Enhancing Tamm Plasmon Sensor Performance Using Nanostructured Gold Grating and Porous Materials

Abstract

In this article, we introduce a gas sensor concept consisting of a nanostructured gold grating coupled with a distributed Bragg reflector (DBR). This coupling makes it possible to obtain plasmonic Tamm states, where excitation is possible at normal incidence and does not require the use of the Kretschmann configuration. Through parameters optimization of the gold nanostructured grating, we achieved well-defined and localized Tamm resonances between the gold nanostructured grating and the distributed Bragg reflector composed of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$ \text {SiO}_{{2}}/\text {Si}_{{3}}\text {N}_{{4}}$ </tex-math></inline-formula>. To exploit the spatial confinement of the energy of the Tamm states in order to measure the change in refractive index, we propose three configurations, in which we substitute the last nitride layer in the Bragg reflector with porous materials. In the first configuration, we use a porous nitride portion with 30% porosity, producing sensitivity <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${S} = {170}~\text {nm}/\text {RIU}$ </tex-math></inline-formula> and figure of merit <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text {FOM} = 27.1~\text {RIU}^{-{1}}$ </tex-math></inline-formula>. In the second configuration, we use a porous nitride layer with a porosity of 30% (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${S} = {175}~\text {nm}/\text {RIU}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text {FOM} = {27.3}~\text {RIU}^{-{1}}$ </tex-math></inline-formula>). Finally, the third configuration adopts a 66% porous silicon layer (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${S} = {268}~\text {nm}/\text {RIU}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text {FOM} = {43.6}~\text {RIU}^{-{1}}$ </tex-math></inline-formula>). These values show the significant potential for sensing applications.