Abstract:We developed planar multilayered photonic-plasmonic structures, which support topologically protected optical states on the interface between metal and dielectric materials, known as optical Tamm states. Coupling of incident light to the Tamm states can result in perfect absorption within one of several narrow frequency bands, which is accompanied by a singular behavior of the phase of electromagnetic field. In the case of near-perfect absorptance, very fast local variation of the phase can still be engineered. In this work, we theoretically and experimentally demonstrate how these drastic phase changes can improve sensitivity of optical sensors. A planar Tamm absorber was fabricated and used to demonstrate remote near-singular-phase temperature sensing with an over an order of magnitude improvement in sensor sensitivity and over two orders of magnitude improvement in the figure of merit over the standard approach of measuring shifts of resonant features in the reflectance spectra of the same absorber. Our experimentally demonstrated phase-to-amplitude detection sensitivity improvement nearly doubles that of state-of-the-art nano-patterned plasmonic singular-phase detectors, with further improvements possible via more precise fabrication. Tamm perfect absorbers form the basis for robust planar sensing platforms with tunable spectral characteristics, which do not rely on low-throughput nano-patterning techniques.Keywords: Tamm plasmons, surface modes, photonic crystals, optical impedance, geometrical phase, singular phase detection, bio(chemical) and temperature sensing Optical transduction is a widely used detection mechanism in remote sensing and monitoring of a variety of physical, chemical, and biological events. It is based on measuring environmental changes by detecting the change in one of the characteristics of light interacting with the target medium, including its amplitude, wavelength, incident angle, and phase. Optical sensing is intrinsically non-invasive, and can be used in extreme conditions, such as high toxicity, high temperatures, electrical noises, or strong magnetic fields. Among many types of optical sensors, surface-plasmon polariton (SPP) sensors are widely investigated and used [1][2][3][4][5][6][7] . Evanescent fields of SPP modes supported by metallic structures strongly interact with the surrounding dielectric medium, and environmentally-induced changes of their propagation constants provide an optical transduction mechanism 4 . Excitation of localized SPP modes generates strong electromagnetic field in a small volume close to the metal-dielectric interface, making possible detection of very small variations of the local refractive index. Hence, the SPP sensors offer highly-sensitive, label-free, and non-destructive optical detection and monitoring of chemical and 2 biological reactions on the surface. A common scheme of the SPP excitation on planar interfaces is the Kretschmann−Raether scheme, where a prism is placed on top of the metal film to excite surface plasmon polarito...
