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Abstract
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In this work, behavior of defect mode in one-dimensional ternary photonic crystal (1DTPC)
structure with arrangement of (MgF2/Ag/TiO2)5LiNbO3(TiO2/Ag/MgF2)5 was investigated under the
applied external electric dc voltage. The defect layer is lithium niobate (LiNbO3), an electro-optical (EO)
material whose refractive index is voltage-dependent with high EO coefficient. In comparison, magnesium
fluoride (MgF2) and titanium dioxide (TiO2) layers have very low EO coefficients. A narrow localized
defect mode with perfect transmittance was appeared inside the photonic band gap. Under applying the
positive or negative biases, red shift and blue shift was observed in the defect mode, respectively. More
than 120 nm tunability was obtained under externally applied voltage in the range of −200 V to 200 V. The
physical interpretation is very simple. Change in optical path-length displaces the localized wavelength of
the defect mode due to Bragg interface condition. The externally tunable localized mode can be employed
in designing a controllable optical filter, one of the essential devices for new-generation all-optical integrated
circuits.
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