1,720,981 research outputs found
PHASE HOLONOMY IN OPTICAL INTERFEROMETRY
No full textThe delivering of two-frequency beams by optical fibres and interferometers and the interference of polarized waves is studied by using Jones' formalism and the complex-wave representation. Polarization encoding is shown to make the relation between the phase of the interference pattern and the difference in the optical path of interfering beams nonlinear, owing to the geometric contribution to the phase made by misalignments and unequal ellipticity of the normal modes of beam and interferometer. The polarization transport is analysed with the aid of the Poincare representation, and a complete picture of the phenomena underlying nonlinearity and geometric noise is given. In the case of small aberrations approximate formulae and experimental observations are reported as well
OBSERVATION OF FRESNEL DIFFRACTION IN A 2-BEAM LASER INTERFEROMETER
No full textA displacement-angle interferometer capable of 10(-6) resolution in fringe division was developed for the precise measurement of the silicon (220) lattice spacing by x-ray and optical interferometry. With a view to achieving 10(-8) measurement uncertainty, the interference pattern was studied by the Fresnel (Gaussian) scalar approximation of the free-space propagation of interfering beams. Imperfect alignment and diffraction phenomena having been identified, and subsequently experimentally proved, as important error sources, remedial steps were identified and taken with consequent improvement of the experiment accuracy. The investigation brought into light theoretical and experimental evidences of corrections to the interference phase which were overlooked in previous analyses
PHASE MODULATION IN HIGH-RESOLUTION OPTICAL INTERFEROMETRY
No full textThe measurement of nanometre displacements with picometre resolution has been made possible by a phase-modulation recovery scheme applied to an optical Michelson interferometer using polarization encoding. In contrast to conventional schemes, phase modulation is carried out before the interferometer optics. In this way, the low-frequency components of the phase shift between the two interfering beams are locked at zero (within limits set only by shot noise) before beam splitting by a feedback loop driving the modulator. An interferometer prototype, illuminated by a beam thus modulated, was constructed and coupled to an X-ray interferometer to compare the optical and X-ray interferometric measurement values of sub-nanometre displacements. A resolution better than 1 pm over a 100 Hz bandwidth was obtained
Beam-astigmatism in laser interferometry
No full textWe have developed a null laser interferometer capable of picometer resolution in fringe division for the measurement of the silicon (220) lattice spacing by X-ray interferometry., With a view to achieving 10(-9) measurement uncertainty, we hale given special attention to the effects of diffraction, An analysis of the measurements which has brought to Light wavefront astigmatism? the effect of which had so far been overlooked, is presented, This article show's how astigmatism affects measurements, describes how we determine beam parameters, and compares theoretical and experimental results
Measuring small lattice distortions in Si-crystals by phase-contrast x-ray topography
No full textX-ray phase-contrast topography has been improved by using phase modulation and computing techniques to determine lattice distortions inside near-perfect Si monocrystals. The technique presented is based on the detection of the spatially varying phase shift at the output of a monolithic x-ray interferometer of the triple Laue type using phase modulation and a multi-element detector. Information was obtained about the degree of perfection of crystals being used in the determination of the (220) lattice plane spacing of silicon and of the Avogadro constant
Simulation of the thermoelastic behavior of an LLL x-ray interferometer
No full textIn order to achieve the strictest tolerances required in the manufacturing of an x-ray interferometer of the triple Laue type (LLL) to be used in the accurate determination of the silicon lattice parameter, a new shape of the analyzer crystal is considered. The simulation of its behavior proves that, if specified elastic and thermal load upper limits are satisfied, the lattice plane deformations are compatible with a measurement uncertainty of a few parts in 10(9). (C) 2000 American Institute of Physics. [S0034-6748(00)02004-9]
Optically polished surfaces parallel to the (220) lattice planes of silicon monocrystals (vol 10, pg 549, 1999)
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