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The statistical accuracy with which moments of the intensity-fluctuation distributions of optical fields can be determined, by photon-counting experiments of finite duration, is calculated.

The use of scaling for one-bit correlation processing in optical spectroscopy of nongaussian signals is discussed. A theoretical proof of its equivalence with uniform random clipping, and hence full correlation, is provided in certain cases.

Optical measurements by intensity fluctuation spectroscopy are subject to errors arising from the statistical nature of light and of the photo-detection process. The authors report the results of a calculation of the expected errors, due to these causes, in linewidth measurements by digital autocorrelation of photon counting fluctuations.

Direct use of a generalized Laplace transform is proposed for applications in nonequilibrium quantum statistics. The method includes the equilibrium 'double-time' Green's function method as a special case. An example is given in optical theory in which non-Markoffian behaviour and Poincare recurrences have been explicitly found.

Experimental confirmation is presented of recent theoretical results of Jakeman on the time ever aging of photon-counting fluctuations when utilizing clipping techniques for autocorrelation. The effects of finite electronic resolving time (dead-time correction) and finite receiving apertures (spatial-coherence correction) are included.

The effects of finite sizes of source and detector on observed intensity fluctuations of Gaussian light are investigated both theoretically and experimentally. The theory allows a measurement of source size to be made using a single receiving aperture, rather than two as used in the Hanbury-Brown Twiss intensity interferometer.

Discusses the statistical properties of the intensity fluctuations of light fields consisting of an incoherent Gaussian component heterodyned with a single-frequency coherent beam. The second moment of the intensity- fluctuation distribution is obtained in an analytic form for a Lorentzian incoherent spectrum for arbitrary values of the bandwidth and frequency displacement from the coherent mode. The analysis includes as special cases many of the exact results obtained in statistical optics over the last decade.

A straightforward extension of time-dependent quantum-mechanical perturbation theory is made to obtain the equivalent formulae for a statistical mixture of states. The 'master equation' resulting from this procedure is, in its lowest order, the analogue in quantum statistics of the 'Golden Rule' for transition rates and reduces exactly to this form in the limit of pure initial states. The authors give results to fourth order and illustrate their use by applying them to the problem of the resonant interaction of an electromagnetic field and a two-level atom.

An experimental investigation of laser noise by measurement of photon- counting distributions over a range of sample times and pumping levels is reported. These results are compared with theoretical predictions and show good agreement. In addition a simple approximate expression for the second moment of the intensity fluctuations is given.

We discuss the quantum-mechanical problem of intensity fluctuations in samples of Gaussian light and its connection with the corresponding classical scalar problem involving fluctuations of random noise power. We obtain an expression for the intensity-fluctuation distribution of light with a Lorentzian spectrum, and investigate analytically its asymptotic behaviour. Numerical techniques are used to evaluate the distribution for various intermediate linewidths, and some examples of the corresponding theoretical photon-counting distributions are also given.

An optical linewidth of 20 Hz of laser light scattered by spherical particles undergoing Brownian motion has been measured experimentally by photon-counting statistics using the theory of the intensity-fluctuation distribution of Gaussian-Lorentzian light.

We report the results of photon-counting experiments which demonstrate the factorization properties of the correlation functions, up to sixth order, of coherent and incoherent optical fields.

A simple, exact analytic expression is derived for the effective spectral linewidth of laser intensity fluctuations as a function of output power. Relevance of the work to the general theory of second-order phase transitions is pointed out.

The analogue of a theorem of Van Vleck on the spectrum of clipped noise is formulated for use in optical spectroscopy.