Enhanced superlens imaging with loss-compensating hyperbolic near-field spatial filter.

Recently a coherent optical process called plasmon-injection (Π) scheme, which employs an auxiliary source, has been introduced as a new technique to compensate losses in metamaterials. Here, a physical implementation of the Π scheme is proposed for enhanced superlens imaging in the presence of absorption losses and noise. The auxiliary source is constructed by a high-intensity illumination (above 1 mW/µm2) of the superlens integrated with a near-field spatial filter. The integrated system enables reconstruction of an object previously unresolvable with the superlens alone. This work elevates the viability of the Π scheme as a strong candidate for loss compensation in near-field imaging systems without requiring nonlinear effects or gain media.

Enhancement of photothermal heat generation by metallodielectric nanoplasmonic clusters.

A four-member homogenous quadrumer composed of silver core-shell nanostructures is tailored to enhance photothermal heat generation efficiency in sub-nanosecond time scale. Calculating the plasmonic and photothermal responses of metallic cluster, we show that it is possible to achieve thermal heat flux generation of 64.7 µW.cm-2 and temperature changes in the range of ΔT = 150 K, using Fano resonant effect. Photothermal heat generation efficiency is even further enhanced by adding carbon nanospheres to the offset gap between particles and obtained thermal heat flux generation of 93.3 µW.cm-2 and temperature increase of ΔT = 172 K. It is also shown that placement of dielectric spheres gives rise to arise collective magnetic dark plasmon modes that improves the quality of the observed Fano resonances. The presented data attests the superior performance of the proposed metallodielectric structures to utilize in practical tumor and cancer therapies and drug delivery applications.

Quantum entanglement distillation with metamaterials.

We propose a scheme for the distillation of partially entangled two-photon Bell and three-photon W states using metamaterials. The distillation of partially entangled Bell states is achieved by using two metamaterials with polarization dependence, one of which is rotated by π/2 around the direction of propagation of the photons. On the other hand, the distillation of three-photon W states is achieved by using one polarization dependent metamaterial and two polarization independent metamaterials. Upon transmission of the photons of the partially entangled states through the metamaterials the entanglement of the states increases and they become distilled. This work opens up new directions in quantum optical state engineering by showing how metamaterials can be used to carry out a quantum information processing task.

Plasmon Injection to Compensate and Control Losses in Negative Index Metamaterials.

Metamaterials have introduced a whole new world of unusual materials with functionalities that cannot be attained in naturally occurring material systems by mimicking and controlling the natural phenomena at subwavelength scales. However, the inherent absorption losses pose a fundamental challenge to the most fascinating applications of metamaterials. Based on a novel plasmon injection (PI or Π) scheme, we propose a coherent optical amplification technique to compensate losses in metamaterials. Although the proof of concept device here operates under normal incidence only, our proposed scheme can be generalized to an arbitrary form of incident waves. The Π scheme is fundamentally different from major optical amplification schemes. It does not require a gain medium, interaction with phonons, or any nonlinear medium. The Π scheme allows for loss-free metamaterials. It is ideally suited for mitigating losses in metamaterials operating in the visible spectrum and is scalable to other optical frequencies. These findings open the possibility of reviving the early dreams of making "magical" metamaterials from scratch.

Optimizing low loss negative index metamaterial for visible spectrum using differential evolution: comment.

In a recent paper, Zhao et al. [Opt. Express 19(12), 11605 (2011)], proposed the use of differential evolution technique to optimize figure of merit of a negative index metamaterial (NIM) for the visible spectrum. In this comment, we argue that certain ambiguities associated with the effective parameter retrieval should be also addressed in the paper for the accurate implementation of the technique for NIMs. Furthermore, the figure of merit reported in the paper is unrealistically large.

Detailed effects of scattering and absorption by haze and aerosols in the atmosphere on the average point spread function of an imaging system.

