Direct electron beam writing of channel waveguides in nonlinear optical organic crystals.

We report on optical channel waveguiding in an organic crystalline waveguide produced by direct electron beam patterning. The refractive index profile as a function of the applied electron fluence has been determined by a reflection scan method in the nonlinear optical organic crystal 4-N, N-dimethylamino-4'-N'-methyl-stilbazolium tosylate (DAST). A maximal refractive index reduction of Deltan1 = -0.3 at a probing wave-length of 633 nm has been measured for an electron fluence of 2.6mC/cm(2). Furthermore, a new concept of direct channel waveguide patterning in bulk crystals is presented and waveguiding has been demonstrated in the produced structures by end-fire coupling. Mach-Zehnder modulators have been successfully realized and a first electro-optic modulation at a wavelength of lambda= 1.55mum has been demonstrated therein.