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The transmittance, reflectance and absorption of silver nanowires metamaterial embedded into a semiconductor matrix with optical gain are numerically investigated. Metamaterials may suffer from appreciable dissipative losses which are inherent for all plasmonic structures. The losses can significantly be reduced by introducing optical gain in the dielectric matrix by placing atomic or molecular impurities which are pumped by an external light source to create a population inversion. We numerically analyzed the optical properties when the semiconductor host material represents a gain medium. We calculate the transmittance, reflectance and absorption at normal incidence in the visible and near infrared ranges. We observed a peculiar behavior of their optical coefficients that can be explained by observing the field redistribution on the metamaterial.

Split-ring resonator (SRR), one kind of building block of metamaterials, attracts wide attentions due to the resonance excitation of electric and magnetic dipolar response. The fundamental plasmonic properties and potential applications in novel three dimensional vertical split-ring resonators (VSRRs) are designed and investigated. The resonant properties arose from the electric and magnetic interactions between the VSRR and light are theoretically and experimentally studied. Tuning the configuration of VSRR unit cells is able to generate various novel coupling phenomena in VSRRs, such as plasmon hybridization and Fano resonance. The magnetic resonance plays a key role in plasmon coupling in VSRRs. The VSRR-based refractive-index sensor is demonstrated. Due to the unique structural configuration, the enhanced plasmon fields localized in VSRR gaps can be lifted off from the dielectric substrate, allowing for the increase of sensing volume and enhancing the sensitivity. We perform a VSRR based metasurface for light manipulation in optical communication frequency. By changing the prong heights, the 2π phase modulation can be achieved in VSRR for the design of metasurface which can be used for high areal density integration of metal nanostructures and optoelectronic devices. Published version

In the present study, we theoretically investigate how shaping of the light distribution that illuminates a large numerical aperture lens can be used to efficiently couple light to a particular element of optical nano- circuits located at the focal region of the lens. In addition to standard plane waves, we consider illumination schemes that provide peculiar light distributions at focus, such as cylindrical vector beams. These results show that light excitation may be included as an additional degree of freedom in the optimization of optical and metatronic nano- circuitry and their coupling to conventional optical systems.

Holograms, the optical devices to reconstruct pre-designed images, have been evolved dramatically since the advances in today’s nanotechnology [1-4]. Metamaterials, the sub-wavelength artificial structures with tailored refraction index, enable us to design the meta-hologram working in arbitrary frequency region. Here we demonstrated the first reflective type, dual image and high efficient meta-hologram with the incident angle as well as the coherence of incident wave insensitivity in visible region at least from λ = 632.8 nm to λ = 850 nm. The meta-hologram is composed of 50-nm-thick gold cross nano-antenna coupled with 130-nm-thick gold mirror with a 50-nm-thick MgF2 as spacer. It shows different images “RCAS” and “NTU” with high image contract under x- and y-polarized illumination, respectively. Making use of the characteristic of meta-materials, these optical properties of proposed meta-hologram can be transferred to arbitrary electromagnetic region by scale-up the size of the unit cell of meta-hologram, leading to more compact, efficient and promising electromagnetic components. Published version

We present the exciting functionalities of gap surface plasmon-based metasurfaces for light manipulation in reflection due to the excitation of gap surface plasmon resonances allowing for efficient control of phase and amplitude of reflected light. We specifically demonstrate that such plasmonic metasurfaces can be utilized for efficient unidirectional polarization-controlled coupling of incident light to propagating surface plasmon polariton modes. Fabricated metasurfaces that operate at telecommunication wavelengths 1500-1600nm feature a maximum coupling efficiency of ~25% for either of two linear polarizations of incident light and surface plasmon directivity exceeding 100.

