Refractive index control and waveguide fabrication of DAST crystals by photobleaching technique

We report on the optical waveguide fabrication of organic ionic crystal, 4-(4-dimethylaminostyryl)-1-methylpyridinium tosylate (DAST), a promising material for electro-optic devices. A photobleaching technique was used to control the refractive index of DAST crystals. The change of refractive index as well as photobleached depth were evaluated by a prism-coupler and the values were compared with the results calculated from diffraction efficiency of refractive index grating. We fabricated a multimode waveguide using a Xe lamp with a mask covered on the crystal and the propagation loss of the waveguide was evaluated at 1.3 μm wavelength.