During the last week of June 1960, a three-day conference on the coherence properties of electromagnetic radiation was held on the campus of the University of Rochester. Sponsored by the US Air Force, the University of Rochester, and the Optical Society of America, the purpose of the conference was to bring together optical and atomic physicists from this country and abroad to discuss problems of common interest dealing with the question of coherence throughout the electromagnetic spectrum. To a large extent motivation was supplied by a number of controversial and surprising developments in widely separated branches of physics within the last decade. Certainly much of the attention paid to questions of coherence after so many years of its having lain dormant is due in no small measure to the now famous Brown-Twiss experiment (1955) on the correlation in fluctuations of the output currents of two photoelectric detectors exposed to mutually coherent fields of light. The controversy that followed demonstrated clearly the lack of understanding of the statistical properties inherent in the emission, propagation, and detection of radiation. Whether or not one chose to explain the correlation as a natural tendency for bosons to clump or a natural interference effect among Fourier components in the finite spectral width of every natural source (or both) seemed at first to be a question of taste.
During the last week of June 1960, a three-day conference on the coherence properties of electromagnetic radiation was held on the campus of the University of Rochester. Sponsored by the US Air Force, the University of Rochester, and the Optical Society of America, the purpose of the conference was to bring together optical and atomic physicists from this country and abroad to discuss problems of common interest dealing with the question of coherence throughout the electromagnetic spectrum. To a large extent motivation was supplied by a number of controversial and surprising developments in widely separated branches of physics within the last decade. Certainly much of the attention paid to questions of coherence after so many years of its having lain dormant is due in no small measure to the now famous Brown-Twiss experiment (1955) on the correlation in fluctuations of the output currents of two photoelectric detectors exposed to mutually coherent fields of light. The controversy that followed demonstrated clearly the lack of understanding of the statistical properties inherent in the emission, propagation, and detection of radiation. Whether or not one chose to explain the correlation as a natural tendency for bosons to clump or a natural interference effect among Fourier components in the finite spectral width of every natural source (or both) seemed at first to be a question of taste.
Introduction We will now study the properties of fluctuating electromagnetic fields, paying attention mainly to the optical region of the electromagnetic spectrum. It seems hardly necessary to stress that every electromagnetic field found in nature has some fluctuations associated with it. Even though these fluctuations are, as a rule, much too rapid to be observed directly, one can deduce their existence from suitable experiments that provide information about correlations between the fluctuations at two or more space-time points. The simplest manifestations of correlations in optical fields are the well-known interference effects that arise when two light beams that originate from the same source are superposed. With the availability of modern light detectors and electronic circuitry of very short resolving time, other types of correlations in optical fields began to be studied in more recent times. These investigations, as well as the development of lasers and other novel types of light sources, led to a systematic classification of optical correlation phenomena and the complete statistical description of optical fields. The area of optics concerned with such questions is now generally known as optical coherence theory . The first investigations of coherence phenomena are due to Verdet (1865, 1869) and von Laue (1907a, b). Some early investigations of Stokes (1852) and Michelson (1890, 1891a, b, c, 1892, 1920) although not explicitly mentioning coherence – because this concept is of a much later origin – have also contributed to the clarification and development of this subject.
