Characterization and performance evaluation of coupled multiwaveguide arrays

A new and effective nonintrusive method for characterization of N coupled waveguides is presented. The method is able to furnish readily the coupling parameters, of most significance, and furnishes in addition, a way of assessment of overall device quality and performance. The procedure is based on a semi-empirical implementation of coupled mode theory, by means of which different functions are defined for different input configurations. In a well-functioning device, all these function should attain a common single minimum, out of which the coupling coefficient and additional parameters of the device are deduced. Devices were fabricated on Z-cut LiNbO₃ crystals by in-diffusion of Titanium. The method was applied in order to measure the wavelength and polarization dependence of the coupling coefficient.