非单色性光源对杨氏干涉条纹可见度的影响

光源的单色性影响其相干性. 任何实际的波列都有一定的谱线宽度, 谱线宽度表示了光源单色性的好 坏, 直接影响了干涉条纹的可见度. 对非单色性光源通过典型杨氏双缝干涉装置产生干涉条纹的理论进行分析和 仿真, 得出谱线宽度与干涉条纹的可见度的关系. 结论与实验相吻合. 其结果对于干涉法工程测量具有现实意义     

高斯光束照射下的等倾双光束干涉

根据等倾干涉原理，对高斯光束经薄膜反射后的光强、可见度、条纹分布进行了理论分析，讨论了入射角对光强、可见度分布的影响，相位角对条纹可见度的影响.数值模拟计算表明：沿着垂直于光传播方向的平面，反射光束叠加区域为一圆斑，随着入射角的增大，可见度逐渐减小，光强分布偏离了高斯分布，光斑变大，峰值减小.干涉条纹在空间的分布类似于平面波的薄膜等倾干涉，主要由入射角及薄膜厚度决定.     

多模液芯光纤干涉的实验研究

本文介绍了多模液芯光纤干涉的一些性质,干涉条纹的最大可见度条件.给出了干涉传感的二种测量结果.     

测量平板玻璃折射率实验中干涉条纹不清晰原因的探讨

分析了利用分光仪测量平板玻璃折射率中条纹不清晰的原因,借助数值模拟得出与实验观测相同的干涉光强分布,明确了平板玻璃的楔角是干涉条纹不清晰的主要原因.通过对比不同楔角下条纹可见度随平板玻璃反射率的变化关系,确定了平板玻璃的最佳反射率为0.5至0.7之间,使学生在实验中可以观察到清晰的干涉条纹.     

薄膜干涉条纹的可见度

在一级近似条件下，导出薄膜干涉条纹的可见度公式，人条纹可见度的角度定量分析干涉定域问题，直观地给出定域中心、定域深度随扩展光源、薄膜的劈尖角和厚度变化的规律．     

单色扩展光源杨氏双缝干涉可见度的理论模拟

杨氏双缝干涉实验中, 在理想单色扩展光源照射下, 干涉条纹的可见度不仅仅和光源宽度有关. 本文 理论模拟了理想单色扩展光源照射情况下光源宽度、 狭缝间距离等多项因素对干涉图样可见度的影响, 模拟结果 有助于学生对单色扩展光源干涉图样清晰程度的理解和掌握     

对白光干涉法测量透明介质折射率实验的探讨

在时域中求解得到,光路中存在色散介质的情况下,白光双光束干涉光强度.由此证明了:用白光干涉法测量得到的是白光在色散介质中的群折射率,而并非相关报道中认为的折射率;讨论了介质厚度及色散对于涉条纹的可见度和干涉条纹显现时动镜移动范围的影响.上述结论得到了实验验证.     

影响干涉条纹可见度的几个主要因素

影响干涉条纹可见度的几个主要因素潘留仙，徐勇（湖南益阳师专）（西南交通大学成都）两个或两个以上光波场在空间相遇后是否能产生干涉？干涉程度如何？通常最直观判别的办法就是考察它们相遇后有无干涉条纹和干涉条纹的清晰程度。由于干涉条纹的清晰程度直接反映了光波...     

钠光双线光谱下测量平板玻璃折射率实验的优化设计

利用分光仪测量平板玻璃折射率实验中,由于钠光双线光谱的影响,干涉场中往往得不到足够多清晰的干涉条纹,影响实验测量.借助数值计算分析出钠光双线光谱对透射光干涉场分布以及条纹可见度的影响,综合考虑理论结果和工艺要求,选取反射率为0.6、楔角1′左右的平板玻璃,在实验中观测到足够多清晰的干涉条纹,满足实验测量.     

计算机模拟分立双谱线光源的杨氏双缝干涉

对分立双谱线光源的杨氏双缝干涉进行模拟,求解出不同线型和线宽时干涉条纹的可见度曲线、光强分布曲线和干涉图样,用直观的计算机图形说明了分立双谱线的线型和线宽对干涉条纹的影响．     

Experimental interference of independent photons

Interference of photons emerging from independent sources is essential for modern quantum-information processing schemes, above all quantum repeaters and linear-optics quantum computers. We report an observation of nonclassical interference of two single photons originating from two independent, separated sources, which were actively synchronized with a rms timing jitter of 260 fs. The resulting (two-photon) interference visibility was (83+/-4)%.     

Coherence characteristics of light-emitting diodes

We report the measurement of coherence characteristics of light-emitting diodes (LEDs). Experiments were performed using red and green color LEDs directly illuminating the Young's double slit kept in the far-zone. Fourier transform fringe analysis technique was used for the measurement of the visibility of interference fringes from which the modulus of degree of spectral coherence was determined. Low degree of spectral coherence, typically 0.4 for red and 0.2 for green LED with double-slit separation of 400 μm was observed. A variable slit was then kept in front of the LEDs and the double slit was illuminated with the light coming out of the slit. Experiments were performed with various slit sizes and the visibility of the interference fringes was observed. It was found that visibility of the interference fringes changes drastically in presence of variable slit kept in front of LEDs and a high degree of spectral coherence, typically 0.85 for red and 0.8 for green LED with double-slit separation of 400 μm and rectangular slit opening of 500 μm was observed. The experimental results are compared with the theoretical counterparts. Coherence lengths of both the LEDs were also determined and it was obtained 5.8±2 and 24±4 μm for green and red LEDs, respectively.     

