迭代最小二乘法用于非线性移相器的标定

针对移相干涉仪中移相器的非线性会影响测量结果准确性的问题,提出了一种基于迭代最小二乘拟合的标定干涉仪移相器的新方法。对移相器加电压并采集若干幅干涉图后,通过在帧间和帧内迭代开展最小二乘拟合可计算出干涉图间移相值,从而得出了电压值与移相值的对应关系曲线,通过对曲线作非线性拟合并对电压值进行精密调整,完成移相器的精确标定。在改造后的干涉仪上对此标定方法进行验证,与Zygo干涉仪相比,相同元件下两者测量结果之差的RMS值为1.726 nm。该标定方法可以降低高精度面形测量干涉仪对移相器线性度的要求。     

On Non-conservative Forces and Topological Quantum Phases

A generic non-conservative force, applied to an interferometer particle for a period in the past and then turned off, leaves stationary phase and fringe shifts in the now force-free interferometer. Both Aharonov-Bohm and Aharonov-Casher topological phase and fringe shifts can be created in this way. The specific sources of the non-conservative forces behind Aharonov-Bohm and Aharonov-Casher stationary fringe shifts are, respectively, Faraday induction fields and Maxwell displacement currents, now off.     

Inelastic effects in Aharonov-Bohm molecular interferometers

Inelastic effects arising from electron-phonon coupling in molecular Aharonov-Bohm (AB) interferometers are studied using the nonequilibrium Green's function method. Results for the magnetoconductance are compared for different values of the electron-phonon coupling strength. At low-bias voltages, the coupling to the phonons does not change the lifetime and leads mainly to scattering phase shifts of the conducting electrons. As a result of these dephasing processes, the magnetoconductance of the molecular AB interferometer becomes more sensitive to the threading magnetic flux as the electron-phonon coupling is increased, opposite to the behavior of an electric gate.     

Dispersion compensation for atom interferometry

A new technique for maintaining high contrast in an atom interferometer is used to measure large de Broglie wave phase shifts. Dependence of an interaction induced phase on the atoms' velocity is compensated by applying an engineered counterphase. The counterphase is equivalent to a rotation, is precisely determined by a frequency, and can be used to measure phase shifts due to interactions of unknown strength. Phase shifts of 150 rad (5 times larger than previously possible) have now been measured in an atom beam interferometer, and we suggest that this technique can enable comparisons of atomic polarizability with precision of one part in 10,000.     

Three-dimensional coordinate measurements using a multiple-pinhole interferometer

We propose a method for noncontact measurements of three-dimensional (3D) coordinates based on a Y-typed multiple-pinhole (MP) interferometer and demonstrate its feasibility in experiments. In this method, a Y-typed MP plate is inserted between the target and an image sensor to form a common-path interferometer. The 3D coordinates of the target are found by an effective algorithm using the discrete phase values on the measurement pinholes of the MP plate. These phase values can be directly extracted from a Fourier transform of the recorded intensity pattern without need of any iterative or phase-shifting algorithm. The method could be significant in real-time coordinate measurements and position tracking applications.     

Nonequilibrium dephasing in an electronic Mach-Zehnder interferometer

We study nonequilibrium dephasing in an electronic Mach-Zehnder interferometer. We demonstrate that the shot noise at the beam splitter of the interferometer generates an ensemble of nonequilibrium electron density configurations and that electron interactions induce configuration-specific phase shifts of an interfering electron. The resulting dephasing exhibits two characteristic features, a lobe pattern in the visibility and phase jumps of pi, in good agreement with experimental data.     

Layer iteration calculation of low-energy electron-diffraction by Beeby's multiple scattering method

The interlayer structural propagator in Beeby's multiple scattering method is transformed into a reciprocal space representation. Interlayer multiple scattering events can then be summed to convergence in a layer iteration scheme. LEED spectra calculations for general angles of Ni (001) using 8 phase shifts and up to 49 Bloch waves are reported. A 3–5 eV shift in peak positions is found between calculations using 5 and 8 phase shifts, resolving a recent controversy over different inner potential values used for Ni (001).     

Scanning monochromatic spatial low-coherence interferometer

A scanning spatial low-coherence interferometer (S-LCI), using an off-axis converging single wavelength laser beam as the probe, resembles a conventional or temporal low-coherence interferometer (T-LCI) in signal formation and data processing. However, the S-LCI is advantageous over a T-LCI with the combination of angle resolving and depth discrimination capabilities. The S-LCI is demonstrated by measuring the angle dependent phase shifts among the multiple reflections of a glass plate, with incident angles accurately scaled in the Fourier domain. The refractive index and geometric thickness of the glass plate are simultaneously produced in this one-step measurement.     

Topological phase shift in a cold-atom interferometer

Matter-wave interferences in a four-pulse version of a Ramsey-Bordé atom interferometer have been utilized to study phase shifts. A topological phase shift analogous to the scalar Aharonov-Bohm effect proposed for charged-particle interferences in the presence of a pulsed electrostatic potential has been investigated. The time-dependent potential has been generated by the interaction of a laser field with an induced atomic dipole without spatial variation along the interferometer arms. The atom interferometer has been run with laser-cooled magnesium atoms stored in a magneto-optical trap.Dedicated to H. Walther on the occasion of his 60th birthday     

Adaptive stabilized interferometer with laser diode

We describe a diode laser interferometer with an electronic adaptive system of fringe pattern stabilization and vibrations suppression. The interferometer allows to obtain up to four high-quality images with relative phase shifts. Also an algorithm for fringe pattern processing has been proposed.     

