1 July 2004 Silicon-based near-infrared tunable filters based on liquid crystals
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Abstract
Complementary metal-oxide-semiconductor-compatible tunable Fabry-Perot microcavities filled with liquid crystals (LCs) were realized and studied in the near-infrared region. The microcavities were produced by chip bonding technique, which allows one to infill LC between two [SiO2/Si]n λ/4 (λ = 1.5 μm) Dielectric Bragg Reflectors separated by 950 nm thick SiO2 posts. The Dielectric Bragg reflectors were realized on Si or SiO2 substrates Liquid crystals with positive and negative dielectric anisotropy were used, i.e. MerckE7 (Δε=13.8) and Merck-6608 LC (Δε=-4.2). Mirror-integrated electrodes allow an external bias to induce an electrical field and to tune the LC properties and, hence, the microcavity resonance. Electric-field-induced shifts of the second-order cavity modes of ~120 nm and ~50 nm were obtained for Merck-E7 and Merck-6608 LC, with driving potentials of 5 V and 10 V, respectively. The transmittance at the cavity resonance is typically in the order of 10%. Simulation of cavities allows to identify surface roughness of the Dielectric-Bragg-Reflectors as the major origin of the transmission losses. The switching behavior of microcavities filled with E7 were studied as function of applied fields. Both switch-on ton and switch-off toff times were measured and were found to be lower than 5 ms.
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Alberto Mezzetti, Georg Pucker, Michele Crivellari, Constantinos Kompocholis, Pierluigi Bellutti, Alberto Lui, Nicola Daldosso, Francesco Riboli, Massimo Saiani, Zeno Gaburro, Lorenzo Pavesi, "Silicon-based near-infrared tunable filters based on liquid crystals", Proc. SPIE 5357, Optoelectronic Integration on Silicon, (1 July 2004); doi: 10.1117/12.527762; https://doi.org/10.1117/12.527762
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