The structure of the large eddies in fully developed turbulent shear flows. Part 2. The plane wake

Light energy is coupled between a first optical path including a first channel optical waveguide defined by a selected material diffused into a substrate and a second optical path including a second channel optical waveguide defined by a selected material diffused into the same substrate. The two channel optical waveguides are disposed in substantially non-coupling, co-extensive proximity on the substrate. An area of the same substrate between the two channel optical waveguides is diffused with a material for inducing a determinable degree of coupling between the two optical waveguides but is of insufficient depth of diffusion to support light wave propagation in and of itself in the manner of an optical waveguide. By selectively and controllably varying the amount of diffusion between the channel optical waveguide optimum efficiency of coupling may be achieved therebetween with a desirably high degree of precision through the use of relatively simple and inexpensive fabrication techniques.