基于四波混频过程的纠缠光放大

双模纠缠态是量子信息领域一种重要的量子资源,本文基于四波混频过程从理论上提出了对双模纠缠态的单个模式(单模放大方案)和对双模纠缠态的两个模式(双模放大方案)的放大.利用光学分束器模型来模拟在光学传输过程中损耗引入的真空场噪声,利用部分转置正定判据分析了两种不同的放大方案中四波混频过程的增益对初始双模纠缠态的纠缠程度的影响.结果表明,在特定的损耗情况下,两个方案中初始双模纠缠态的纠缠度都随增益的增大而减小,直至消失,且双模放大方案中初始双模纠缠态纠缠消失得比单模放大方案中更快.本文的理论结果为实验上实现基于四波混频过程的双模纠缠态的放大奠定了理论基础.     

原子气室中四波混频线型的实验研究

理论上利用双边费曼图对四波混频过程进行了研究,该方法可直观清晰地展示光与原子相互作用的物理过程。计算了四波混频过程的色散性质。实验上研究了85 Rb原子D2线的四波混频线型,并且对实验结果进行了拟合,两者符合较好。对四波混频线型的研究可加深对四波混频过程的理解,从而促进四波混频过程在量子信息研究中的应用。     

铷原子中参量六波混频和量子拍的研究

在铷原子中实现了轴向相位匹配的参量六波混频,并探测到位于红外光谱区的六波混频信号.六波混频信号与泵浦激光进行和频,产生了位于可见光范围内的可调谐的和频信号,并从和频信号中观察到频率为608 cm 1的量子拍.结果表明,六波混频信号中的量子拍能够用于研究原子和分子的相干特性.     

光学相位共轭与四波混频

回顾并论述了光学相位共轭及四波混频技术的发展过程，介绍了四波混频相位共轭的原理、相关的介质材料、应用前景及技术发展趋势。     

超短脉冲简并四波混频时间分辨研究

研究了简并以混频的时间分辨曲线，数值模拟了由延迟时间引起的两种不同光栅的时间分辨曲线以及曲线的约化半宽度与约化弛豫时间ｔｒ／ｔｐ的变化关系。     

微结构光纤次芯中的四波混频过程

利用Ti:sapphire飞秒激光脉冲在微结构光纤包层的次芯中通过参量四波混频效应获得480—550nm的反斯托克斯波,转换效率可高达28%. 通过改变输入光的偏振方向可以调节反斯托克斯波的中心波长. 理论模拟了飞秒激光在次芯中的模式特性和色散特性,较好地解释了实验结果. 关键词： 微结构光纤 飞秒激光脉冲 参量四波混频过程     

简并四波混频相位共轭介质中的光强分布

相位共轭现象在很多领域有着广阔的应用前景。本文对非线性介质中所发生的简并四波混频相位共轭过程进行了较详细的分析，以耦合波动方程的解为基础，研究了介质中正向探测波和反向相位共轭波的光强分布，得到比迄今文献报导的更为确切的结果。     

基于级联四波混频过程的量子导引

多组份量子导引是一种重要的量子资源,是安全量子通信网络的基础.本文设计了串联级联四波混频和混合级联四波混频两种不同的方案,并基于这两种方案分别产生了三组份量子导引和五组份量子导引,通过构建系统量子态的协方差矩阵,理论研究了两种方案产生不同模式组合间的导引参数随四波混频过程振幅增益的变化.结果表明,利用这两种方案可以实现...     

Linear and nonlinear optical properties of semiconductor particles

Abstract

The field of nonlinear optics is briefly introduced, followed by a review of quantum size effects in small semiconductor particles, with special reference to the linear and nonlinear optical properties. Experimental methods, especially the “laser induced grating” technique are described. Semiconductor (CdS _x Se_1?x ) doped glasses are examined, both the commercially available niters and a specially made experimental CdSe doped glass. Both linear and nonlinear optical properties are discussed. Colloidal and polymers systems are also briefly discussed.     

Evolution of first-order sidebands from multiple FWM processes in HiBi optical fibers

The generation of two idler waves inside a high birefringent (HiBi) optical fiber through three four-wave mixing (FWM) processes is studied theoretically. The coupled-equations for the field amplitudes are derived and analytically solved, in the co-polarized and orthogonal polarization schemes. The obtained solutions take into account the delayed Raman response of the medium. The polarization sensitivity of the generation of the idler waves is analyzed. Results show that the stimulated Raman scattering does not change the efficiency of the idler wave generation in the co-polarized scheme, whereas in the orthogonal polarization scheme that nonlinear process decreases the efficiency of the four-wave mixing processes. Results also show that this set of multiple four-wave mixing processes is physically quite different from the typical single or dual pump four-wave mixing configurations. Findings show that the power transfer from the pumps to the idler fields can lead to a monotonous growth, or a periodic evolution of the sidebands along the fiber. Results show that the process efficiency varies greatly with the angle between the two pump polarizations.     