W1 Resonant Pulse Propagation I.- W1-1 Some Nonlinear Properties of Pulse Propagation.- W1-2 Self-Induced Transparency in the Broadline and Narrowline Limits and Applications.- W1-3 Observation of Zero-Degree Pulse Propagation in a Resonant Medium.- W1-4 Higher Conservation Laws and Coherent Pulse Propagation.- W2 Quantum Electrodynamics and Alternative Theories I.- W2-1 Survey of the Present Status of Neoclassical Radiation Theory.- W2-2 A Test of Jaynes' Neoclassical Theory: Incoherent Resonance Fluorescence from a Coherently Excited State.- W2-3 Experimental Limitations to the Validity of Semiclassical Radiation Theories.- W2-4 Time Delay Statistics of Photoelectric Emissions: An Experimental Test of Classical Radiation Theory.- W3 Coherence Effects in Spontaneous Emission I.- W3-1 Non-Linear Radiation Reaction.- W3-2 Master Equations in the Theory of Incoherent and Coherent Spontaneous Emission.- W3-3 Influence of Resonant Frequency Shifts on Superradiant Damping.- W3-4 Spontaneous Emission Rate in the Presence of a Mirror.- W4 Coherence I.- W4-1 Atomic Coherent States in Quantum Optics.- W4-2 Coherent States in Modern Physics.- W4-3 Debye Representation and Multipole Expansion of the Quantized Free Electromagnetic Field.- W4-4 Volume of Coherence.- T1 Quantum Electrodynamics and Alternative Theories II.- T1-1 A Quantum Treatment of Spontaneous Emission without Photons.- T1-2 Finite Quantum and Classical Electrodynamics.- T1-3 The Use of Classical Solutions in Quantum Optics.- T1-4 Raman Effect in Semiclassical Theory.- T2 Light Scattering I.- T2-1 Theory of Resonant Light Scattering Processes in Solids.- T2-2 A Generalized Extinction Theorem and Its Role in Scattering Theory.- T2-3 Mode Analysis and Mode Coupling of Electromagnetic Fields in Spatially Dispersive Media.- T2-4 Amplitude Stabilization of Pulses from a Q-Switched Ruby Laser by Means of Interaction with a Non-Linear Medium.- T3 Correlation and Fluctuation Measurements.- T3-1 Two-Photon Time Distributions in Mixed Light Beams.- T3-2 Photocounting Inversion in Presence of Dead Time Effects.- T3-3 Image Reconstruction from the Modulus of the Correlation Function: A Practical Approach to the Phase Problem of Coherence Theory.- T3-4 Photon-Correlation Spectroscopy.- T3-5 Multi-Time Intervals Distributions of Photoelectrons from Stationary Pseudo-Thermal Light with Gaussian Spectrum.- T4 Light Scattering II.- T4-1 Adventures in Green's Land: Light Scattering in Anisotropic Media.- T4-2 Intensity Fluctuation Techniques in Light Scattering.- T4-3 Coherence Properties of Light through a Liquid Crystal.- T4-4 C. Non-Critical Rayleigh Scattering from Pure Liquids.- T5 Coherence Effects in Spontaneous Emission II.- T5-1 Cooperative Effects in Spontaneous Emission.- T5-2 Amplified Spontaneous Emission.- T5-3 Non-Gaussian Statistics of Superradiant Radiation from Saturated Xenon 3.5?m Laser Amplifier.- T5-4 On the Theory of Radiating Electrons.- T6 Coherent Light Interactions.- T6-1 Atomic and Molecular Spectroscopy by Saturation with Coherent Light.- T6-2 Response Functions for Strongly Driven Systems.- T6-3 Mechanism of Interaction of Picosecond Light Pulses with Matter Yielding Self-Trapping.- T6-4 Resonance Fluorescence Lineshapes with Intense Applied Fields.- T6-5 Electron Beams as Carriers of Optical Coherence.- T7 Lasers.- T7-1 Detuned Single Mode Laser and Detailed Balance.- T7-2 Tunable Raman Lasers.- T7-3 Dye Lasers: Recent Advances in Tunable Systems.- F1 Quantum Electrodynamics and Alternative Theories III.- F1-1 A Theory of Light without Photons: Implications from Fermis to Light Years.- F1-2 Blackbody Heat Capacity and Action-at-a-Distance Electrodynamics.- F1-3 The Implications of Radiative Equilibrium in Jaynes' Extension of Semiclassical Radiation Theory.- F1-4 A Quantum Electrodynamic Investigation of the Jaynes-Crisp-Stroud Approach to Spontaneous Emission.- F1-5 Critical Comments on Radiation Theory.- F2 Resonant Pulse Propagation II.- F2-1 Cooperative Phenomena in Resonant Propagation.- F2-2 Theory of Sub-Cooperation-Limit Optical Pulses in Resonant Absorbers.- F2-3 Multiple Pulse Chirping in Self-Induced Transparency.- F2-4 Coupled Superradiance Master Equations: Application to Fluctuations in Coherent Pulse Propagation in Resonant Media.- F3 Coherence II.- F3-1 The Laser-Phase Transition Analogy - Recent Developments.- F3-2 Multiple-Time-Scale Analysis of Coherent Radiation.- F3-3 Orthogonal Operators and Phase Space Distributions in Quantum Optics.- F4 Coherence Effects in Spontaneous Emission III.- F4-1 Radiation by Many Excited Atoms between Mirrors.- F4-2 Transient Coherent Emission.- F4-3 Superradiance from a System of 3-Level Particles.- F4-4 A Quantum Electrodynamic View of Superradiance as a Competition between Stimulated and Spontaneous Atomic Decay.- F5 Post Deadline Session.- F5-1 Third- and Higher-Order Intensity Correlations in Laser Light.- F5-2 Correlation Function of a Laser Beam near Threshold.- F5-3 Localization of Photons.- F5-4 Adiabatic Following and the Self-Defocusing of Light in Rubidium Vapor.- F5-5 Experimental Evidence of an X-Ray Laser.- F5-6 Quantum Theory of Photodetection and Coherence Properties of Electrons.- F5-7 Statistics of Light Scattered by Non-Gaussian Fluctuations.- F6 Quantum Noise.- F6-1 Unified Thermodynamics of Dissipative Structures and Coherence in Nonlinear Optics.- F6-2 The Approach to Thermal Equilibrium in Systems of Coupled Quantum Oscillators Initially in a Generalized Gaussian State.- F6-3 Comparison between Incoherent and Chaotic Sources: Contribution to the Study of the Origin of Bunching Effect.- F6-4 Self-Pulsing in Laser Amplification of Broadband Noise.- Author Index.
