Self-Assembled Tunable Photonic Hyper-Crystals

Abstract

We demonstrate a novel artificial optical material, the ''photonic hyper-crystal'', which combines the most interesting features of hyperbolic metamaterials and photonic crystals. Similar to hyperbolic metamaterials, photonic hyper-crystals exhibit broadband divergence in their photonic density of states due to the lack of usual diffraction limit on the photon wave vector. On the other hand, similar to photonic crystals, hyperbolic dispersion law of extraordinary photons is modulated by forbidden gaps near the boundaries of photonic Brillouin zones. Three dimensional self-assembly of photonic hyper-crystals has been achieved by application of external magnetic field to a cobalt nanoparticle-based ferrofluid. Unique spectral properties of photonic hyper-crystals lead to extreme sensitivity of the material to monolayer coatings of cobalt nanoparticles, which should find numerous applications in biological and chemical sensing. Over the last few decades a considerable progress has been made in developing artificial optical materials with novel and often counterintuitive properties. Revolutionary research by Yablonovitch and John on photonic crystals 1,2 was followed by the development of electromagnetic metamaterial paradigm by Pendry 3 . Even though considerable difficulties still exist in fabrication of three-dimensional (3D) photonic crystals and metamaterials, both fields exhibit considerable experimental progress 4,5 . On the other hand, on the theoretical side these fields are believed to be complementary but mutually exclusive. Photonic crystal effects typically occur in artificial optical media which are periodically structured on the scale of free space light wavelength l, while electromagnetic metamaterials are required to be structured (not necessarily in a periodic fashion) on the scale, which is much smaller than the free space wavelength of light. For example, in metal nanowire-based hyperbolic metamaterials 6 schematically shown in Fig. 1A the inter-wire distance must be much smaller than l. Here we report experimental realization of 3D ''photonic hyper-crystals'' which bridge this divide by combining the most interesting properties of hyperbolic metamaterials and photonic crystals.Our concept of the photonic hyper-crystal 7 is based on the fact that dispersion law of extraordinary photons in hyperbolic metamaterials does not exhibit the usual diffraction limit. In such uniaxial metamaterials the in-plane e xy and out-of-plane e z components of the dielectric permittivity tensor have opposite signs (e.g. the metal wire array hyperbolic metamaterial shown in Fig. 1A may have e z , 0 and e xy . 0 8 ), so that the photon wave vector components k i are not bounded at a given frequency of light v. Existence of large k-vector modes in a broad range of frequencies is responsible for such unusual effects as hyperlens-based super-resolution imaging [8][9][10][11] and broadband divergence of photonic density of states in hyperbolic metamaterials 12 . On the other hand, this also means that periodic modulation ...

Nonlinear optics of photonic hyper-crystals: optical limiting and hyper-computing

“…Therefore, photonic hyper-crystals exhibit light localization on deep subwavelength scales, which far exceeds the demonstrated mode volume reduction in photonic crystals. It was suggested that such strong field localization would lead to considerable enhancement of nonlinear optical effects in photonic hyper-crystals [3]. In this paper we will demonstrate that the level of nonlinearities achievable in photonic hyper-crystals indeed looks very promising for optical limiting and optical computing applications.…”

“…Strong Bragg scattering is observed near the Brillouin zone boundaries at k z ~ /L >> , leading to the formation of photonic bandgaps in both the wavenumber and the frequency domains. An example of the band structure calculations and a Bloch mode profile for a linear photonic hyper-crystal may be found in [3].…”

“…A photonic crystalbased nanocavity design enables an ultra-small mode volume, so that considerable nonlinearities may be observed even at single-photon levels. This recent success motivates us to look at the nonlinear optics of photonic hyper-crystals [3], which combine the most interesting features of hyperbolic metamaterials and photonic crystals. Photonic hypercrystals are formed by periodic modulation of hyperbolic metamaterial properties on a scale L, which is much smaller than the free space light wavelength λ.…”

Photonic Hypercrystals

“…It is this type of hyperbolic media that holds the most promise for practical applications of the concept of the hypercrystal [54].…”

Nonlinear, tunable, and active optical metasurface with liquid film

“…Prominent examples include light-induced collective orientation of liquid crystal molecules [31], pressure induced control of lasing frequency in a 1D array of droplets [32], magnetic induced ferrofluid-based hyperbolic metamaterial [33], and chemical composition induced changes enabling lasing frequency tuning in 1D systems [34] and in 2D photonic crystals [35]. Furthermore, recent studies introduced a novel interaction between SPPs and a thin liquid dielectric (TLD) film due to geometrical changes of the gas-fluid (or fluid-fluid) interface, facilitated arXiv:1912.06179v1 [physics.optics] 12 Dec 2019 by the thermocapillary (TC) effect; theoretical study of self-induced focusing and defocusing effects of propagating SPPs due to nonlocal interaction [36] (where refractive index changes extend beyond the regions of maximal optical intensity) as well as formation of an optical liquid lattice of a fixed square symmetry, and experimental demonstration of TC-assisted optical tuning of surface plasmon resonance coupling angle [37].…”