蒽二酮类化合物的合成及结构-非线性光学性能关系的研究

设计合成了6个新的蒽二酮类化合物,用紫外可见吸收光谱、傅里叶变换红外光谱、1H 核磁共振和元素分析表征了结构.采用飞秒激光,运用简并四波混频法,研究了化合物在非共振状态下的三阶非线性光学性能.它们的三阶非线性光学极化率χ(3)为2.62～3.55×10－13 esu,非线性折射率n2为4.82～6.52×10－12 esu,分子二阶超极化率γ为2.57～3.25×10－31 esu,响应时间τ为91～116 fs.探索了化合物的分子结构对三阶非线性光学性能的影响.增长共轭链,形成供吸供构型,增大取代基的供电子能力,提高共轭体系的共平面程度等因素有利于获得较大的三阶非线性光学性能.     

Role of topological phase-defects in the parametric generation process

We show that topological phase-defects are spontaneously generated from noise fluctuations in the degenerate configuration of the parametric interaction. These localized coherent structures are shown to affect the coherence properties of the parametrically generated field. It is shown that the emergence of coherence in the fundamental field relies on a previously unrecognized process of mutual annihilation of pairs of neighboring phase-defects. More precisely, the density of phase-defects N, and the time correlation τ_c of the generated field, are shown to exhibit a power-law behavior with the propagation length, i.e., .     

Generation and amplification of dual-color femtosecond pulses by a noncollinear optical parametric up-conversion process

Noncollinear optical parametric up-conversion generation and amplification are realized in a thick β-barium borate (BBO) crystal, and a couple of visible femtosecond up-conversion laser pulses can be achieved by a femtosecond pulse at 800 nm as the pump sources. The theoretical and experimental results indicate that there exist phase-matching conditions for dual-color noncollinear parametric up-conversion generation and amplification, and their wavelengths can be tuned by rotating the BBO crystal. This parametric up-conversion generation and amplification can be attributed to three and five-wave mixing in a thick BBO crystal, and it shows the potential application on optical parametric chirped pulse amplification (OPCPA) to generate multi-color ultraviolet or visible femtosecond laser pulses pumped directly by femtosecond fundamental laser pulses without frequency-doubling or tripling.     

Theoretical Analysis of the Polarization- and Frequency-Dependent Gain for Fiber Optical Parametric Amplifier

Abstract

We develop the gain expression of fiber optical parametric amplifier with birefringent effect and loss. The simulations show that the optical parametric amplifiers' gain is frequency-dependent and polarization-dependent. If the signal polarization state goes along the fast axis, when the average half-difference of two pump frequencies is smaller, the gain flatness is better; if the signal polarization state goes along the slow axis, when half-difference of two pump frequencies is smaller, the gain flatness is worse, and the gain bandwidth becomes wider. We still find that the signal gain is different under the distinct signal polarization state.     

Broadband second harmonic generation of an optical frequency comb produced by four-wave mixing in highly nonlinear fibers

We demonstrate broadband second harmonic generation of low-energy pulses produced by injecting two single-frequency lasers into a highly nonlinear fiber. Full nonlinear conversion of the corresponding spectra, consisting of broadband (∼200 nm) optical frequency combs at ∼1580 nm, were obtained by using conventional birefringence phase-matching in two BIBO crystals (2-mm and 100-μm long) with a normal incidence configuration. The crystals were not tilted and the pulses were not compressed. This broadband conversion results from the large phase-matching bandwidth of the nonlinear BIBO crystals at ∼1550 nm, but also seems to be a consequence of a fundamental comb with small spectral phase variation.     

基于小波变换的长距离光正交频分复用系统中四波混频引起的相位噪声分析

四波混频（FWM）效应是相干光正交频分复用（CO-OFDM）系统中最主要的非线性作用。分析基于小波变换的相干光正交频分（WT-OOFDM）系统原理,研究小波变换对FWM效应和光放大器自发辐射（ASE）引起的相位噪声的改善效果。数值结果表明,在采用常规G. 652光纤,100 Gbit/s的WT-OOFDM传输1500 km时,非线性相位噪声降低20%,总相位噪声降低15%。     

双光子过程耦合腔系统中光场的量子特性

本文研究了双光子过程原子与耦合腔相互作用系统中腔场的压缩效应和反聚束效应.考虑系统总激发数等于2的情况,利用数值计算方法讨论了腔场间的耦合强度变化和原子与腔场间耦合强度变化对反聚束效应的影响.研究结果表明:腔场不呈现出压缩效应;腔场的反聚束效应与原子与腔场的耦合系数之间,以及与腔场间的耦合系数之间都存在着非线性关系,