High-sensitivity terahertz sensor based on Tamm plasmon polaritons of a graphene asymmetric structure

Abstract

A new asymmetric structure based on Tamm plasmon polaritons (TPPs) and a metal-distributed Bragg reflector (DBR) is proposed in this paper, which can be applied in high-sensitivity terahertz sensors. The structure includes monolayer graphene and two DBRs with different central frequencies on two sides of the graphene. One of its edge faces is introduced by silver film for enhancing the TPPs excitation. The result shows two Tamm plasmonic modes at frequencies of 1.0 THz and 1.1 THz can be excited by the structure. By increasing Fermi energy of graphene, or reducing the width of the top defect layer, the TPPs excitation can be enhanced, and the sensitivity of the structure can also be improved. Moreover, the sensitivity is more sensitive to the incidence angle of TM and TE polarizations from 0° to 25°. By optimizing the structural parameters, the sensitivity and figure of merit of two Tamm plasmonic modes can attain 1.17 THz/RIU, 1.2 THz/RIU, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>32.28</mml:mn> </mml:mrow> <mml:mspace width="thickmathspace"/> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:msup> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">R</mml:mi> <mml:mi mathvariant="normal">I</mml:mi> <mml:mi mathvariant="normal">U</mml:mi> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> , and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>30.95</mml:mn> </mml:mrow> <mml:mspace width="thickmathspace"/> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:msup> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">R</mml:mi> <mml:mi mathvariant="normal">I</mml:mi> <mml:mi mathvariant="normal">U</mml:mi> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> , respectively, which demonstrates that such a structure is a candidate for a dynamic tunable TPPs terahertz device for a high-sensitivity terahertz sensor.