The Earth's atmosphere has significant effects on the propagation of electromagnetic (EM) radiation and accordingly degrades the performance of electro-optical systems. These effects are attributed to atmospheric turbulence and to absorption and scattering of EM waves by atmospheric molecules and aerosols. In this paper we develop a detailed model of the effects of absorption and scattering on the optical radiation propagating from the object plane to an imaging system based on the classical theory of EM scattering. Scattering has the effect of de-correlating the light leaving the target from the unscattered light reaching the imaging system, and scattering has the effect of broadening the angle at which the scattered light arrives at the receiver compared to the unscattered light. Absorption has the effect of reducing the amount of power available for the image. Both of these effects depend upon the atmospheric species present, their EM properties, and wavelength. We use this detailed model to compute the average point spread function (PSF) of an imaging system that properly accounts for the effects of the diffraction and scattering, and the appropriate optical power level of both the unscattered and the scattered radiation arriving at the pupil of the imaging system. Since the scattered radiation is temporally and spatially de-correlated from the unscattered radiation, we model the effects of the unscattered radiation and the radiation scattered from the various species as additive in the image plane. The key result of this study is the significant effect of atmospheric scattering on the contrast and spatial resolution of images acquired by imaging systems, due to the increased level of the scattered radiation PSF and the reduced level of the direct radiation PSF, upon increasing the atmospheric optical depth.

Intra-connected three-dimensionally isotropic bulk negative index photonic metamaterial.

Isotropic negative index metamaterials (NIMs) are highly desired, particularly for the realization of ultra-high resolution lenses. However, existing isotropic NIMs function only two-dimensionally and cannot be miniaturized beyond microwaves. Direct laser writing processes can be a paradigm shift toward the fabrication of three-dimensionally (3D) isotropic bulk optical metamaterials, but only at the expense of an additional design constraint, namely connectivity. Here, we demonstrate with a proof-of-principle design that the requirement connectivity does not preclude fully isotropic left-handed behavior. This is an important step towards the realization of bulk 3D isotropic NIMs at optical wavelengths.

Tunable room temperature THz sources based on nonlinear mixing in a hybrid optical and THz micro-ring resonator.

We propose and systematically investigate a novel tunable, compact room temperature terahertz (THz) source based on difference frequency generation in a hybrid optical and THz micro-ring resonator. We describe detailed design steps of the source capable of generating THz wave in 0.5-10 THz with a tunability resolution of 0.05 THz by using high second order optical susceptibility (χ((2))) in crystals and polymers. In order to enhance THz generation compared to bulk nonlinear material, we employ a nonlinear optical micro-ring resonator with high-Q resonant modes for infrared input waves. Another ring oscillator with the same outer radius underneath the nonlinear ring with an insulation of SiO2 layer supports the generated THz with resonant modes and out-couples them into a THz waveguide. The phase matching condition is satisfied by engineering both the optical and THz resonators with appropriate effective indices. We analytically estimate THz output power of the device by using practical values of susceptibility in available crystals and polymers. The proposed source can enable tunable, compact THz emitters, on-chip integrated spectrometers, inspire a broader use of THz sources and motivate many important potential THz applications in different fields.

Distillation of photon entanglement using a plasmonic metamaterial.

Plasmonics is a rapidly emerging platform for quantum state engineering with the potential for building ultra-compact and hybrid optoelectronic devices. Recent experiments have shown that despite the presence of decoherence and loss, photon statistics and entanglement can be preserved in single plasmonic systems. This preserving ability should carry over to plasmonic metamaterials, whose properties are the result of many individual plasmonic systems acting collectively, and can be used to engineer optical states of light. Here, we report an experimental demonstration of quantum state filtering, also known as entanglement distillation, using a metamaterial. We show that the metamaterial can be used to distill highly entangled states from less entangled states. As the metamaterial can be integrated with other optical components this work opens up the intriguing possibility of incorporating plasmonic metamaterials in on-chip quantum state engineering tasks.

Exchanging Ohmic losses in metamaterial absorbers with useful optical absorption for photovoltaics.

Using metamaterial absorbers, we have shown that metallic layers in the absorbers do not necessarily constitute undesired resistive heating problem for photovoltaics. Tailoring the geometric skin depth of metals and employing the natural bulk absorbance characteristics of the semiconductors in those absorbers can enable the exchange of undesired resistive losses with the useful optical absorbance in the active semiconductors. Thus, Ohmic loss dominated metamaterial absorbers can be converted into photovoltaic near-perfect absorbers with the advantage of harvesting the full potential of light management offered by the metamaterial absorbers. Based on experimental permittivity data for indium gallium nitride, we have shown that between 75%-95% absorbance can be achieved in the semiconductor layers of the converted metamaterial absorbers. Besides other metamaterial and plasmonic devices, our results may also apply to photodectors and other metal or semiconductor based optical devices where resistive losses and power consumption are important pertaining to the device performance.

Connected bulk negative index photonic metamaterials.

We show the designs of bulk one- and two-dimensionally isotropic photonic negative index metamaterials working around telecom wavelengths. The designed structures are inherently connected, which makes fabrication by direct laser writing and chemical vapor deposition or other techniques possible.