Control of directional evanescent coupling in fs laser written waveguides

We investigate the evanescent coupling of femtosecond laser written waveguides with elliptical and circular shape. A directional tuning of the coupling properties is realized in a cubic array by tilting the elliptical waveguides. This allows to specifically pronounce diagonal coupling. In contrast, directional insensitive coupling is demonstrated in a circular waveguide array based on circular waveguides. (c) 2007 Optical Society of America.