Single-optical-element soft-x-ray interferometry with a laser-plasma x-ray source

We report on a compact interferometer for the water-window soft-x-ray range that is suitable for operation with laser-plasma sources. The interferometer consists of a single diffractive optical element that focuses impinging x rays to two focal spots. The light from these two secondary sources forms the interference pattern. The interferometer was operated with a liquid-nitrogen jet laser-plasma source at lambda=2.88 nm. Scalar wave-field propagation was used to simulate the interference pattern, showing good correspondence between theoretical and experimental results. The diffractive optical element can simultaneously be used as an imaging optic, and we demonstrate soft-x-ray microscopy with interferometric contrast enhancement of a phase object.     

Measurement Accuracy in Phase-Shifting Point Diffraction Interferometer with Two Optical Fibers

A phase-shifting point diffraction interferometer (PS/PDI) with point sources of two single mode optical fibers has been developed, which will be appropriate for the surface figure measurement of large aperture optics on a sub-nanometer scale. To reduce the measurement error factors, a fiber optic plate (FOP) is used as a projection plane for interference pattern. Errors caused by imperfection of optical alignment, such as position of point sources and tilt of FOP, are minimized by analyzing the measured phase data with an original method. Measurement accuracy in the PS/ PDI is estimated with the interference pattern produced by the two optical fiber sources. If inhomogeneity of the FOP and a systematic error of the PS/PDI are eliminated, the measurement accuracy of the present system is estimated to be less than 4nm P-V and 0.7nm rms, respectively, at a measurement wavelength of 632.8 nm.     

Generation of a variable linear array of phase-coherent supercontinuum sources

We investigate the coherence properties of a linear array of white-light sources produced in bulk media by ultrashort laser pulses. The array is generated out of the spatial interference pattern between two laser pump pulses, so that the number of supercontinuum sources and their separations can be easily manipulated by varying the geometry of the laser beam interaction. We find that all the secondary white-light sources which arise from the generation of filaments in the optical medium are well phase-locked and are thus able to generate stable and high-visibility multiple-beam interference patterns in the far-field. Observations are compared to the results of a simple model which takes into account a clamping of the peak laser intensity inside the filaments and includes intensity-dependent phase shifts among the different sources. PACS 42.65.Jx; 42.65.Ky; 42.65.Re     

Real time phase modulation measurements in liquid crystals

We propose real time phase measurements in liquid crystals cells using Young's interferometer constructed with a new principle with possibility to control the distance between two point sources. The optical interference optical pattern is detected by a bicell photo-detector in a back Fourier focal plane. A phase modulation controlled by a monopixel liquid crystals’ cell placed in a reference arm of interferometer is observed as a dynamic shift of the fringes’ pattern in spatial domain. Concept of signals’ demodulation in the Fourier focal plane will be described using a new approach to the demodulation signals. In this work we evaluate the demodulation condition of our setup and we present measurements of a dynamic phase response for nematic liquid crystals and antiferroelectric liquid crystals cells.     

CCD采集Twyman-Green干涉图中非正常条纹的探究

 CCD采集Twyman Green干涉图时常出现异常干涉条纹,阻碍观察者对真实条纹的判断与精确测量。针对此种现象,基于莫尔条纹的形成机理和CCD的空间结构,从理论上分析此非正常条纹为等厚干涉条纹与CCD空间结构形成的莫尔条纹。通过对光场分布的计算和Matlab数值模拟,调整各参数,重现此种条纹,进一步验证了理论解释的正确性。莫尔条纹对精细干涉条纹的观察有妨碍作用,实验中应当避免使用分辨率相当的CCD进行采集,或可通过改变CCD探测器的采样算法,使莫尔条纹效应减弱甚至消失。     

一维光晶格中玻色凝聚气体的干涉

对捕限在三维轴对称谐振势阱叠加一维光晶格的组合势中的玻色凝聚气体，文章基于平均场G-P方程并运用传播子方法，求解玻色凝聚气体基态波函数及其随时间的演化，给出了物质波干涉图样的空间分布与光晶格势周期结构之间的关系.研究表明，运用这一方法得到的光晶格势中物质波干涉条纹与光学中的多光束干涉相类似，并且与Andrews 和Peil等人的实验结果一致.物质波干涉图样随时间的演化也与Sadhan K. Adhikari通过直接数值求解G-P方程所得结果基本相同. 关键词： 玻色凝聚气体 子凝聚原子云 光晶格势 干涉     

Novel Design of Sagnac Interferometry Assisted with Surface Plasmon Resonance Based Sensor Technique

In this work, we demonstrate a novel design to investigate interfacial reaction of optical activity materials, utilizing a Sagnac interferometer assisted with surface plasmon resonance based sensor technique. Upon application to interrogate optical activity, the type-2 optical configuration of close loop in this work can entirely encircle the interaction zone of surface plasmon resonance reacting with optical activity medium, while the type-1 optical configuration of close loop does partially. The greater the geometrical phase owing to the encircled interaction zone between optical activity medium and polarized light, the larger the phase shift of interference pattern modulated by the concentration of optical activity medium. The slope of phase shift in interference phase pattern of p-wave vs. concentration of dextrose solution determined with this method is greatly improved, 3000 times better than that with Lee's method, 18,600 times with Lin's method, and 222,000 times with Chou's method. Besides, the pinch point of phase shift vs. concentration indicates the ending of interference pattern phase shift as the concentration of each tested optical activity medium keeps climbing up, and can reflect the strong dependence of molecular shape during interfacial adsorption.     

