Coupling of intersecting diffused waveguides.

We have investigated experimentally and theoretically the coupling of light between intersecting Ti:LiNbO(3) waveguides as a function of the intersection angle, theta. The diffused waveguides are single-mode at 1.3 micron and exhibit low insertion loss (2 dB for both polarizations) with respect to abutted fibers. As expected, the coupling is periodic in cot(theta/2). Over the range of angles examined (0.3 degrees to 3.3 degrees), the coupling could be made to vary from -0.2 dB to a minimum of -12 dB for the TE mode and -15 dB for the TM mode. The period with respect to cot(theta/2) has been estimated for the TE mode using a simple mode and the effective index method. The experimental results are within the range calculated.