Hyperbolic Transition Research Articles

Near-Unity Light-Matter Interaction in Mid-Infrared van der Waals Metasurfaces.

Accessing mid-infrared radiation is of great importance for a range of applications, including thermal imaging, sensing, and radiative cooling. Here, we study light interaction with hexagonal boron nitride (hBN) nanocavities and reveal strong and tunable resonances across its hyperbolic transition. In addition to conventional phonon-polariton excitations, we demonstrate that the high refractive index of hexagonal boron nitride outside the Reststrahlen band allows enhanced light-matter interactions in deep subwavelength (<λ/15) nanostructures across a broad 7-8 μm range. Emergence and interplay of Fabry-Perot and Mie-like resonances are examined experimentally and theoretically. Near-unity absorption and high quality (Q ≥ 80) resonance interaction in the vicinity of the hBN transverse optical phonon is further observed. Our study provides avenues to design highly efficient and ultracompact structures for controlling mid-infrared radiation and accessing strong light-matter interactions with hBN.

Infrared metamaterial by RF magnetron sputtered ZnO/Al:ZnO multilayers

Hyperbolic metamaterials create artificial anisotropy using metallic wires suspended in dielectric media or alternating layers of a metal and dielectric (Type I or Type II). In this study we fabricated ZnO/Al:ZnO (AZO) multilayers by the RF magnetron sputtering deposition technique. Our fabricated multilayers satisfy the requirements for a type II hyperbolic metamaterial. The optical response of individual AZO and ZnO films, as well as the multilayered film were investigated via UV-vis-IR transmittance and spectroscopic ellipsometry. The optical response of the multilayered system is calculated using the nonlocal-corrected Effective Medium Approximation (EMA). The spectroscopic ellipsometry data of the multilayered system was modeled using a uniaxial material model and EMA model. Both theoretical and experimental studies validate the fabricated multilayers undergo a hyperbolic transition at a wavelength of 2.2 μm. To our knowledge this is the first AZO/ZnO type II hyperbolic metamaterial system fabricated by magnetron sputtering deposition method.

Analysis of Hyperbolic Transition Curve Geometry

After the description of the basic geometry and relationships of the hyperbolic transition curve geometry we made further analysis. In this paper we analyzed the possible minimal length of the transition curve based on the dynamical characteristics. We determined the relationship between the dynamical parameters and the p parameter of the transition curve. For transition curves between tangential sections and curves we compared the minimal lengths of the hyperbolic geometry to the clothoide and cosine ones. The results show that according to the considered regulations the hyperbolic geometry gives shorter transition curve length. This has significant practical consequences as it makes the design more flexible.

Hyperbolic transition curve

This paper describes a transistion curve geometry based on sine hyperbolic function. This geometry combines the advantages of the widely used chlotoide and cosine transition curves. The hyperbolic transition curve is parameterized, the characteristics of the transition curve depends on the parameter, creating a continuous transition between the chlotoide and the cosine geometry.

Gold-silicon metamaterial with hyperbolic transition in near infrared

In this paper, we focus on the creation and characterization of a hyperbolic metamaterial for near infrared. To shift the hyperbolic transition there, a stack of alternating 7 nm gold and 42 nm silicon layers is chosen. Samples are manufactured using magnetron sputtering and different measurements confirm their structure. We fit the Drude model of gold to reproduce measured reflectivity and transmittance by simulations. The collision frequency of the thin film gold is increased by 9 times, which shifts the transition of our metamaterial to the hyperbolic regime to even larger wavelengths. The performance is comparable to other proposed metamaterials.

標準写像における3周期加速モードの分岐現象

Upon the change of the stochastic parameter, the period-3 accelerator mode of the standard map becomes unstable through hypebolic transition with reflection when the residue R goes over the unity, while it undergoes hyperbolic transition with reflection for the residues R becomes negative. The former case is nothing but the period-doubling bifurcation, in which the formation of new periodic orbits are confirmed with the known symmetry analysis. The hyperbolic transition without reflection however, leads to the birth of a pair of period-3 orbits, which can not he identified as the intersection of known symmetry lines. This finding calls for special interests to explore some kind of hidden symmetry for the hyperbolic transition without reflection in the period-3 accelerator modes of the standard map.