实时全息术检测透明物的一种新方法

介绍了实时全息术检测透明物的一种新方法,它采用物光再现的参考光和参考光通过全息图的直透光所形成的干涉图纹检测透明物体的变化。证明了这组干涉图纹与用参考光再现的物光和物光通过全息图的直透光所形成的干涉图纹分布规律相似,仅在相位上相差π。还讨论了这组干涉图纹的衬比和获得最佳衬比的条件。此方法可消除物光光路上某些因素带来的相位畸变,避开待测物体自发光的干扰,并可在全息图后方任意位置进行记录,这使实时全息术在实践中更具有灵活性,有助于它在更广阔领域内的应用。     

A comparative study of spliced optical fibers

A fusion-spliced optical fiber is examined with a laser sheet of light. A CCD camera is used to record the transverse interference pattern from the fiber. The buckling on the fiber material in one direction of the spliced point is distinct inside the transverse interference pattern. The refractive index profile inside the fiber core, obtained at different illumination directions, is calculated using a new method showing the change in the refractive index due to fusion splicing of the fiber. A simple theoretical model is introduced to simulate the anomalous behavior in the transverse interference fringes due to a slight change of the optical parameters.     

二维光纤干涉理论

分析了由三根单模保偏光纤纤端出射光场的干涉特性,建立了二维光纤干涉的理论模型.在一级近似下,推导了二维光纤干涉光场场强分布的理论表达式.讨论了实现二维光纤干涉的相关条件,并用二维傅里叶变换方法,分析了干涉图的空间频谱特性.给出了相关实验结果.     

迈克耳孙干涉仪异常现象研究

观察并解释了迈克耳孙干涉仪的分光板被前后倒置后干涉条纹的变化，计算了这种异常情况下的光程差和干涉条纹形状的变化．     

Complete destructive interference of partially coherent sources of acoustic waves

Theoretical analysis has recently shown that the optical fields from several point sources may exhibit complete destructive interference even if the sources are not fully coherent with respect to each other. The experimental verification of this statement in the optical domain is not easy. In this Letter we demonstrate the effect using acoustical waves instead of light waves.     

Interference structure of the field of infrasonic directed sources in shallow water

The effect of the beam pattern of sources on the spatial interference structure of the infrasonic field in shallow water has been studied numerically. Calculations have been performed for a monopole and differently oriented dipoles and quadrupoles in the near-field zone, where the modes have not yet formed, as well as in the far-field zone, where the mode interference is observed. Dependence of the interference patterns at different frequencies on the emission and reception horizons, the multipole type, and the wave distance has been demonstrated. The importance of taking into account the horizontal beam pattern of sources in the far-field zone has been shown.     

光学实验的计算机仿真

基于计算机仿真技术,以光学干涉实验和滤波实验为研究对象,应用Matlab软件数值模拟了杨氏双缝干涉实验和多光束干涉实验干涉图形和光强分布图,数值模拟了光学滤波实验字母滤波后的频谱图和字母成像图,结果表明,计算机仿真结果能够清晰的表达出实验和理论的效果。研究结果为光学实验的课堂教学提供了参考。     

基于光干涉法的光学玻璃应力测量方法研究

以平板理论为基础,利用牛顿环应力变形导致干涉图样的微小变化,提出一种基于光干涉法测量玻璃体应力的无损测量方法。理论推导出牛顿环曲率半径与应力之间的变换关系,利用自行设计的可安装在牛顿环仪上的施压装置,实验研究了施加应力与干涉图样的变换关系,通过理论分析与实验比较,证明了用牛顿环干涉法测量应力的可行性。利用该装置及方法对光学玻璃试样的应力进行测量,测量结果与实际施加的应力进行比较,误差最小为0.8%。     

干涉法测量光学材料非线性折射率的方法研究

提出了一种基于楔形平板等厚干涉原理测量光学玻璃非线性折射率变化的方法。在理论分析的基础上,建立了变形的等厚干涉条纹变化△e／e与待测玻璃平片（K9玻璃）折射率变化量△nb之间的数学模型;在选取一定的实验条件下,获得等厚干涉实验测量干涉图样,并利用MATLAB对实验所得的干涉图进行图像数据处理分析计算,恢复出非线性变化光学玻璃材料的折射率变化量△nb该方法的测量精度可达10^-6。     

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.     

Quasi interference of perpendicularly polarized guided modes observed with a photon scanning tunneling microscope

The simultaneous detection of TE- as well as TM-polarized light with a photon scanning tunneling microscope leads to a quasi-interference pattern of these mutually perpendicular polarized fields. This interference pattern has been observed in the optical field distribution as a function of both position and wavelength. Comparison of experimental data with simulations confirms the interference of mutually orthogonal fields. This quasi interference is caused by conversion of the linearly polarized light of both modes into elliptically polarized light by a fiber probe.     

Observation of an optical vortex beam from a helical undulator in the XUV region

The observation of an optical vortex beam at 60 nm wavelength, produced as the second‐harmonic radiation from a helical undulator, is reported. The helical wavefront of the optical vortex beam was verified by measuring the interference pattern between the vortex beam from a helical undulator and a normal beam from another undulator. Although the interference patterns were slightly blurred owing to the relatively large electron beam emittance, it was possible to observe the interference features thanks to the helical wavefront of the vortex beam. The experimental results were well reproduced by simulation.     

光轴平行晶体表面时的锥光干涉图

针对光轴平行晶体表面时的锥光干涉图,提出了计算干涉场中振幅和相位分布的方法,据此绘制完整的干涉图,方便地显示出晶体参数改变时锥光干涉图的变化规律．用CCD摄像机拍摄了铌酸锂晶体的锥光干涉图,结果与理论完全一致。