Optical waveguides and integrated electro-optic modulators based on highly-efficient organic nonlinear optical crystal OH1

We have recently developed a very promising organic crystal OH1 (2-(3-(4-hydroxystyryl)-5,5-dimethyl- cyclohex-2-enylidene)malononitrile). OH1 presents excellent electro-optic properties reaching electro-optic figures of merit as large as in the state-of-the-art organic salt DAST. Additionally, the processing possibilities of OH1 are considerably improved compared to DAST. We have developed an epitaxial solution growth technique that allows reproducible fabrication of high-quality OH1 films with large-area single- crystalline domains of more than 2 cm2 and thickness between 0.1 and 4 Icircfrac14, which is of particular importance for integrated optics. Using a specially developed photolithographic process, we have fabricated wire single-crystalline optical waveguides of OH1 on glass substrates, as shown in Fig. In these waveguides, phase electro-optic modulation with high in-device figures of merit has been demonstrated, i.e. half- wave voltage x interaction length product V_piL of 8.4 Vcm and 28 Vcm at 632.8 nm and 852 nm, respectively. With an optimized electrode configuration with smaller (1 Icircfrac14m) spacing between the electrodes and the waveguide,V_piL will be reduced from 8.4 Vcm, as obtained in our device, to 0.3 Vcm in the optimized case. This allows for the fabrication of sub-l-V half-wave voltage, organic electro-optic modulators with highly stable chromophore orientation.