Sedimentation of particles in polymer solutions

In this paper, we present detailed and systematic experimental results on the sedimentation of solid particles in aqueous solutions of polyox and polyacrylamide, and in solutions of polyox in glycerin and water. The tilt angles of long cylinders and flat plates falling in these viscoelastic liquids were measured. The effects of particle length, particle weight, particle shape, liquid properties and liquid temperature were determined. In some experiments, the cylinders fall under gravity in a bed with closely spaced walls. No matter how or where a cylinder is released the axis of the cylinder centres itself between the close walls and falls steadily at a fixed angle of tilt with the horizontal. A discussion of tilt angle may be framed in terms of competition between viscous effects, viscoelastic effects and inertia. When inertia is small, viscoelasticity dominates and the particles settle with their broadside parallel or nearly parallel to the direction of fall. Normal stresses acting at the corners of rectangular plates and squared-off cylinders with flat ends cause shape tilting from the vertical. Cylinders with round ends and cone ends tilt much less in the regime of slow flow. Shape tilting is smaller and is caused by a different mechanism to tilting due to inertia. When inertia is large the particles settle with their broadside perpendicular to the direction of fall. The tilt angle varies continuously from 90° when viscoelasticity dominates to 0° when inertia dominates. The balance between inertia and viscoelasticity was controlled by systematic variation of the weight of the particles and the composition and temperature of the solution. Particles will turn broadside-on when the inertia forces are larger than viscous and viscoelastic forces. This orientation occurred when the Reynolds number Re was greater than some number not much greater than one in any case, and less than 0.1 in Newtonian liquids and very dilute solutions. In principle, a long particle will eventually turn its broadside perpendicular to the stream in a Newtonian liquid for any Re &gt; 0, but in a viscoelastic liquid this turning cannot occur unless Re &gt; 1. Another condition for inertial tilting is that the elastic length λU should be longer than the viscous length ν/U where U is the terminal velocity, ν is the kinematic viscosity and λ = ν/c2 is a relaxation time where c is the shear wave speed measured with the shear wave speed meter (Joseph 1990). The condition M = U/c &gt; 1 is provisionally interpreted as a hyperbolic transition of solutions of the vorticity equation analogous to transonic flow. Strong departure of the tilt angle from θ = 90° begins at about M = 1 and ends with θ = 0° when 1 &lt; M &lt; 4.

Independent confirmation that delayed die swell is a hyperbolic transition

We measured shear wave speeds in the same aqueous Xathan solutions used to study delayed die swell by Allain et al. (Eur. J. Mech. A/Fluids, 12 (1993) 175-186). They reported delayed die swell for solutions of 500, 1000, 2000 and 4000 ppm Xanthan in water when the shear rate, 8 U/d, was above a critical value 8 U c/ d, where U is the mean velocity through a round pipe of diameter d = 0.6 mm and U c is a critical value. Their photographs of delayed die swell are exactly like those reported by Joseph et al. (J. Non-Newtonian Fluid Mech., 24 (1987) 31-65) for 17 different polymer solutions, by Joseph (Fluid Dynamics of Viscoelastic Liquids, Springer-Verlag, New York, 1990) for 18 and by Hu et al. (J. Non-Newtonian Fluid Mech., 35 (1990) 287-307) for Ml. Allain et al. sent us samples of the four solutions, prepared by them, and we measured wave speeds on our meter. As in all the earlier experiments, the delay occurs when the centerline velocity in the pipe U = 2 U is greater than the wave speed C, and after a distance L the swell is complete and the mean velocity is less than C. This adds four more cases, 23 in all, to those for which the delay can be correlated with the wave speed measured on our meter. So far 23, and only 23, cases have been studied and they are all consistent with calculations from theory giving rise to hyperbolicity and change of type.

Reflection of VLF radio waves from an inhomogeneous ionosphere. Part III. Exponential model with hyperbolic transition

This is a continuation of two earlier papers on the subject of reflection of waves from inhomogeneous isotropic media. In this particular paper an exponential conductivity profile is perturbed in such a manner that the conductivity is increased for all heights above a certain level. A hyperbolic tangent transition is employed in order to avoid discontinuities in the conductivity versus height profile.