Influence of Decoherence on Interference Between Two Bose-Einstein Condensates

The influence of decoherence on interference between two trapped Bose-Einstein condensates with arbitrary initial states is studied. Analytic expressions of the intensity and visibility of the interference pattern are found. It is shown that the decoherence weakens the interference intensity and decreases the visibility of the interference pattern.     

Classical visibility limit for three-photon interference

It is shown theoretically and experimentally that the third-order interference of intensities, which is studied in many works performed in the last decade and is usually attributed to three-photon entanglement, can also be observed for classical light with a high visibility up to 81.8%. The calculations show that classical sources ensure an even higher visibility of the interference pattern up to 94.4% for fourth order intensity interference. Thus, a large visibility of the interference pattern of the third and higher orders cannot be considered an attribute of the nonclassical character of the effect.     

Ghost interference with partially coherent radiation

Ghost interference with partially coherent radiation sources is studied using optical coherence theory. The visibility of the ghost interference fringes is strongly influenced by the transverse size and transverse coherence width of the source. An increase of the transverse source size leads to a decrease of the fringes' visibility. An increase of the transverse coherence results in an increase of the visibility. The difference between ghost interference formed with entangled photon pairs and with partially coherent light is discussed.     

Third-order ghost interference with thermal light

A scheme for third-order ghost interference with thermal light is proposed. The visibility and resolution of the interference fringe related to the bandwidth of the spatial frequency spectrum of the source are analysed. The results show that the visibility of the third-order ghost interference fringe is much higher than that of the second-order one.     

Second-order temporal interference of two independent light beams at an asymmetrical beam splitter

The second-order temporal interference of classical and nonclassical light at an asymmetrical beam splitter is discussed based on two-photon interference in Feynman's path integral theory. The visibility of the second-order interference pattern is determined by the properties of the superposed light beams, the ratio between the intensities of these two light beams, and the reflectivity of the asymmetrical beam splitter. Some requirements about the asymmetrical beam splitter have to be satisfied in order to ensure that the visibility of the second-order interference pattern of nonclassical light beams exceeds the classical limit. The visibility of the second-order interference pattern of photons emitted by two independent single-photon sources is independent of the ratio between the intensities. These conclusions are important for the researches and applications in quantum optics and quantum information when an asymmetrical beam splitter is employed.     

Hong–Ou–Mandel interference with two independent weak coherent states

Recently,the Hong-Ou-Mandel(HOM) interference between two independent weak coherent pulses(WCPs) has been paid much attention due to the measurement-device-independent(MDI) quantum key distribution(QKD).Using classical wave theory,articles reported before show that the visibility of this kind of HOM-type interference is ≤ 50%.In this work,we analyze this kind of interference using quantum optics,which reveals more details compared to the wave theory.Analyses confirm the maximum visibility of 50%.And we conclude that the maximum visibility of 50%comes from the two single-photon states in WCPs,without considering the noise.In the experiment,we successfully approach the visibility of 50%by using WCPs splitting from the single pico-second laser source and phase scanning.Since this kind of HOM interference is immune to slow phase fluctuations,both the realized and proposed experiment designs can provide stable ways of high-resolution optical distance detection.     

Phase-locked laser coherent interference

A method of locking the relative phase to provide stable constructive or destructive interference between the phase-modulated sidebands from a pair of phase modulators is demonstrated. It is discussed theoretically for optimal fringe visibility related to the phase noise from faulty system. After phase locking using the phase modulating and lock-in technique,the drift of the relative phase is focalized around ±0.0016 rad and the fringe visibility is restricted to 2×10-4 .     

Line shapes of near-infrared DFB and VCSEL diode lasers under the influence of system back reflections

Laser diode line widths and line shapes are experimentally investigated in dependence on the diode current and on back reflections from an optical system. Four distributed-feedback (DFB)-type diode lasers and two vertical-cavity surface-emitting lasers (VCSELs) have been tested within the same optical setup and using the same fitting methods. System back reflection ratios of light reflected back to the laser have been varied between ?1?dB and ?45?dB and were below ?60?dB when all reflections were blocked. The background of this investigation is the evaluation of different laser types with respect to their suitability for sensor applications in which optical back reflections may occur, for example tunable diode-laser spectroscopy (TDLS). While DFB-type lasers showed almost pure Lorentzian line shapes and line widths of a few MHz, the tested VCSELs had a strong Gaussian contribution to the line shape, indicating stronger 1/f noise, which was also observed in the relative intensity noise of these particular lasers. System reflection ratios above ?25?dB had strong effects on the line width in both DFB diode lasers and VCSELs, while some influences have been observed at even lower reflection ratios for DFB diode lasers. As much smaller reflection ratios are typically required in TDLS systems to avoid etalon-like fringes and self-mixing interference effects, we conclude that the influence on the line width is not the most important reason to minimize back reflections in practical TDLS systems or to choose one type of diode laser over the other.