We show how transformation optics can enhance optical gradient forces between two optical waveguides by several orders of magnitude. The technique is based on a coordinate transformation that alters the perceived distance between the waveguides. This transformation can be implemented using single-negative metamaterial thin films. The process is remarkably robust to the dissipative loss normally observed in metamaterials. Therefore, our results provide an alternative way to enhance optical forces in nanophotonic actuation systems and may be combined with existing resonator-based enhancement methods to produce optical gradient forces with unprecedented amplitude [Phys. Rev. Lett. 110, 057401 (2013)].

In the last decade, a new area of photonics research has emerged, that has given the ability to produce materials with entirely novel electromagnetic properties. These new materials are known as "metamaterials" for their ability to take beyond conventional materials. Clearly, the field of metamaterials can develop mould-breaking technologies for a plethora of applications, where control over light (or more generally electromagnetic radiation) is a prominent ingredient--among them telecommunications, solar energy harvesting, biological and THz imaging and sensing, optical isolators and polarizers. In this talk, I give an introduction into this emerging field, review recent progress, and highlight remaining challenges and opportunities.

In the last decade, a new area of photonics research has emerged, that has given the ability to produce materials with entirely novel electromagnetic properties. These new materials are known as "metamaterials" for their ability to take beyond conventional materials. Clearly, the field of metamaterials can develop mould-breaking technologies for a plethora of applications, where control over light (or more generally electromagnetic radiation) is a prominent ingredient--among them telecommunications, solar energy harvesting, biological and THz imaging and sensing, optical isolators and polarizers. In this talk, I give an introduction into this emerging field, review recent progress, and highlight remaining challenges and opportunities.

Since a few years, it has been proposed to harness optical forces, i.e., the forces that arise when linear momentum is transferred from photons to matter, in micro- and nanophotonic systems. Most attention was focused on optical forces in waveguides, where resonant waveguide modes enable forces on the space scale of the wavelength of light. Recently, we have extended such research to subwavelength structures. We start this communication with a study of optical forces in a prototype of metamaterial constituents--the nanowire pair. We show how the electric and magnetic dipole resonances lead to repulsive and attractive forces, respectively. However, the stacking of nanowire pairs in an array as in metamaterials may dramatically change the nature of optical forces, e.g., changing the forces associated with the electric dipole resonance from repulsive to attractive. In the second part of this communication, we show how the optical force can be exploited for the creation of nonlinear metamaterials. By optimizing asplit-ring resonator structure for the enhanced interaction between the elastic and the electromagnetic modes mediated by the optical force, we demonstrate metamaterials with a transmission spectrum that depends on the power of the incident electromagnetic wave. This metamaterial thus allows for the switching of its transmittance by simply changing the incident beam power.

Recently, there has been a lot of interest in electromagnetic analogues of general relativistic effects. Using the techniques of transformation optics, the material parameters of table-top devices have been calculated such that they implement several effects that occur in outer space, e.g., the implementation of an artificial event horizon inside an optical fiber, an inhomogeneous refractive index profile to mimic celestial mechanics, or an omnidirectional absorber based on an equivalence with black holes. In this communication, we show how we have extended the framework of transformation optics to a time-dependent metric - the Robertson-Walker metric, a popular model for our universe describing the cosmological redshift. This redshift occurs due to the expansion of the universe, where a photon of frequency omega_em emitted at instance t_em, will be measured at a different frequency omega_obs at time t_obs. The relation between these two frequencies is given by omega_obs a(t_obs) = omega_em a(t_em), where a(t) is the time-dependent scale factor of the expanding universe. Our results show that the transformation-optical analogue of the Robertson-Walker metric is a medium with linear, isotropic, and homogeneous material parameters that evolve as a given function of time. The electromagnetic solutions inside such a medium are frequency shifted according to the cosmological redshift formula. Furthermore, we have demonstrated that a finite slab of such a material allows for the frequency conversion of an optical signal without the creation of unwanted sidebands. Because the medium is linear, the superposition principle remains applicable and arbitrary wavepackets can be converted.