Coupling of intersecting Ti:LiNbO_3 diffused waveguides

Abstract

In this paper, we have investigated experimentally and theoretically the coupling of light between intersecting Ti:LiNbO3 waveguides as a function of the intersection angle θ. The diffused waveguides are single mode at 1.3 μm and exhibit low insertion loss (≲2 dB for both polarizations) with respect to abutted fibers. Over the range of angles examined (0.3–3.3°), 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. As expected, the coupling is periodic in cot(θ/2); the period has been estimated theoretically for the TE mode using a simple model and the effective index method. The experimental results are within the range calculated.