All-Optical Plasmonic Switches Based on Asymmetric Directional Couplers Incorporating Bragg Gratings
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All-Optical Plasmonic Switches Based on Asymmetric Directional Couplers Incorporating Bragg Gratings Shiva Khani 1 & Mohammad Danaie 1
&
Pejman Rezaei 1
Received: 6 August 2019 / Accepted: 16 December 2019 # Springer Science+Business Media, LLC, part of Springer Nature 2019
Abstract In this paper, a novel technique for realization of all-optical plasmonic switches is presented. The proposed structure is based on an asymmetric metal-insulator-metal plasmonic directional coupler. A Bragg grating is used on one of the directional coupler’s adjacent waveguides while the other remains intact. Such a modification results in dissimilar input-output transmission spectrums for each of the two input ports. The Bragg grating creates a bandgap region in one of the signal paths while the other path has no bandgap. The directional coupler is filled with a dielectric with high Kerr-type nonlinearity. One of the input ports is used for the data signal and the other port for the control (pump) signal. When the pump signal is present, a small modification in the refractive index of the Kerr material occurs which slightly changes the bandgap region. The input signal’s wavelength is chosen at the bandgap edge so that it can only pass through the structure when the control signal is present. The structure proposed in this paper is numerically simulated using finite difference time domain method. Silver and Ag/BaO composite are used as the metal and dielectric materials. Since the proposed topology incorporates two different input ports for the control and data signals, it has the potential to be used in complex-integrated optical circuits. Keywords Surface plasmons . All-optical switches . Kerr effect . Metal-dielectric-metal waveguides . Directional coupler . Bragg grating . Transmission line method
Introduction Plasmonic structures due to employing surface plasmon polaritons (SPPs) at metal-dielectric interfaces are harbingers of combining electronic and photonic circuits on a single platform. SPPs can guide light at deep subwavelength scales [1]. As a result, plasmonic structure dimensions can be reduced smaller than the incident wavelength. In contrary, other photonic platforms such as photonic crystals or Si photonic devices [2–6] do not have this property and result in much larger dimensions. Consequently, plasmonic devices seem to play an important role in integrated photonic sensors. Over the past few years, various types of metal-dielectric-metal (MDM) plasmonic structures including optical filters [7–9], sensors [10, 11], demultiplexers [12, 13], splitters [14], directional couplers (DCs) [15], slow lights [16], and switches have been designed
* Mohammad Danaie [email protected] 1
Faculty of Electrical and Computer Engineering, Semnan University, Semnan, Iran
and implemented. Among these structures, optical filters [17, 18] have been used as a basis to design other more complex structures. Integration of MDM configurations and other electronic or microwave components [19–23] seems to be the most desirable feature of
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