Fabrication of nonlinear optical waveguide

A ridge waveguide of an organic salt, 4-(4-dimethylaminostyryl)-1-methylpyridinium tosylate, DAST, which has the largest second-order optical nonlinearities, was fabricated for the first time to our knowledge. The DAST crystal was covered by poly (methylmethacrylate) as a protective layer for a photo-resist solution, then standard photolithography and oxygen reactive ion etching (RIE) processes were applied. The DAST ridge waveguide, 34 x 20 mum and 6 x 6 mum channels with 2 mm in length were successfully fabricated by this process. For the DAST crystal, photo bleaching process was effectively applied to reduce the refractive index of the crystal that can be applied to fabricate a cladding layer for the ridge waveguide. Fabrication of serially grafted waveguide of the DAST and UV cured resin was also tried that is important technology for actual application of the crystal waveguide.