Modeling of the fringe shift in multiple beam interference for glass fibers

A quadratic model is suggested to describe the fringe shift occurred due to the phase variations of uncladded glass fiber introduced between the two plates of the liquid wedge interferometer. The fringe shift of the phase object is represented in the harmonic term which appears in the denominator of the Airy distribution formula of Fabry-Perot’s interferometer. A computer program is written to plot the computed fringe shifts of the described model. An experiment is conducted using liquid wedge interferometer where the fiber of a nearly quadratic thickness variation is introduced between the two plates of the interferometer. The obtained fringe shift shows a good agreement with the proposed quadratic model. Also, it is compared with the previous theoretical shift based on ray optics of semi-circular shape.      

Multiple self-mixing interferometry algorithm based on phase modulation for vibration measurement

A novel algorithm based on a phase modulation and demodulation technique for multiple self-mixing interferometry was proposed in this paper. This algorithm can measure nanoscale vibration in real time and enhance the measurement resolution of a multiple self-mixing interferometer twofold compared with that of a self-mixing interferometer. In this paper, the principles of the method were described in detail, and a phase equation for multiple self-mixing interferometry was derived. Experiments were confirmed by conducting a series of experiments with different amplitudes, different signal-to-noise ratios, and different vibration waveforms. The experimental results showed that the algorithm can rapidly demodulate vibration in real time and indicated good agreement between theory and experiment.     

Automatic processing of fringe patterns in integer interferometers

The purpose of this paper is to describe a new method for determination of the total phase difference of light waves without interference fringe counting. One can build up an interferometer for measurement of displacements in which the displacements are determined only by the final values of intensity regardless of the velocity and any prior displacements that caused the present one. The same thing holds true for vibration, relief parameters and other values to be measured. Such an interferometer is devisable thanks to two underlying ideas: first, the application of controllable phase shift, and secondly, the use of properties of integer divisability.     

Phase-shifting interferometry with feedback control using heterodyne phase detection

A phase-shifting interferometer with feedback control using heterodyne phase detection was developed. A composite heterodyne phase detection method for obtaining feedback signals was proposed. Interference fringe stabilization and accurate pi/2 phase shifts under micrometer-order vibrations were successfully demonstrated using a digital high-speed lock-in amplifier.     

Phase estimation of phase shifts in two arms for an SU(1,1) interferometer with coherent and squeezed vacuum states

We theoretically study the quantum Fisher information(QFI) of the SU(1,1) interferometer with phase shifts in two arms by coherent ? squeezed vacuum state input, and give the comparison with the result of phase shift only in one arm.Different from the traditional Mach–Zehnder interferometer, the QFI of single-arm case for an SU(1,1) interferometer can be slightly higher or lower than that of two-arm case, which depends on the intensities of the two arms of the interferometer.For coherent ? squeezed vacuum state input with a fixed mean photon number, the optimal sensitivity is achieved with a squeezed vacuum input in one mode and the vacuum input in the other.     

Interferometry with Ca atoms

Separated field excitation of a calcium atomic beam using four traveling laser fields represents two distinct atom interferometers utilizing the internal degrees of freedom of the atoms. Phase shifts between the atomic partial waves have been realized by phase shifts of the laser wave fields, by the ac-Stark shift, and by rotation of the interferometer (Sagnac effect). One particular interferometer can be selected by interaction of the atomic waves with extra laser fields. We furthermore report on the preparation of a laser cooled and deflected calcium atomic beam that can be utilized to largely increase the sensitivity of the interferometer.     

相干合成子光束一致性检测研究

分析了激光相干合成装置及其光路调整要求,提出利用剪切干涉检测合成光路中子光束一致性的方法。分析剪切干涉原理,建立了剪切板干涉物理模型,以相干合成中两路矩形光束拼接组束为例,数值模拟并研究了子光束的整体倾斜、离焦所对应的剪切干涉条纹,得到了条纹图像与子光束光轴误差、离焦误差之间的对应关系,用于相干合成光路中子光束光轴和发散角误差的判断。光轴倾斜大于5μrad时,可以直接观察互干涉和自干涉条纹变化,发散角在大于10μrad时,干涉条纹变化明显。此外,剪切干涉的自干涉条纹平移可用来检测子光束间的活塞误差,可作为光束拼接相干合成中闭环相位检测和控制的手段。     

Absolute interferometer for three-dimensional profile measurement of rough surfaces

We present a new interferometer system devised for surface-profile metrology with multiple two-point-diffraction sources that are made from a pair of single-mode optical fibers. The diffraction interferometer system performs an absolute profile measurement by projecting multiple fringe patterns on the object surface and then fitting the measured phase data into a global model of multilateration. Test measurement results demonstrate that the proposed profiling method is suited for rough surfaces with excessive surface irregularities, which are difficult to measure with conventional two-arm interferometers.     

Measurement of surface figure of plane optical surfaces with polarization phase-shifting Fizeau interferometer

A Fizeau interferometer based set up for measurement of surface forms of plane optical surfaces has been discussed. Phase shifting interferometry has been applied using polarization phase shifter. A linearly polarized (632.8 nm) He–Ne laser has been used as the source. Light reflected from the object and the reference/master surfaces are made circularly polarized in opposite senses by means of two properly oriented quarter wave retardation plates placed at appropriate positions, one inside and other outside the interference cavity of the interferometer, and phase shifts are introduced between the object and the reference/master waves by varying angular orientation of a polarizer/analyzer. Final result is made free from any residual wave-front aberrations introduced by the (intra-cavity) wave plate by subtracting phase values obtained by PSI technique between a high optical quality master surface and the reference surface from that obtained for the test object surface with respect to the same reference surface for each point of the interference field. Results are shown for a plane surface.Advantages of the technique presented are linearity and high accuracy in phase stepping, no perturbation of the interference cavity during the phase shifting and possibility of real time or dynamic interferometry.