photothermal refraction spectroscopy. Many vibrational, rotational, and vibrationally shifted rotational Raman lines are exclusively/simultaneously generated by changing the polarization of the laser beam and the hydrogen pressure. Thermal loss occurs predominantly from vibrational Raman scattering, which can be ascribed to a large Raman shift frequency of 4155 cm^-1 for the vibrational transition. In contrast to stimulated Raman scattering, little or no thermal loss is observable during the process of four-wave Raman mixing. Received: 12 April 1999 / Revised version: 12 July 1999 / Published online: 20 October 1999     

Generation of multi-color stimulated raman emission from two-color linearly or circularly polarized pump beams

A laser beam at two different frequencies separated by 587 cm^–1 is focused into pressurized hydrogen (rotational transition energy, 587 cm^–1) to generate multi-color stimulated Raman emission. The polarization state and the pulse energy are measured for each generated emission line using linearly and circularly polarized pump beams. The effect of the polarization is discussed by using a parameter characterizing the polarizability of hydrogen and a conservation rule for the angular momentum in four-wave mixing. Many rotational lines are generated with linearly polarized pump beams through a four-wave mixing process. This is in striking contrast to the results obtained by using a single-color circularly polarized pump beam which generates only one rotational line through a conventional stimulated Raman process.     

Coexisting four-wave mixing and six-wave mixing in three-level atomic system

We demonstrate the coexisting four-wave mixing (FWM) signal and six-wave mixing (SWM) signal which can be enhanced both by electromagnetically induced transparency (EIT) and optical pumping effect in a common three-level and open four-level inverted-Y type systems of ⁸⁵Rb. We also analyze the effect of optical pumping in different energy level systems by arranging laser beams and comparing the strength of the increased and reduced absorption caused by optical pumping.     

Degenarate four-wave mixing in LiNbO3 and LiTaO3

Continuous wave generation of complex conjugate wavefront via four-wave mixing in LiNbO₃ and LiTaO₃ with diffusion non-linearity is studied. Strong anisotropy of the degenarate four-wave mixing is observed and explained.     

汞蒸汽中利用四波和频产生125nm附近可调谐真空紫外激光

以氩为匹配气体的汞蒸汽四波和频实验中,一束泵浦光(ω₁)与汞原子6¹S₀—7¹S₀严格双光子共振,当另一束泵浦光(ω₃)在汞原子7¹S₀—9¹P₁跃迁的蓝端调频时,产生可调谐的真空紫外(VUV)激光(ω₄=2ω₁+ω₃),其 关键词：     

Four-Wave Mixing in Microwires to All-Optical Signal Processing in Mode-Division Multiplexing Systems

Abstract

Mode-division multiplexing requires all-optical signal processing techniques that are able to deal with a new coding dimension, the spatial mode. In this context, optical microwires emerge as a potential highly non-linear and multi-modal waveguide envisioning the development of all-optical signal processing devices to mode-division multiplexing systems based on the four-wave mixing process. The inter- and intramodal phase-matching conditions for the four-wave mixing process are mapped as a function of the microwire diameter and the wavelength of signals. Moreover, the efficiency of four-wave mixing considering a strong guiding regime is investigated in the multi-modal regime.     

Nonlinear emission in sodium vapour upon pulsed-laser excitation of the 42 P levels

Parametric four-wave mixing, stimulated electronic Raman scattering and amplified spontaneous emission cascades have been studied experimentally by single-photon resonant and near-resonant excitation of the 4² P levels of dense sodium vapour. The dependence of emission intensities on laser detuning and exciting laser power is discussed.