Phase Shift Correction Research Articles

Precise wavelength measurements and optical phase shifts II Applications

This paper calculates the optical phase shifts on reflection from dielectric coated mirrors. The technique consists of measuring the transmission spectrum of the mirrors. These data are fitted with a theoretical expression based on an equivalent, quarter-wave stack. This expression then gives the phase-shift corrections for the mirrors. A fast algorithm, based on a series representation for Chebyshev polynomials, calculates the reflectivity and phase shift for a single wavelength in 3 sec in basic on an inexpensive home computer. An application is to measure absolute wavelengths with equipment commonly present in laser laboratories, namely, scanning Fabry–Perot interferometers with dielectric coated mirrors. The method is that of exact fractions, which requires one primary wavelength standard, with a less accurate, secondary standard (or wavemeter). The accuracy of the technique is equal to that of the primary standard. The precision is that of reading the interferometer and can be many times that of the secondary standard.

Experimental investigation of the acoustooptic interaction in a waveguide interferometer

An experimental investigation was made of the transfer characteristics and signal readout efficiency of devices utilizing surface acoustic waves. The investigation was carried out using a strip optical waveguide interferometer. A prototype of this interferometer was made from a YZ-cut lithium niobate substrate. Electrodes were used for electrooptic correction of ihe initial phase shift between the optical waves in the interferometer arms and an opposed-comb transducer was employed to excite acoustic waves. The results should be useful in the development of signal

Extended energy loss fine structure in reflection electron energy loss spectra of Cu and Ni

Reflection electron energy loss spectra of the surfaces of polycrystalline Cu, Ni and Al have been recorded with impact energies ranging from 300 to 2400 eV. Weak structures observed in the M- and L-shell continua of Cu and Ni are interpreted as extended energy loss fine structure (EXELFS), the electron scattering analog of EXAFS. The nearest neighbour spacings derived from the M 23 EXELFS are 0.2 to 0.3 Å less than the values for bulk Cu or Ni. This difference is attributed at least in part to the inaccuracy of calculated phase shift corrections rather than a surface contraction of this magnitude. Complications to reflection EXELFS from multiple plasmon losses are demonstrated in the aluminum L 23 spectrum.

Sound power determination from surface intensity measurements on a vibrating cylinder

The feasibility of using surface intensity measurements for the determination of sound power as a tool for noise source identification was studied with an experiment on a circular cylinder. This cylinder was an idealized model of a muffler shell of a heavy diesel truck. Two experiments were performed with the cylinder excited by an electromagnetic shaker. In the first one, the shaker was driven with a one-third octave band of white noise centered at 6300 Hz and in the second experiment it was driven with broadband white noise between 1000 and 5000 Hz. The sound power measurements were made in a reverberant room and the reverberant room method was used to provide a comparison with the sound power levels obtained from the surface intensity measurement. The acoustic surface intensity was computed from the cross-spectral density between the acoustic pressure and the normal surface velocity of the cylinder. An equation was developed to allow for inclusion of a correction for phase shifts that were caused by the instrumentation and by the finite distance between the microphone and the vibrating surface. The phase shift resulting from this distance was found to have a dominant effect in the higher frequency range and it was important to make these phase-shift corrections in order to obtain accurate measurements of sound power. After including these phase-shift corrections, reasonably good agreement was achieved between the sound power levels obtained from the surface intensity measurements and those from the reverberant room method.

Frequency-swept detector for ion cyclotron resonance mass spectrometers

Design, construction, performance, and use of a frequency-swept bridge detector for ion cyclotron resonance mass spectrometry are described. Special features include characterization and simple automatic correction of phase shift to allow broadband detection. The result is a detection system that may be used either at constant field or constant frequency. Drift-mode operation is simplified in that it may be satisfactorily used without the various signal modulation schemes used in previous detectors. In the trapped mode the detector may be pulsed to control the timing of ion detection. This detector makes it possible to do frequency-swept double resonance experiments which provide spectra of all the product ions of a given reactant ion. Circuit schematics and typical frequency- and field-swept spectra are shown.

Phase filtering with time reversal

Correction of phase shift by time-reversal recording is discussed from a unified viewpoint, including considerations of physical realisability, time delay and a systematic approach to practical application.

