Rainbow Trapping in Hyperbolic Metamaterial Waveguide

Abstract

The recent reported trapped ''rainbow'' storage of light using metamaterials and plasmonic graded surface gratings has generated considerable interest for on-chip slow light. The potential for controlling the velocity of broadband light in guided photonic structures opens up tremendous opportunities to manipulate light for optical modulation, switching, communication and light-matter interactions. However, previously reported designs for rainbow trapping are generally constrained by inherent difficulties resulting in the limited experimental realization of this intriguing effect. Here we propose a hyperbolic metamaterial structure to realize a highly efficient rainbow trapping effect, which, importantly, is not limited by those severe theoretical constraints required in previously reported insulator-negative-index-insulator, insulator-metal-insulator and metal-insulator-metal waveguide tapers, and therefore representing a significant promise to realize the rainbow trapping structure practically. S low-light chips are believed to be promising for enhanced optical buffering, signal processing, and enhanced nonlinear optics. Unfortunately, the observation of slow light in conventional schemes based on BoseEinstein condensates 1 or atomic vapors 2 imposes severe constraints in experimental conditions, including narrow bandwidth, limited working wavelengths and strong temperature dependence. The slowed modes are difficult to be implemented into other materials or devices to develop practical applications. Consequently, solidstate nanophotonic structures that can achieve the slow light effect under room temperature are of particular interest [3][4][5] . Recent theoretical and experimental investigations on the ''trapped rainbow'' storage of light waves in metamaterials 6 and plasmonic structures 7-10 have generated considerable interest since various solid-state materials can be introduced in the design of nanostructures to trap electromagnetic (EM) modes. With the ability to produce highly confined and localized optical fields, it is believed that the conventional rules for light-matter interactions need to be re-examined, and new regimes of optical physics are expected. To develop applications based on this intriguing broadband slow light effect, various architectures have been proposed, including surface graded metallic gratings 9,10 , insulator-negative-index-insulator (INI) 6,11 , insulator-metal-insulator (IMI) 12 and metal-insulator-metal (MIM) waveguide tapers [13][14][15] . However, each proposal has its inherent difficulties resulting in the limited experimental realization of the rainbow trapping structures. For example, in our previous experimental reports, white light surface plasmon polariton (SPP) modes were launched into the on-chip gratings through nanoslits 9,10 , leading to a very weak total coupling efficiency. For INI waveguide tapers, there is currently no clear pathway for realizing materials with negative refractive indices over a broad spectral range 6 . In a recent theoretical investigation...

Visible-near infrared ultra-broadband polarization-independent metamaterial perfect absorber involving phase-change materials

“…As the electric and magnetic resonant frequencies of MMPAs are determined by their geometry, the conventional MMPAs can only produce certain electric and magnetic resonances at the specific wavelengths [13], which restricts their practical applications. For this, several schemes concentrating on dual-band absorption [14][15][16], multiband absorption [17,18], and broadband light absorption at terahertz frequencies [19][20][21][22][23][24] generated by MMPAs have been demonstrated, which are more conducive to high-integration optoelectronic applications. For instance, Cui et al [21] have demonstrated an ultra-broadband thin-film infrared absorber made of saw-toothed anisotropic metamaterial by etching an MM slab into a sawtooth shape with the tooth widths increasing gradually from top to bottom.…”

“…For instance, Cui et al [21] have demonstrated an ultra-broadband thin-film infrared absorber made of saw-toothed anisotropic metamaterial by etching an MM slab into a sawtooth shape with the tooth widths increasing gradually from top to bottom. In another example, Hu et al [24] reported that the trapping "rainbow" storage of light with metamaterials and plasmonic graded surface gratings produces broadband light absorption by controlling the velocity of light in guided photonic structures. Nevertheless, these structures inevitably become increasingly complex when two or more sub-resonators operating at different wavelengths are compacted in a composite unit cell for the multispectral absorption, which limits practical device applications.…”

Transmission and absorption in a waveguide with a metamaterial cavity

“…We remark that the current problem has an analogue in electromagnetic setting for TMpolarised waves in two-dimensional waveguide with perfectly-electric conducting surfaces in which µ represents the effect of a dielectric 18,19 . In accordance with the use of a continuum model (6) to describe the microstructure of the array, the terraced upper boundary of the metamaterial cavity illustrated in Fig.…”

Efficient, broadband and wide-angle hot-electron transduction using metal-semiconductor hyperbolic metamaterials

“…We find that despite a 20 % fluctuations in the metal thickness, both homogeneous and inhomogeneous (discussed below) HMM devices exhibit only a small shift in the absorption spectrum (< 5 %) with the absorptance being essentially unchanged, within the spectral range of interest (1 eV-1.5 eV). The linear/tapered air trenches can be produced by advanced lithographic methods, including electron beam lithography, laser beam direct writing, and focused ion beam milling/lithography/direct deposition [2]- [5], [37]- [39]. The vertical interconnect technology, as a mature process in integrated circuits (ICs), may be used to connect different superlattices for collecting hot electrons to loading circuit.…”