High tunability and sensitivity of 1D topological photonic crystal heterostructure
Sayed Elshahat, Zain Elabdeen A. Mohamed, Mohamed Almokhtar, Cuicui Lu
Abstract
Abstract A modality to high tunability and sensing performance of a one-dimensional (1D) topological photonic crystal (PC) heterostructure is realized, based on a new mechanism through a 1D topological PC. By inserting an aqueous defect layer as a sandwich between two 1D PCs, transmittance gradually decreases with the increasing thickness of the defect layer. However, when the two layers of the topological heterostructure interface are replaced by the defect layer, the tunability and all sensing capabilities are improved, and the principle of topology is preserved. A topologically protected edge state is formed at the heterostructure interface with a highly localized electric field. For glucose sensing, high sensitivity S = 603.753 nm RIU −1 is obtained at the low detection limit of about DL = 1.22 × <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msup> <mml:mn>10</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>4</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> RIU with high-quality factor Q = <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>2.33</mml:mn> <mml:mo>×</mml:mo> <mml:mrow> <mml:msup> <mml:mn>10</mml:mn> <mml:mn>4</mml:mn> </mml:msup> </mml:mrow> </mml:math> and a high figure of merit FOM = <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>8147.814</mml:mn> </mml:math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mtext>RI</mml:mtext> </mml:mrow> <mml:mrow> <mml:msup> <mml:mrow> <mml:mtext>U</mml:mtext> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> . Besides, the transmittance can be maintained at over 99% at low and/or high glucose concentrations, due to the coupling topological edge mode between defect mode and topological edge state. An excellent platform is examined to design a topological photonic sensor. This flexible platform can be used for any type of sensor solely by replacing the interface layers with different sensor materials. Thus, our results will promote the development of 1D topological photonic devices.