Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE

Generalized quantitative approach to two-beam fringe visibility (coherence) with different polarizations and frequencies

Chandrasekhar Roychoudhuri, A. Michael Barootkoob

Published Jul 17, 2008• 7 citations

Abstract

All two-beam interferometry eventually reduces to quantitative measurement of the effective fringe visibility (or degree of coherence) in some form. We present generalized analytical and experimental results of visibility for the cases of two beam Poynting vectors both collinear (scanning fringe mode) and non-collinear (spatial fringe mode) with different polarizations and frequencies. This leads to a much broader and deeper understanding of the roles of material dipoles (beam splitters & detectors; both classical and quantum) in measured coherence effects that are not explicitly addressed in the traditional coherence theory. Coherence theory should be presented as correlation between sensing dipole undulations that are simultaneously induced by superposed light beams rather than as correlation between the optical fields. This generalized understanding of the physical processes behind coherence phenomenon will open up (i) better understanding of the nature of light and (ii) many more innovative approaches to quantitative interferometry.

DOI: 10.1117/12.793747

Related papers

Exploring measurement processes behind fringe visibility and its representation by correlation function

Chandrasekhar Roychoudhuri

To accommodate light-detector interaction processes explicitly, the optical coherence should be represented by correlation of simultaneous dipolar stimulations of detecting molecules induced by superposed classical optical fields, rather than correlations between the optical fields themselves.

Frontiers in OpticsJan 1, 20120 citations

Reality of superposition principle and autocorrelation function for short pulses

Chandrasekhar Roychoudhuri

We "see" light only when some material detectors (dipoles) respond to the incident EM field. EM fields do not operate on each other to make themselves visible to us. Superposition of multiple fields becomes manifest only when the intrinsic properties of these dipoles allow them to respond to all the superposed fields simultaneously and thereby summing the effects of all the fields. Accordingly, depending upon the different intrinsic properties of the detectors and the physical conditions of measurements (integration times, etc.) the manifestation of the "coherence" properties for the same set of superposed fields could be different. It is then prudent to represent the autocorrelation function for superposed fields in terms of the dipole undulation of the detectors rather than the fields themselves. Then the physics of the detectors and the measurement conditions automatically becomes an inherent part of the discussion on coherence. We illustrate our premise by presenting the analysis to understand the behavior of beam splitters, two-beam interferometers and an N-beam grating "interferometer" in terms of the autocorrelation functions due to a short pulse as would be experienced by the material dipoles of the beam splitters and detectors. Our approach reveals that superposition effects to become manifest the multiple fields must be physically superposed simultaneously on the detecting dipoles and hence the process is causal.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIEFeb 9, 200613 citations

Comment on “Quantitative wave-particle duality in multibeam interferometers”

Giuseppe Bimonte, R. Musto

In a recent paper, D\"urr [Phys. Rev. A 64, 042113 (2001)] proposed an interesting multibeam generalization of the quantitative formulation of interferometric wave-particle duality, discovered by Englert for two-beam interferometers. The proposed generalization is an inequality that relates a generalized measure of the fringe visibility to certain measures of the maximum amount of which-way knowledge that can be stored in a which-way detector. We construct an explicit example where, with three beams in a pure state, the scheme proposed by D\"urr leads to the possibility of an ideal which-way detector that can achieve a better path discrimination at the same time as a better fringe visibility. In our opinion, this seems to be in contrast with the intuitive idea of complementarity, as it is implemented in the two-beams case, where an increase in path discrimination always implies a decrease of fringe visibility, if the beams and the detector are in pure states.

arXiv:quant-ph/0304004Physical Review AJun 11, 200328 citations

Vector-light quantum complementarity and the degree of polarization

Andreas Norrman, Ari T. Friberg, Gerd Leuchs

The dual wave–particle nature of light and the degree of polarization are fundamental concepts in quantum physics and optical science, but their exact relation has not been explored within a full vector-light quantum framework that accounts for interferometric polarization modulation. Here, we consider vector-light quantum complementarity in double-pinhole photon interference and derive a general link between the degree of polarization and wave–particle duality of light. The relation leads to an interpretation for the degree of polarization as a measure describing the complementarity strength between photon path predictability and so-called Stokes visibility, the latter taking into account both intensity and polarization variations in the observation plane. It also unifies results advanced in classical studies by showing that the degree of polarization can be viewed as the ability of a light beam to exhibit intensity and polarization-state fringes. The framework we establish thus provides novel aspects and deeper insights into the role of the degree of polarization in quantum-light complementarity and photon interference.

OpticaJan 22, 202030 citations

Complex degree of coherence and fringe visibility in spatial unitary transformations of scalar fields

Atri Halder, Ari T. Friberg

We study the effects of spatial unitary transformations on the complex degree of coherence and the visibility of intensity fringes in Young’s double pinhole interference setup with scalar light. We demonstrate that the degree of coherence and the visibility, in general, change in such transformations and may become zero for the output fields even when the input beams are correlated. Moreover, we explore the influence of unitary two-beam transformations on the complementarity relations associated with the degree of coherence, the intensity distinguishability, and the concurrence. We illustrate the results with the help of Gaussian Schell-model beams. Nonabsorbing beam splitters, which are key elements in optical systems, are practical realizations of spatial unitary transformations.

Optics LettersDec 20, 20193 citations

A Deeper Look at the Fundamentals of Heterodyne Detection Requirements

Chandrasekhar Roychoudhuri, Narasimha S. Prasad

We generally accept the experimentally observed criteria for heterodyne detections that the two waves that are mixed must (i) be collinear, (ii) have matched wave fronts and (iii) cannot be orthogonally polarized. We have not found in the literature adequate physical explanations for these requirements. The purpose of this paper is to find deeper physical understanding of the coherent heterodyne detection processes that could lead to better coherent laser radar system designs1. We find that there are a number of unresolved paradoxes in classical and quantum optics regarding the definitions and understanding of the "interference" and "coherence" properties of light, which are attributed as essentially due to inherent properties of the EM waves. A deeper exploration indicates that it is the various quantum mechanical properties of the detecting material dipoles that make light detectable (visible, or measurable) to us. Accordingly, all the properties that we generally attribute to only light, are in reality manifestations of collective properties of dipole-light interactions. "Interference" and "coherence" can be better understood in terms of this mutual interaction, followed by energy absorption by the dipoles from EM wave fields, manifesting in some measurable transformation of the detecting dipoles. Light beams do not interfere by themselves. The superposition effects due to light beams become manifest through the response characteristics of the detecting dipoles. In this paper, we will show some preliminary expe rimental results that clearly demonstrate that the heterodyning wave fronts have quantitative degradation in signal generation as the angle between them deviates from perfect collinearity. Subsequently, we will propose a hypothesis for this behavior. We will present experimental data establishing that the so called incoherent light can be detected through heterodyne mixing as long as the pulse length contained in the "incoherent" light is longer than the response time of the detector. We will also present a correspondingly better interpretation of two distinguishable coherence properties, temporal coherence and spectral coherence. Our investigation provides a deeper insight into how to rela x various system requirements for heterodyne detection and accordingly develop systems that are simpler, more reliable and lower in cost. Also, we believe that engineering of detector architecture by appropriately modifying dipole behavior using emerging nanotechnology to optimize heterodyne efficiency will be advantageous.

Jul 8, 20072 citations