三能级钾原子气体三维傅里叶变换频谱的解析解

利用投影切片定理、傅里叶位移定理和误差函数给出三能级钾原子气体三维傅里叶变换频谱在T=0界面的解析解.固定均匀线宽,非均匀展宽和对角线相关系数可以定量地识别,通过在适当方向上拟合三维傅里叶变换频谱谱峰的切片来确定.结果表明,非均匀展宽增大,频谱图沿着对角线方向延伸,对角线相关系数增大,频谱图逐渐变圆,振幅也逐渐变小.     

Effect of the dispersion on multipartite continuous-variable entanglement in optical parametric amplifier

Based on the quantum fluctuations, we adopt the method of generalized V1 criterion to investigate multipartite entanglement characteristics in an optical parametric amplification system with the consideration of dispersion. The nonlinear interaction becomes strong because of the existence of dispersion coefficient σ. Considering the influence of dispersion factor σ, with increasing the pump parameter μ, the value of minimum variance V1 decreases and the squeezing curve nearly equals 1/(1 + μ). The larger particle number N results in a smaller variance and higher entanglement.     

Influence of pumping laser bandwidth on the quantum fluctuation chracteristic of non-degenerate optical parametric amplifier

Usually the quantum fluctuation characteristic of the non-degenerate optical parametric amplifier is analysed under the assumption of monochromatic pumping. However, in experiments, the driving beam with finite bandwidth is used to obtain the non-degenerate signal and idler beam amplifications. On account of that, we derive an analytical solution for the non-degenerate optical parametric amplification system with finite bandwidth laser pumping, and evaluate the associated quantum fluctuation. Finally, the application of the V₁ criterion to the bipartite entanglement is discussed.     

The high squeezing and entanglement in regular loss modulated optical parametric amplifier

We investigate the quantum fluctuation characteristic for time dependent regular loss modulated optical parametric amplifier for below and above threshold regions.It is found that a high squeezing and entanglement can be achieved.     

圆柱型光纤螺线圈轨道角动量模式

传统的沿z轴光纤传输光线的轨道角动量(orbital angular momentum,OAM)光束的制备方法共同之处都是从内部结构着想,光束的主光线基本上不变,只是波面在变.但要获得携带高mh的光有一定的难度.针对上述问题,本文建立以波面不变,光束主光线变化为基础的理论框架,利用微分几何理论验证不沿z轴圆柱型光纤螺线圈传输的光线可以携带高mh OAM的理论设想.研究发现:利用流动坐标(α,β,γ)计算光线在绕圆柱体的光纤中传输时光纤截面的衍射分布图呈现涡旋特征,有高阶OAM模式.当θ=θ0时,圆柱形轨道光纤过渡到直线轨道光纤.计算光线沿直线传输时光纤截面的衍射分布图是Airy斑,即圆孔衍射斑,无高阶OAM模式.     

位相不匹配情形Fokker-Planck方程的解及其在准位相匹配参量放大中的应用

在前文的基础上求得了简并参量放大系统在位相不匹配情况下的Fokker_Planck方程一个新 的解析解，然后通过准位相匹配(QPM)，计算振幅的量子起伏. 这一结果在不考虑损耗(k =0)情况下，与已知的按解Langevin方程求得的结果为一致. 对于一般的考虑损耗(k ≠0)情况，我们也得出损耗系数k对压缩态特性的影响. 关键词： 简并参量放大 位相不匹配的Fokker_Planck方程 准位相匹配技术(QPM技术)     

由非简并光学参量放大系统获得压缩态光所满足的Fokker-Planck方程及其解

通过解非简并光学参量放大的Fokker-Planck方程，得出压缩态光的腔内最大压缩的量子起伏为1/16（真空起伏为1/4）,与已知的简并光学参量放大情形腔内最大压缩为1/8相比，压缩度提高了一倍. 关键词： 非简并光学参量放大 Fokker-Planck方程 腔内最大压缩     

Einstein–Podolsky–Rosen entanglement in time-dependent broadband pumping frequency non-degenerate optical parametric amplifier

This paper investigates quantum fluctuations characteristic of time-dependent broadband pumping frequency non-degenerate optical parametric amplifier for below and above threshold regions. It finds that a high squeezing and entanglement can be achieved.     

Einstein——Podolsky——Rosen entanglement in time-dependent periodic pumping non-degenerate optical parametric amplifier

The solution of the time-dependent periodic pumping non-degenerate optical parametric amplifier (NOPA) is derived when the pump depletion is considered both above and below thresholds. Based on this solution, the quantum fluctuation calculated shows that a high entanglement and a good squeezing degree of the parametric light beams are achieved near and above thresholds. We adopt two kinds of pump fields: (i) a continuously modulated pump with a sinusoidal envelope; (ii) a sequence of laser pulses with Gaussian envelopes. We analyse the time evolution of continuous variable entanglement by analytical and numerical calculations, and show that the periodic driven pumping also improves the degree of entanglement. The squeezing and Einstein-Podolsky-Rosen (EPR) entanglement by using the two pumping driven functions are investigated from below to above the threshold regions, the tendencies are nearly the same, and the Gaussian driven function is superior to that of the sine driven function, when the maximum squeezing and the minimum variance of quantum fluctuation are considered. In the meantime, the generalization of frequency degenerate OPA to frequency non-degenerated OPA problem is investigated.     

The propagation characteristic of the EPR entanglement for a composite non-degenerate parametric optical amplification system

This paper applies the minimum variance V₁ criterion to monitor the evolution of signal and idler modes of a composite non-degenerate optical parametric amplification (NOPA) system. The analytics and numerical calculation show the influence of the transition time, the vacuum fluctuations, and the thermal noise level on the EPR entanglement of the composite NOPA system. It finds that the entanglement and the squeezing degrade as the minimum variance V₁ increases.