Infra-red spectral microscopy of standing-wave resonances in single metal-dielectric-metal thin-film cavity

Abstract

Resonantly absorbing thin films comprising periodically sub-wavelength structured metal surface, dielectric spacer, and metal ground plane are a topic of current interest with important applications. These structures are frequently described as "metamaterials", where effective permittivity and permeability with dispersion near electric and magnetic resonances allow impedance matching to free space for maximum absorption. In this paper, we compare synchrotron-based infrared spectral microscopy of a single isolated unit cell and a periodic array, and we show that the resonances have little to do with periodicity. Instead, the observed absorption spectra of usual periodically structured thin films are best described as due to standing-wave resonances within each independent unit cell, rather than as due to effective optical constants of a metamaterial. The effect of having arrays of unit cells is mainly to strengthen the absorption by increasing the fill factor, and such arrays need not be periodic. Initial work toward applying the subject absorbers to room-temperature bolometer arrays is presented.

Synchrotron-Based Three-Dimensional Fourier-Transform Infrared Spectro-Microtomography of Murchison Meteorite Grain

“…In several cases where the structure is known in advance, so that the spatial index variations are known, and where the index contrast is strong and the surfaces convoluted, IR tomography has confirmed the structure without distortion. 60,[62][63][64][65][66] This gives confidence to the application of the technique to situations such as ours, where the structure and index distribution is unknown in advance, though the index variations are expected from complementary measurements to be small.…”

Modes Coupling Analysis of Surface Plasmon Polaritons Based Resonance Manipulation in Infrared Metamaterial Absorber

“…Since the concept of SPPs was proposed, increasing researches have been carried out to explore how to excite and manipulate SPPs efficiently. Recently, resonant metamaterial absorbers featured by metal-dielectric-metal sandwich structures, have become one of the main resources to manipulate SPPs with different periodic patterns such as one-dimensional (1D) grating 7 8 9 10 , 2D disk arrays 11 12 , patch arrays 13 , cross bars 14 and aperiodic patterns such as nanoparticles 15 and single cavity 16 . The interactions between SPPs and other kinds of resonances, e.g.…”

“…As for the sandwich structure absorbers decorated by surface patterns, once SPPs on the dielectric-metal surface is excited, SPPs on the upper and lower dielectric-metal interfaces may be coupled and further complicated by the discontinuity of the upper interface patterns. On the other hand, standing waves have been introduced to explain the electromagnetic scattering problems of the metal-insulator-metal infrared absorber 16 27 28 . In this paper, we focus on standing waves between the upper metallic grating and the lower metallic base.…”

Effect of Compound Dielectric and Metal Thinning on Metal-Insulator-Metal Resonant Absorbers for Multispectral Infrared Air-Bridge Bolometers

“…Thus, the absorption spectrum is due mainly to the geometry of the single unit cell (dimensions l and t) and the refractive index n of the dielectric. An array of stripes merely increases the fill factor and the total absorption [9]. Non-uniformity of the parameter l, as occurs near the edges of the actual device in Fig.…”