Simulation and Fabrication of Two Dimensional Nonlinear Photonic Crystals using Barium Titanate Thin Films
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1014-AA07-07
Simulation and Fabrication of Two Dimensional Nonlinear Photonic Crystals using Barium Titanate Thin Films Pao Tai Lin, Zhifu Liu, and Bruce W. Wessels Material Science & Engineering, Northwestern University, 2220 Campus Drive, Evanston, IL, 60208-3108
ABSTRACT Photonic crystal (PhC) can potentially result in enhanced optical properties around critical points in the photonic band gap. Of interest here are enhanced nonlinear optical effects. In this study, one and two dimensional nonlinear PhC were designed and fabricated using barium titanium oxide (BTO) thin films as the active medium. Nonlinear PhC made with barium titanate thin films potentially provide integrated devices with the advantages of wide tunability and high stability. Films 500 nm thick deposited on MgO substrates were utilized. Two dimensional PhC structures were defined by focused ion beams (FIB). Before patterning, a thin metal layer was deposited on the barium titanate layers in order to improve the conductivity of the samples. After writing the patterns, cylindrical air holes were generated in the thin film layers. The PhC lattice constant and the hole radius were selected in sub-micron region in order to satisfy the requirement of wave resonance. The PhCs with sub-micron features were characterized by the atomic force microscopy (AFM), scanning electron microscopy (SEM), and near field optical microscopy (NSOM). The transmission spectra of the PhC waveguides were calculated with a continuous wide band source that covered 1 to 2 micron wavelength. Simulations of the transmission characteristics were performed using the two dimensional finite difference time domain method (FDTD). INTRODUCTION Devices utilizing photonic crystals have attracted much attention due to their potential in integrated optics [1,2]. Photonic crystals are candidates for compact slow light devices [3,4], low threshold lasers [5], low Vπ electro-optic modulators [6], high Q microcavities [7], and microelectromechanical actuators [8]. In order to achieve wide tunability and high speed PhC devices, non-linear optical materials have been proposed. Enhancement of non-linear optical effects in PhC has been predicted. Ferroelectric oxides such as lithium niobate, lead lanthanum zirconate titanate, and barium titanate are especially promising since they have large electrooptic optic coefficients and short response time [9,10]. Simulation of ferroelectric PhC, such as the temporal modulation based on the Pockels effect and tunable multichannel filters, were previously performed [11,12]. In the case of a temporal modulation of PhC, new side bands are generated by an external electric field. The interval between the new side bands and the original band is the same as the modulation frequency of the applied field. Furthermore, optical tunable multichannel filters are achieved by an optical non-linearity. For example, a 90 nm channel shift can be induced by a 75 MW/cm2 pump light, where this high intensity pump light serves as the control signal [12].
In this paper, the
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