Mixing inhomogeneous, partially coherent optical fields.
A phase-quadrature (p-q) description of a random optical field is suggested as an attractive alternative to the usual logamplitude-phase representation for the purpose of investigating the behavior of the optical heterodyne. Using the p-q representation, an expression is developed for the average signal-to-noise ratio at the heterodyne's output when both the signal and local oscillator (LO) fields are inhomogeneous and partially coherent. An examination of the expression for the signal-to-noise ratio indicates the general nature of the previously observed saturation effect. A coherence suppression phenomenon is also apparent. It is shown that the heterodyne's field of view may be drastically broadened (relative to that of a system which processes ideal plane waves) as a result of weak spatial coherence in either the signal or LO field. Recently published experimental data are examined in light of the results obtained i this paper, and good agreement between theory and experiment is observed.
SNR Concept in Underwater Optical Heterodyne Detection Systems.
The SNR for an underwater optical heterodyne detection system is defined and an equation for this ratio is derived. The equation allows computation of the SNR when the fields to be mixed have nonuniform irradiance profiles and are partially coherent. Effects of backscattered light on the SNR are considered. Curves showing the effect of backscattered light on the SNR are presented.
Signal degeneration in laser beams propagated through a turbulent atmosphere
The sta ti s ti cal di s tributi ons of th e a ngle of arrival, th e s pot location, the cross section, th e amp li . tude , th e carrier phase and the modulation phase of a lase r bea m tra ve rs ing an anisotropicaliy turbule nt at mos phere are de rived in terms of the s pace corre la tio n fun c tion of th e at mosph eri c index of refractio n a nd the windspeed. The Limit a ti o ns imposed by the turbule nt atm osp he re and the loss ,of cohe re nce o n the de pth and bandwidth of the modulation , on the le ngth of the path a nd on the a pe rture of the rece iv· ing appara tus are a na lyzed . Experim e nt s to ob tai n num e ri ca l param e ters a nd tn c hf'c k fun c tional depe nde ncies are proposed.