Type Of Interferometry Research Articles

Impact of Cyclic Error on Absolute Distance Measurement Based on Optical Frequency Combs.

Absolute distance measurements based on optical frequency combs (OFCs) have greatly promoted advances in both science and technology, owing to the high precision, large non-ambiguity range (NAR), and a high update rate. However, cyclic error, which is extremely difficult to eliminate, reduces the linearity of measurement results. In this study, we quantitatively investigated the impact of cyclic error on absolute distance measurement using OFCs based on two types of interferometry: synthetic wavelength interferometry and single-wavelength interferometry. The numerical calculations indicate that selecting a suitable reference path length can minimize the impact of cyclic error when combining the two types of interferometry. Recommendations for selecting an appropriate synthetic wavelength to address the tradeoff between achieving a large NAR and minimizing the risk of failure when combining the two methods are provided. The results of this study are applicable not only in absolute distance measurements but also in other applications based on OFCs, such as surface profile, vibration analysis, etc.

Quantum Interferometry for Different Energy Landscapes in a Tuneable Josephson Junction Circuit

This paper presents a simple Josephson-junction circuit with two parameters (inductance and capacitance) which can be tuned to represent different energy landscapes with different physical properties. By tuning this quantum circuit through external accessible elements we can move from two to three and more energy levels depending on the parameter setting. The inductance, the capacitance as well as the external voltage (driving terms) condition the number of relevant energy levels as well as the model to be used. We show that the quantized circuit represents a multi-state system with tunneling induced by the Landau-Zener and Landau-Zener-Stückelberg transition. The special cases of single crossing and multi-crossing models are thoroughly studied and the transition probability is obtained in each case. It is proven that, the crossing time as well as the relaxation time affect drastically the transition probability; the system mimics a single passage for short relaxation and a multiple passage problem for large relaxation. The nonlinearity of energy levels modifies the transition probability and the derived adiabatic parameters help to redefine the Landau-Zener probability. The observed constructive and destructive interferences are parametrically conditioned by the initial condition set by the inductive branch. Moreover, the total population transfers as well as the complete blockage of the system are obtained in a permissible range of parameters only by changing the values of the inductance. Therefore, the system models a controllable level-crossing where the additional branches (inductive and capacitive) help in designing the number of states, the type of interferometry as well as the control of states occupation.

Quantum metrology with atom and light correlation

The measurement of physical quantities and measurement units standard promote the development of metrology. Especially, the developments of laser interference and atomic frequency standard bring a revolutionary leap for metrology. Many precision measurement techniques have been proposed and experimentally demonstrated, such as gravitational wave measurements and laser gyroscopes based on laser interferometry, and atomic clocks and atomic gyroscopes based on the atom interferometry. Recently, a new branch of science, quantum metrology, has grown up to further explore and exploit the quantum techniques for precision measurement of physical quantities.#br#This paper will focus on recent developments in quantum metrology and interference based on coherence and correlation of light and atom. Firstly, we briefly review the development of metrology. Then, we introduce our own researches in recent years, including quantum-correlation SU(1,1) optical interferometer based on four wave mixing process in atomic vapor and the atom-light hybrid interferometer based on Raman scattering in atomic vapor.#br#Interferometer is a powerful tool to measure physical quantities sensitive to the inference wave with high precision, and has been widely used in scientific research, industry test, navigation and guidance system. For example, the laser interferometer is able to measure optical phase sensitive quantities, including length, angular velocity, gravitational wave and so on. Meanwhile, the atom interferometer is sensitive to the change of atomic phase caused by the light, gravity, electric and magnetic fields. As a new type of interferometry, the atom-light hybrid interferometer, is sensitive to both the optical phase and atomic phase. Furthermore, SU(1,1) interferometer and nonlinear atom-light hybrid interferometer have the ability to beat the standard quantum limit of phase sensitivity. Quantum interference technology, whose phase measurement accuracy can break through the limit of standard quantum limit, is the core of quantum metrology and quantum measurement technology.

