Light-Induced Array of Three-Dimensional Waveguides in Lithium Niobate by Employing Two-Beam Interference Field

We propose a novel approach to fabricate an array of three-dimensional waveguides in lithium niobate by employing illuminations of a pair of mutually coherent or incoherent two-beam interference patterns. Adjusting periods of the patterns and the angle between the grating vectors of the two patterns, we find that arrays of square, rectangular or parallelogrammic waveguides can be created. An array of rectangular waveguides is demonstrated in an iron doped lithium niobate by the double exposures of two-beam interference patterns with different orientations. The measured index distribution and the guiding test results show that the waveguide array is successfully fabricated.