Miniaturized electro-optical modulator based on substrate-free thin films

We report on an integrable electro-optic modulator (EOM), exploiting the advantages of substrate-free thin film technology to achieve a small device footprint of less than 30µm along the beam propagation direction. By integrating an electrooptically active layer into a resonant Fabry-Perot (FP) structure with dielectric thin film mirrors, an EOM, which modulates the transmitted amplitude, is manufactured and characterized. We show results on electro-optically active polymers as the FP cavity material, which have revealed an electro-optic coefficient in the three-digit pm/V range at a wavelength of 980nm. Furthermore, we analyze the applicability of piezoelectric zinc oxide (ZnO) as the active layer material, which exhibits high transmission in the visible wavelength region. Fabrication of ZnO using magnetron sputtering under oblique angle deposition conditions has the potential to produce porous, inclined, crystalline thin films with an enhanced piezoelectric coefficient d₃₃, which is otherwise only found in bulk ceramics like lead zirconate titanate. The use of such nanostructured ZnO thin films with an improved electro-mechanical coupling as active cavity layer fosters improved modulation while consuming less energy.