One-Dimensional Topological Photonic Crystal Mirror Heterostructure for Sensing

• Main Authors: Sayed Elshahat, Israa Abood, Mohamed Saleh M. Esmail, Zhengbiao Ouyang, Cuicui Lu
• Format: Article
• Language: English
• Published: MDPI AG 2021-07-01
• Series: Nanomaterials
• Subjects: topological photonic crystal; edge-state-mode; electro-optical; sensitivity; quality-factor
• Online Access: https://www.mdpi.com/2079-4991/11/8/1940

A paradigm for high-quality factor <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo stretchy="false">(</mo><mi>Q</mi></mrow></semantics></math></inline-formula>) with a substantial fulfillment for appraising sensing ability and performance has been investigated. Through constructing a 1D (one-dimensional) topological photonic crystal (PhC) mirror heterostructure, which is formed by the image view of 1D topological PhC stacking with its original one. In the 1D topological PhC-mirror heterostructure, there is an interesting mode that appeared with the symmetric, typical Lorentzian-line shape with 100% transmittance in the topological mirror edge-state mode (hybrid resonance mode) at the heterostructure interface. Physically, such a mode is a defect mode, but the defect is introduced through topological operations. The high <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>Q</mi></semantics></math></inline-formula>-factor of 5.08 × 10⁴ is obtained due to the strong optical localization of the defect mode at the topological edge area. Consequently, this device acts as a narrow passband filter. Moreover, due to the narrow bandpass property, it may be an advantageous reference for many applications in filtering, switching, and sensing. Thus, introducing an electro-optical (EO) polymer layer at the interface to modify the edge defect can tune the defect mode both in frequency and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>Q</mi></semantics></math></inline-formula>-factor for higher spatial pulse compression and higher EO sensitivity. Accordingly, the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>Q</mi></semantics></math></inline-formula>-factor of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mrow><mn>10</mn></mrow><mn>5</mn></msup><mo>,</mo></mrow></semantics></math></inline-formula> the sensitivity of 616 nm/RIU, and the figure of merit of 49,677.42 RIU⁻¹ are obtained. The sensing ability and performance are attributable to the strong optical localization in the interface region and enhanced light-matter interaction. We predict that the 1D topological PhC mirror heterostructure will be an outstanding point in the field of optical sensing, filters, and optical switching in different fields.