Radiative decay engineering 7: Tamm state-coupled emission using a hybrid plasmonic–photonic structure

Abstract

There is a continuing need to increase the brightness and photostability of fluorophores for use in biotechnology, medical diagnostics and cell imaging. One approach developed during the past decade is to use metallic surfaces and nanostructures. It is now known that excited state fluorophores display interactions with surface plasmons, which can increase the radiative decay rates, modify the spatial distribution of emission and result in directional emission. One important example is Surface Plasmon-Coupled Emission (SPCE). In this phenomenon the fluorophores at close distances from a thin metal film, typically silver, display emission over a small range of angles into the substrate. A disadvantage of SPCE is that the emission occur at large angles relative to the surface normal, and at angles which are larger than the critical angle for the glass substrate. The large angles make it difficult to collect all the coupled emission and have prevented use of SPCE with high-throughput and/or array applications. In the present report we describe a simple multi-layer metal-dielectric structure which allows excitation with light that is perpendicular (normal) to the plane and provides emission within a narrow angular distribution that is normal to the plane. This structure consist of a thin silver film on top of a multi-layer dielectric Bragg grating, with no nanoscale features except for the metal or dielectric layer thicknesses. Our structure is designed to support optical Tamm states, which are trapped electromagnetic modes between the metal film and the underlying Bragg grating. We used simulations with the transfer matrix method to understand the optical properties of Tamm states and localization of the modes or electric fields in the structure. Tamm states can exist with zero in-plane wavevector components and can be created without the use of a coupling prism. We show that fluorophores on top of the metal film can interact with the Tamm state under the metal film and display Tamm state-coupled emission (TSCE). In contrast to SPCE, the Tamm states can display either S- or P-polarization. The TSCE angle is highly sensitive to wavelength which suggests the use of Tamm structures to provide both directional emission and wavelength dispersion. Metallic structures can modify fluorophore decay rates but also have high losses. Photonic crystals have low losses, but may lack the enhanced light-induced fields near metals. The combination of plasmonic and photonic structures offers the opportunity for radiative decay engineering to design new formats for clinical testing and other fluorescence-based applications.

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

“…Coupling of incident light to the optical Tamm state can be optimized via structure design to result in perfect absorption (i.e., zero reflection) at a given frequency 36 . These attractive characteristics of the optical Tamm structures already led to a variety of their applications in optoelectronics and photonics, including amplitude-based optical sensing 32,37,38 , development of metal/semiconductor lasers [39][40][41] , etc. [42][43][44][45][46][47][48][49] .…”

Polarization-Controlled Confined Tamm Plasmon Lasers

“…TPs have been proposed and demonstrated as a novel straightforward and promising tool to engineer fluorophores emission in terms of directionality, wavelength and decay rates. [33][34][35] TPs combined with mesoporous DBR have been proven to be successfully employed as highsensitivity sensors in alternative to surface plasmons. 36 In addition, the coexistence of Tamm plasmon and surface plasmon modes in these hybrid metal/dielectric structures 37,38 could make of Tamm plasmon lasers a new approach for the development of novel efficient surface plasmon sources.…”

Directing Fluorescence with Plasmonic and Photonic Structures

“…Moreover, the wavevector of Tamm–plasmons is smaller than that of light in vacuum, so it can be directly excited from air without the aid of prisms or gratings. 17,18 …”