Eur. Phys. J. D (2015) 69: 221
https://doi.org/10.1140/epjd/e2015-60283-4

Regular Article

Tuning the defect mode in ternary photonic crystal with external voltage for designing a controllable optical filter

¹ Department of Physics, Azarbaijan Shahid Madani University, Tabriz, Iran
² Department of Physics, Tabriz Branch, Islamic Azad University, Tabriz, Iran

^a e-mail: k-jamshidi@azaruniv.ac.ir

Received: 11 May 2015
Received in final form: 28 June 2015
Published online: 24 September 2015

Abstract

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.