Experimental Approaches to the Phase Problem of Optical Coherence Theory.

Terry van Dijk

Demosthenes Dialetis, E. Wolf

Baris I. Erkmen, Jeffrey H. Shapiro

Optical coherence theory for the complex envelopes of passband fields has been concerned, almost exclusively, with correlations that are all phase insensitive, despite decades of theoretical and experimental work on the generation and applications of light with phase-sensitive correlations. This paper begins the process of remedying that deficiency, by developing coherence theory for classical scalar fields with phase-sensitive fluctuations. In particular, the Wolf equations are extended to phase-sensitive fields, paraxial free-space propagation effects are analyzed, and a normal-mode decomposition for scalar fields of arbitrary coherence is established. The extension of this theory to the field-operator description that is needed to characterize non-classical light beams is briefly discussed.

R.W. Smith

Jan Olof Stenflo

The symmetric peak observed in linear polarization in the core of the solar sodium D 1 line at 5896 Å has remained enigmatic since its discovery nearly two decades ago. One reason is that the theory of polarized scattering has not been experimentally tested for multi-level atomic systems in the relevant parameter domains, although the theory is continually being used for the interpretation of astrophysical observations. A laboratory experiment that was set up a decade ago to find out whether the D 1 enigma is a problem of solar physics or quantum physics revealed that the D 1 system has a rich polarization structure in situations where standard scattering theory predicts zero polarization, even when optical pumping of the m state populations of the hyperfine-split ground state is accounted for. Here we show that the laboratory results can be modeled in great quantitative detail if the theory is extended to include the coherences in both the initial and final states of the scattering process. Radiative couplings between the allowed dipole transitions generate coherences in the initial state. Corresponding coherences in the final state are then demanded by a phase closure selection rule. The experimental results for the well understood D 2 line are used to constrain the two free parameters of the experiment, collision rate and optical depth, to suppress the need for free parameters when fitting the D 1 results.

Kyo Inoue, Shogo Kitahara, Koji Igarashi

Coherent Ising machines (CIMs) are optical computers designed to solve combinatorial optimization problems based on the Ising model. Among several variants, the optical-loop-based CIM, which utilizes optical pulses with binary phases circulating in a loop equipped with a pulse-pumped phase-sensitive amplifier (PSA) and a measurement feedback circuit, has experimentally demonstrated high performance in terms of the number of pulses and connectivity. This study numerically investigates the dependence of its calculation performance on operating conditions such as the noise level, coupling strength between pulses, and PSA pump increment rate. The CIM solving Max-Cut problems is simulated using a difference equation based on a traveling-wave model under various operating conditions. The results indicate that noise is not a critical factor, there is an optimal condition for the coupling strength, depending on the graph structure, and slower pump-increment rate leads to higher scores. Under optimal conditions, the simulation produces better calculation results than those previously reported in an experimental study.