NONDESTRUCTIVE METHOD FOR MEASURING THE COUPLING BETWEEN OPTICAL WAVE-GUIDES

A new method for direct measurement of the coupling coefficient betwee n parallel and identical optical waveguides is presented, The method i s based on imaging and recording the field emerging at the output face t of the device, while the excitation at the input facet is performed by illuminating it with a planar wavefront, The angle of incidence of the wavefront is scanned with respect to the input facet. A useful and simple relationship exists between the coefficients of the normal-mod es excited by this procedure and the spatial Fourier Transform of thes e modes, From this relationship, the coupling coefficients are readily deduced. Only one pair of coupled guides running from facet-to facet is required for characterization. The method is nondestructive, simple , and requires a microcomputer assisted CCD camera and minimal standar d optical equipment. The coupling coefficient of two nearby Ti indiffu sed LiNbO3 waveguides was experimentally measured by this technique an d the results were compared to those furnished by other methods.