Abstract
In this work, we propose and evaluate a concept for a selective thermal emitter based on Tamm plasmons suitable for monolithic on-chip integration and fabrication by conventional complementary metal oxide semiconductor (CMOS)-compatible processes. The original design of Tamm plasmon structures features a purely one-dimensional array of layers including a Bragg mirror and a metal. The resonant field enhancement next to the metal interface corresponding to optical Tamm states leads to resonant emission at the target wavelength, which depends on the lateral dimensions of the bandgap structure. We demonstrate the application of this concept to a silicon slab structure instead of deploying extended one dimensional layers thus enabling coupling into slab waveguides. Here we focus on the mid-infrared region for absorption sensing applications, particularly on the CO2 absorption line at 4.26 µm as an example. The proposed genetic-algorithm optimization process utilizing the finite-element method and the transfer-matrix method reveals resonant absorption in case of incident modes guided by the slab and, by Kirchhoff’s law, corresponds to emittance up to 90% depending on different choices of the silicon slab height when the structure is used as a thermal emitter. Although we focus on the application as an emitter in the present work, the structure can also be operated as an absorber providing adjusted lateral dimensions and/or exchanged materials (e.g., a different choice for metal).
Highlights
Selective thermal emitters gained increased attention in recent years in context with several sensing applications [1,2,3,4,5]
A direct on-chip implementation can be realized by lateral patterning, which can be provided by complementary metal oxide semiconductor (CMOS) technologies
We model a by concepts used for designing 1D-TP structures featuring extended layers as well as concepts for applying concepts used for designing structures featuring extended layers as wellwhich as concepts optical resonators in dielectric slabs
Summary
Selective thermal emitters gained increased attention in recent years in context with several sensing applications [1,2,3,4,5]. The featured TP design provides vertical (in-plane) light-confinement by index guiding as well as lateral light-confinement by the optical TP state located at the DBR-metal interface, similar to defect cavities in photonic crystal slab structures [19]. The optical resonance (i.e., field enhancement near the dielectric-metal interface) features damping through lateral losses by coupling to modes in the slab waveguide and absorption in the metal as well as vertical losses by radiation. We show that high-Q resonances in STP-structures are possible for typical slab thicknesses used in mid IR Si slab-waveguides based on evolutionary optimization methods. The simulation of the complete waveguide-resonator-metal system implicates effective coupling between the guided mode in the Si-slab and the resonant TP mode, which enables monolithic on-chip integration of the obtained STP designs. Preliminary results of our work have been published at the conference “Eurosensors 2018” [21]
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