Integrated electro-optic devices of melt-processable single-crystalline organic films

摘要

Organic electro-optic (EO) materials are the materials of choice for high speed optical modulators with modulation frequencies greater than 100 GHz. This is due to the large EO effects observed and a low material dispersion of the dielectric constant resulting in a very small velocity mismatch between the optical and electrical waves. However, the implementation of organic materials into real devices has been hindered by several factors such as an insufficient long-term thermal and photochemical stability of the widely investigated poled polymers or the lack of available structuring techniques for the inherently superior organic EO crystalline materials. Here we report on the realization of integrated organic EO single-crystalline Mach-Zehnder modulators by a recently developed melt based channel growth technique. The main fabrication concept is to grow the organic EO single-crystals from the melt directly in pre-structured and electroded waveguide channels, which were obtained by standard optical lithographic techniques and wafer bonding. By this method single crystal structure details with a size below 30 run have been achieved and the growth of single-crystalline Mach-Zehnder modulators has been successfully demonstrated, where we have chosen DAT2 (2-(3-(2-(4-dimethylaminophenyl)vinyl)-5,5-dimethylcyclohex-2-enylidene)malononitrile) as EO material. The half-wave voltage x length product determined in the DAT2 based Mach-Zehnder modulators has been found to be 78 ± 2 Vcm for TE-modes and 60 ± 1 Vcm for TM-modes at a wavelength of 1.55 urn. The accuracy and reproducibility of the process allowed also for the realization of the first EO single-crystalline microring resonator in an organic material.