Topological engineering of interfacial optical Tamm states for highly-sensitive near-singular-phase optical detection

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.Comment: 31 pages; 6 main text figures and 10 supplementary figure

Theoretical and experimental study of temperature-dependent spectral properties of multi-layer metal-dielectric nano-film structures

ABSTRACT We investigate theoretically and experimentally frequency-selective transmission and reflection characteristics of thin-film metal-dielectric multi-layer structures. The thin-film structures were deposited on glass substrates using a thermal evaporation technique, and their optical characteristics were studied in the visible and infrared frequency bands. A computational scheme based on a reiterative method for the calculation of reflection from a multi-layer stack is developed to model interference filters, polarization splitters and surface-plasmon sensors and also to study the effect of temperature change on the device characteristics. The temperature dependence is introduced in the model by taking into account the thermo-optic effect in the dielectrics and contributions from the phonon-electron and electron-electron scattering in metal layers. Detailed analysis of reflectance characteristics of thin-film stacks of various material compositions has been performed with the aim to estimate their temperature sensitivity, to achieve improved device performance and to design sensors and tunable filters