Properties of the native oxide on GaSb

This paper reports on the optical and electrical properties of thin (t<3000 A) anodic oxides on p‐type GaSb. The oxides were grown in a 10−1N solution of KOH in methanol at constant current. Thin film interference techniques with phase shift and reflectivity corrections are used to determine the thickness, refractive index, and dispersion of the films in the range 2500<λ<8000 A. MOS structures were prepared and the conductivity, dielectric constant (K=8.5), and breakdown strength (200 V/μm) are determined. At 77 K C–V curves show the surface is normally depleted at zero bias. The resulting C–V curves are compared with the ideal and a typical density of states of 1.0×1012 s/cm−2 eV−1 is measured.

Phase-shift corrections in determining the thicknesses of transparent films on reflective substrates : W. A. Pliskin, Solid-St. Electron., 11 (1968), p. 957

Phase-shift corrections in determining the thicknesses of transparent films on reflective substrates : W. A. Pliskin, Solid-St. Electron., 11 (1968), p. 957

Phase-shift corrections in determining the thicknesses of transparent films on reflective substrates

Thicknesses of transparent films on reflective substrates are being measured non-destructively by CARIS (constant angle reflection interference spectroscopy) and by VAMFO (variable angle monochromatic fringe observation). Both cases are based on the interference between the radiation reflected from the dielectric-air interface and that from the dielectric-substrate interface. For most accurate thickness measurements phase-shift thickness corrections must be made due to the phase-shift on reflection at the two interfaces not being equal. Phase-shift thickness corrections have been calculated for various insulating films on commonly used substrates. In addition universal type charts are presented which simplify the calculation of phase-shift thickness corrections for metals or semiconductors which are bare or covered with a transparent dielectric film.

Molecular Structure of XeF6. I. Analysis of Electron-Diffraction Intensities

A gas-phase electron-diffraction investigation of xenon hexafluoride has been carried out in an effort to obtain structural information which might shed light on the curious properties of the compound. Elaborate precautions were taken to prevent decomposition or contamination of the sample (99.8 mole % pure). Several innovations were introduced into the structure analysis to minimize difficulties encountered in conventional analyses of molecules containing both heavy and light atoms. Two different sets of analyses (I and II) employing two different levels of approximation in electron scattering theory were conducted to test the adequacy of the expressions usually adopted. Analysis I was based on Hartree–Fock x-ray elastic scattering factors, Heisenberg–Bewilogua inelastic scattering factors, and (modified) Born phase-shift corrections for Thomas–Fermi atomic fields. Improvements in Analysis II included the new electron elastic scattering factors and Born phase-shift corrections calculated by the partial wave method by Cox and Bonham, and Hartree–Fock inelastic scattering factors. The Hartree–Fock phase-shift correction was not in complete agreement with experiment but was markedly better than the Thomas–Fermi correction. The effect of ionic character on phase shift was investigated theoretically and shown to be significant. A mean Xe–F bond length of 1.890 ± 0.005 Å was found, but the radial distribution function for Xe–F bonds corresponded to that of a composite for nonequivalent bonds. Amplitudes of bending oscillations are notably large. The diffraction data are not compatible with a regular octahedral XeF6 molecule vibrating in independent normal modes. A more detailed exposition of alternative structures and internal motion is presented in Paper II.

Reflectivity Thickness Corrections for Silicon Dioxide Films on Silicon for VAMFO [Letter to the Editor

In recent years, a great deal of interest has been centered on the non-destructive measurement of the thicknesses of oxide or glass films on silicon, based on the production of interference fringes by varying the angle of observation (VAMFO—variable angle monochromatic fringe observation 1–3 ) or by spectrophotometric variation of the observed wavelength of radiation. 4–7 The film thickness d can be determined from d = (Nλ/2n 2 cos θ 2 ) + Δt φ + Δt r , (1) where N is the order given by N = 1/2, 3/2, 5/2, ··· for minima; n 2 is the SiO 2 refractive index at wavelength λ; θ 2 is the angle of refraction in the SiO 2 ; Δt φ is the phase shift correction; and Δt r is the reflectivity correction.