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Linear and non-linear optical properties[1] of liquid crystals (LC) make them extremely appealing for use in a wide range of different optoelectronic applications other than displays. Their high optical anisotropy (in some cases higher than 0.2) implies large phase shifts in very short optical paths. Furthermore, their strong electro-optic effect allows rapid reorientation of their optical axis with indeed very low voltages in the range of only a few volt and hence compatible with current silicon technology. In particular, this last property makes them very attractive for low power consumption photonic applications. In this communication, light polarization dependence of channel waveguides made of SiO2/Si grooves filled with the commercial nematic liquid crystal E7 is shown. Grooves were obtained by initially wet etching phosphorous-doped (1 0 0) silicon substrates and then by thermally growing SiO2 up to a thickness of about 2 μm[2]. The cross section of the groove resulted with this method was of trapezoidal shape due to the preferential etching plane of silicon at 54.7° with respect to the wafer plane. The upper width of the groove as defined from the lithographic mask was 10 μm. The processed silicon substrate was subsequently assembled into a typical LC cell with a sodalime glass plate on the top. The inner surface of the glass had been previously spin-coated with Nylon 6, which was then rubbed for the alignment of the LC molecules approximately along the grooves. Propagation of infrared laser light (1550 nm) launched at one end of the waveguide by butt coupling was observed for a channel length of 2 cm. The signal at the output of the …
University of Ghent
Publication date: 
1 Jan 2006

Domenico Donisi, Bob Bellini, Rita Asquini, Romeo Beccherelli, Antonio D'Alessandro

Biblio References: 
Pages: O17
International Workshop on Liquid Crystals for Photonics