Estimation of maximum temperature and thermal crosstalk between two active elements in a PIC: development of a thermal equivalent circuit.

The operating temperature plays a key role in the performance and lifetime of photonic integrated circuits (PICs). Miniaturization and increasing heat dissipation promote thermal crosstalk effects and pose additional challenges to the PIC designer. The European Photonics Industry Consortium recommends thermal modeling during design phase. However, a fully numerical optimization of a particular layout requires an unrealistically large number of simulations. Here, we propose a compromise approach: a set of carefully chosen simulations are performed with a multi-physics software. The obtained results are used to derive a linearized equivalent thermal circuit that can be used to maximize the power levels and to minimize the distance between the chosen components while guaranteeing the absence of a thermal crosstalk. For simplification, this model is derived considering a PIC with only two active components. Other parameters are varied, such as the material of the holder (silicon or diamond) and the layer of epoxy that is used to attach the PIC to the holder. The obtained circuit is used to determine the maximum dissipated power or the minimum distance between the components while keeping some predetermined specifications. The model can be extended to contain more elements or to include transient analysis of the temperature distribution.

Ultrahigh Casimir interaction torque in nanowire systems.

We study the Casimir torque arising from the quantum electromagnetic fluctuations due to the interaction of two interfaces in a system formed by a dense array of metallic nanorods embedded in dielectric fluids. It is demonstrated that as a consequence of the ultrahigh density of photonic states in the nanowire array it is possible to channel the quantum fluctuations, and thereby boost the Casimir torque by several orders of magnitude as compared to other known systems (e.g., birefringent parallel plates).

Metamaterials controlled with light.

We suggest and verify experimentally the concept of functional metamaterials whose properties are remotely controlled by illuminating the metamaterial with a pattern of visible light. In such metamaterials arbitrary gradients of the effective material parameters can be achieved simply by adjusting the profile of illumination. We fabricate such light-tunable microwave metamaterials and demonstrate their unique functionalities for reflection, shaping, and focusing of electromagnetic waves.

Ultraconfined interlaced plasmons.

We describe a mesoscopic excitation in strongly coupled grids of metallic nanorods, resulting from the hybridization of weakly bounded plasmons. It is shown both theoretically and experimentally that the characteristic spatial scale of the interlaced plasmons is determined by geometrical features, rather than from the electrical length of the nanorods, and that due to their wide band nature, weak sensitivity to metallic absorption, and subwavelength mode sizes, such plasmons may have exciting applications in waveguiding in the nanoscale.

Envelope Dyadic Green's Function for Uniaxial Metamaterials.

We introduce the concept of the envelope dyadic Green's function (EDGF) and present a formalism to study the propagation of electromagnetic fields with slowly varying amplitude (EMFSVA) in dispersive anisotropic media with two dyadic constitutive parameters: the dielectric permittivity and the magnetic permeability. We find the matrix elements of the EDGFs by applying the formalism for uniaxial anisotropic metamaterials. We present the relations for the velocity of the EMFSVA envelopes which agree with the known definition of the group velocity in dispersive media. We consider examples of propagation of the EMFSVA passing through active and passive media with the Lorentz and the Drude type dispersions, demonstrating beam focusing in hyperbolic media and superluminal propagation in media with inverted population. The results of this paper are applicable to the propagation of modulated electromagnetic fields and slowly varying amplitude fluctuations of such fields through frequency dispersive and dissipative (or active) anisotropic metamaterials. The developed approach can be also used for the analysis of metamaterial-based waveguides, filters, and delay lines.

Optimizing performance of metamaterial wormhole superabsorbers.

Transmission line-based metamaterials are used to realize and model the conjugate-impedance matched superabsorbers. Here, we formulate an analytical-numerical approach for maximizing the effective absorption cross section of the metamaterial wormhole superabsorber, under the goal of minimizing the complexity of the structure. Analytical expressions for the gradient of the absorption cross section as a function of the structural parameters are derived. Numerical results showing enhanced absorption are obtained under three different optimization strategies: a ring-by-ring approach, a gradient-based optimization, and a mixed algorithm. The best results are achieved with the mixed algorithm, with which it is demonstrated that the optimal wormhole superabsorber significantly outperforms a black body-type absorber of a similar size. This study is of a particular interest for applications of the conjugate-impedance-matched superabsorbers as efficient harvesters of electromagnetic radiation.