An account is given of optical coherence theory as it existed in the 1950's when, essentially, only thermal sources and slow detectors were available and it sufficed to characterize the coherence and polarization properties of an electromagnetic field by second-order correlation functions. The necessity for a more sophisticated specification of the coherence properties of fields, involving the use of higher-order correlation functions, first hinted at by the Hanbury-Brown-Twiss experiments and emphasized by the advent of the laser, is then introduced. Both classical and quantum mechanical treatments are discussed, each leading, in almost all cases of practical interest, to similar results. It is seen that the development of fast detectors enabled the higher-order correlation functions to be measured using photon counting techniques and an account of experimental work verifying the complete theory using such techniques is given. The review concludes with a discussion of some developments in associated areas whose origin lies in the resurgence of interest in coherence theory during the last decade.
A review is presented of various investigations on coherence and fluctuations of light which have been carried out within the last few years. In particular some of the research carried out at the University of Rochester and related investigations undertaken elsewhere are described. This research is mainly concerned with the following topics: classical and quantum description of higher order coherence effects, photon correlation and coincidence experiments, stellar correlation interferometry, photon bunching, and the determination of the statistical properties of light from photoelectric counting experiments.
This article presents a review of coherence properties of electromagnetic fields and their measurements, with special emphasis on the optical region of the spectrum. Analyses based on both the classical and quantum theories are described. After a brief historical introduction, the elementary concepts which are frequently employed in the discussion of interference phenomena are summarized. The measure of second-order coherence is then introduced in connection with the analysis of a simple interference experiment and some of the more important second-order coherence effects are studied. Their uses in stellar interferometry and interference spectroscopy are described. Analysis of partial polarization from the standpoint of correlation theory is also outlined. The general statistical description of the field is discussed in some detail. The recently discovered universal "diagonal" representation of the density operator for free fields is also considered and it is shown how, with the help of the associated generalized phase-space distribution function, the quantum-mechanical correlation functions may be expressed in the same form as the classical ones. The sections which follow deal with the statistical properties of thermal and nonthermal light, and with the temporal and spatial coherence of blackbody radiation. Later sections, dealing with fourth- and higher-order coherence effects include a discussion of the photoelectric detection process. Among the fourth-order effects described in detail are bunching phenomena, the Hanbury Brown-Twiss effect and its application to astronomy. The article concludes with a discussion of various transient superposition effects, such as light beats and interference fringes produced by independent light beams.
Introduction In this chapter we will put the concept of coherence on a more mathematical basis. This will involve the formal definition of a number of functions that are used to describe the coherence properties of optical fields. These include the analytic signal, various correlation functions, and the degree of coherence for describing both temporal and spatial coherence. We shall see that the degree of temporal coherence is quantitatively related to the lineshape function and that the degree of spatial coherence between two points is determined by the size, intensity distribution, and location of an illuminating source. We will use the wave equation, and special solutions to the wave equation called Green's functions, to show how spatial coherence varies from point to point. The chapter will conclude with a discussion of how the intensity fluctuations of a source depend on its coherence properties, and we will examine a specific scheme, namely the Hanbury Brown–Twiss experiment, by means of which this relationship is studied. This discussion will involve a discussion of “photon statistics,” namely the time variation of the “detection” of photons from a source. In a quantum-mechanical context, square-law detectors respond to these quantized excitations of the optical field, which we call photons. In classical coherence theory it is advantageous to represent the real electromagnetic field by a complex quantity, both for its mathematical simplicity and because it serves to emphasize that coherence theory deals with phenomena that are sensitive to the “envelope” or average intensity of the field.