Seismic interferometry by multidimensional deconvolution without wavefield separation

S U M M A R Y Seismic interferometry comprises a suite of methods to redatum recorded wavefields to those that would have been recorded if different sources (so-called virtual sources) had been activated. Seismic interferometry by cross-correlation has been formulated using either two-way (for full wavefields) or one-way (for directionally decomposed wavefields) representation theorems. To obtain improved Green’s function estimates, the cross-correlation result can be deconvolved by a quantity that identifies the smearing of the virtual source in space and time, the so-called point-spread function. This type of interferometry, known as interferometry by multidimensional deconvolution (MDD), has so far been applied only to one-way directionally decomposed fields, requiring accurate wavefield decomposition from dual (e.g. pressure and velocity) recordings. Here we propose a form of interferometry by multidimensional deconvolution that uses full wavefields with two-way representations, and simultaneously invert for pressure and (normal) velocity Green’s functions, rather than only velocity responses as for its one-way counterpart. Tests on synthetic data show that two-way MDD improves on results of interferometry by cross-correlation, and generally produces estimates of similar quality to those obtained by one-way MDD, suggesting that the preliminary decomposition into upand downgoing components of the pressure field is not required if pressure and velocity data are jointly used in the deconvolution. We also show that constraints on the directionality of the Green’s functions sought can be added directly into the MDD inversion process to further improve two-way multidimensional deconvolution. Finally, as a by-product of having pressure and particle velocity measurements, we adapt oneand two-way representation theorems to convert any particle velocity receiver into its corresponding virtual dipole/gradient source by means of MDD. Thus data recorded from standard monopolar (e.g. marine) pressure sources can be converted into data from dipolar (derivative) sources at no extra acquisition cost.

Resolving microstructures in Z pinches with intensity interferometry

Nearly 60 years ago, Hanbury Brown and Twiss [R. Hanbury Brown and R. Q. Twiss, Nature 178, 1046 (1956)] succeeded in measuring the 30 nrad angular diameter of Sirius using a new type of interferometry that exploited the interference of photons independently emitted from different regions of the stellar disk. Its basis was the measurement of intensity correlations as a function of detector spacing, with no beam splitting or preservation of phase information needed. Applied to Z pinches, X pinches, or laser-produced plasmas, this method could potentially provide spatial resolution under one micron. A quantitative analysis based on the work of Purcell [E. M. Purcell, Nature 178, 1449 (1956)] reveals that obtaining adequate statistics from x-ray interferometry of a Z-pinch microstructure would require using the highest-current generators available. However, using visible light interferometry would reduce the needed photon count and could enable its use on sub-MA machines.

Estimating ellipticity of a fiber core using two types of interferometry

In the present work two types of low-coherence interferometry are used to estimate the ellipticity of the core of an optical fiber in the cross section. Using the time-domain low-coherence interferometry the group-index difference between the degenerate high-order modes is measured. Because of the usage of a short fiber sample the group-index difference between the degenerate fundamental modes is too small to measure. Secondly, a frequency-domain low-coherence interferometry is presented in details. Since it is an all-fiber setup, longer fiber is allowed to be used. The high-order modes are filtered. The group-index difference between the degenerate fundamental modes is obtained. For each of the methods the experimental results are used to estimate the ellipticity of the fiber core in numerical simulations.

Geometric Landau-Zener Interferometry

We propose a new type of interferometry, based on geometric phases accumulated by a periodically driven two-level system undergoing multiple Landau-Zener transitions. As a specific example, we study its implementation in a superconducting charge pump. We find that interference patterns appear as a function of the pumping frequency and the phase bias, and clearly manifest themselves in the pumped charge. We also show that the effects described should persist in the presence of realistic decoherence.

Deghosting, Demultiple, and Deblurring in Controlled-Source Seismic Interferometry

With controlled-source seismic interferometry we aim to redatum sources to downhole receiver locations without requiring a velocity model. Interferometry is generally based on a source integral over cross-correlation (CC) pairs of full, perturbed (time-gated), or decomposed wavefields. We provide an overview of ghosts, multiples, and spatial blurring effects that can occur for different types of interferometry. We show that replacing cross-correlation by multidimensional deconvolution (MDD) can deghost, demultiple, and deblur retrieved data. We derive and analyze MDD for perturbed and decomposed wavefields. An interferometric point spread function (PSF) is introduced that can be obtained directly from downhole data. Ghosts, multiples, and blurring effects that may populate the retrieved gathers can be locally diagnosed with the PSF. MDD of perturbed fields can remove ghosts and deblur retrieved data, but it leaves particular multiples in place. To remove all overburden-related effects, MDD of decomposed fields should be applied.

