Topological Engineering of Interfacial Optical Tamm States for Highly Sensitive Near-Singular-Phase Optical Detection

Abstract

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...

Engineering a Full Gamut of Structural Colors in All-Dielectric Mesoporous Network Metamaterials

“…The predictions of the reflectance spectra of mesoporous metamaterial samples were done by using the semi-analytical transfer matrix method 59,60 ( Supplementary Fig. S5).…”

Sensitive singular-phase optical detection without phase measurements with Tamm plasmons

“…1b, blue line). The choice of the operational wavelength is arbitrary, and the resonance can be easily tuned across the visible and infrared spectral ranges by adjusting the parameters of the structure (i.e., layer thicknesses or materials) [37]. Unlike surface plasmon polariton modes that are p-polarized, Tamm plasmon modes can be excited by incident waves of both orthogonal s-and p-polarizations [21,22].…”

“…We have recently demonstrated that perfect Tamm absorbers can be designed by conjugate impedance matching finite-size 1D photonic crystals and metal surfaces [37]. Below their plasma frequency, metal surfaces are characterized by predominantly reactive impedances (i.e., with { } > { }).…”

“…1b. We would like to emphasize that formation of the interfacial Tamm plasmon states does not require periodicity in the medium, and can be achieved in completely aperiodic structures [22,37]. A 1D periodic PhC was chosen here to illustrate the conjugate-matching mechanism of the Tamm state formation owing to its well-studied geometry and known spectral characteristics.…”

“…In turn, the sensor sensitivity maximizes as the angle approaches that of normal incidence, and reduces dramatically at oblique angles. Note that if the sensor is optimized to exhibit complete absorption for one polarization of incident light at a larger angle of incidence [37], the resonant spectral feature in the amplitude ellipsometric angle spectrum becomes symmetrical, and the amplitude-detection sensitivity is reduced. It should be noted that phase measurements could further increase the sensitivity of the Tamm sensor, as illustrated in Fig.…”