Abstract

The titanium-indiffused proton-exchange (TIPE) method has been shown to be very effective in the fabrication of lenses on planar Ti:LiNbO₃ waveguides. It should also be useful for the fabrication of gratings and other passive components. The characteristics of these components are determined by the index indifference between the planar titanium-indiffused region and the TIPE region. It is, therefore, of interest to have a direct method for measuring this difference and thereby being able to characterize the TIPE process in terms of the fabrication parameters such as exchange time, exchange temperature, and degree of buffering of the exchange solution. The method we have developed for directly measuring the TIPE index change consists of forming an isosceles triangle by the TIPE process and directing a wide collimated guided wave into the triangle perpendicular to the base. The two halves of the beam are refracted toward the symmetry line of the triangle and intersect, forming a fringe pattern outside the waveguide. The fringe spacing and, therefore, the index difference can be measured with an accuracy of ~0.1%.

© 1987 Optical Society of America