Interferometric electromagnetic Green's functions representations using propagation invariants

SUMMARY Creating new responses from cross-correlations of responses measured at different locations is known as interferometry. Each newly created response represents the field measured at one of the receiver locations as if there were a source at the other. Here, we formulate electromagnetic interferometric Green's functions representations in open configurations. There are in principle no restrictions on the heterogeneity and anisotropy of the medium inside or outside the domain. Time-correlation type formulations rely on conservation of total wave energy and they cannot be used for media showing relaxation of some form in a straightforward way. Time-convolution type propagation invariants are independent of the medium relaxation mechanisms and they can be used for interferometry by cross-correlating a measured response with the time-reverse of another response. This type of interferometry can only be formulated in the configuration with one receiver outside the domain. For time-convolution interferometry no restrictions on the medium heterogeneity, anisotropy or relaxation mechanisms are made. For these interferometric formulations to be of practical use, the main simplification is to make a high-frequency approximation for the normal derivative in the source coordinate. These approximations of the exact result lead to two different types of errors. We discuss the causes and consequences of these errors and illustrate them with numerical examples.

Diffraction in Time and a New Type of Interferometry with Nonseparated Beamsa

Diffraction in Time and a New Type of Interferometry with Nonseparated Beamsa

A DECONVOLUTION TECHNIQUE FOR HUBBLE SPACE TELESCOPE FGS FRINGE ANALYSIS

ABSTRACT A technique has been developed for directly transforming interferometer fringe visibility functions (''S-curves") from the HST Fine Guidance Sensors (FGSs) into intensity profiles of the program object. In a process analogous to Fourier transform image deconvolution, an S-curve from a double star yields a pair of narrow profiles containing information on the separation (in one coordinate), and relative brightness of the two stars. The procedure has yielded high internal precision for the separation and relative brightness in tests with HST data. Simulations indicate that it can also deconvolve S-curves from multiple stars or continuous intensity distributions such as resolvable stellar or extra-galactic objects. Similar deconvolution analyses may be useful in other types of interferometry.

Interferometry Based on the Partially Coherent Effect Lying between the Talbot and Lau Effects

Abstract Based on the partially coherent effect that lies between the Talbot effect and the Lau effect, a novel type of interferometry is proposed in this paper for a general configuration. The resultant interferogram is characterized by two different grating-like carriers. Such an interferometer becomes a Talbot or a Lau interferometer by adjusting the source slit to one or other of the two extremes of coherence. The partially coherent effect and the performance of the interferometer are analysed in detail in terms of the ambiguity function. Experimental results are shown to be in good agreement with the predicted intensity distributions.

Stabilized transverse Zeeman laser as a new light source for optical measurement

The light emitted by a stabilized 633-nm He-Ne transverse Zeeman laser (STZL) is composed of two linearly polarized components that are perpendicular to each other. Optical frequencies of the two components are different, and therefore the light changes its polarization with time. The change is represented on the Poincaré sphere as a spin along the equator containing S(2) and S(3) axes of the sphere. Three types of polarimetry and two types of interferometry using an STZL are proposed and experimentally demonstrated. Comparisons of these techniques with the existing ones are also reported.

Interferometric Measurement of Wave-Front Aberrations in Gratings and Echelles*

Modern production of diffraction gratings requires rapid and reliable methods of evaluating quantitatively the wave fronts produced, to determine errors in blank figure and groove positioning. Comparison of methods, including cross ruling, moiré patterns with replicas, Foucault knife-edge tests, phase contrast determinations, and various types of interferometry, supplemented by determinations of ghost intensities, indicates that for errors greater than about λ/40, comparison of the wave front with that from a reference mirror in a Michelson interferometer used in the Twyman-Green manner gives the most nearly adequate conditions for good visibility and sensitivity. Tests at great diffraction angles, necessary for high sensitivity, give patterns of higher contrast and greater intensity than those obtained with the Fizeau plano-interferometer. Exposure times of 10 sec give all needed information about errors.Analysis of the straight-line fringe system obtained shows that in a given order m, a spacing error expressed in fringes is given by Δa=a/m per fringe deviation in the interference pattern, if the spacing constant a is also expressed in fringes. The spacing error per fringe aberration in the interferometer has the same absolute value for all gratings and echelles, irrespective of their spacing constant, provided that the interferograms are taken at the same angle of incidence, and in light of the same wavelength. This provides an important way of directly comparing the quality of various diffraction instruments, and of estimating their intrinsic resolving powers separate from the aberrations of other components of the spectrograph, which affect the limit of resolution.Uniqueness of interpretation of the interferograms can be ascertained by taking interferograms of the same grating area in two suitably selected orders, with a graduated reference scale placed directly on the grating surface showing in both.