43924-G10
Plasmonics of Composite Materials: New Avenues of Light Management on the Nanoscale
The PRF proposal contained four major tasks:
[1]. Reflection/refraction and scattering of surface waves in isotropic systems
[2]. Surface waves and material anisotropy
[3]. Nonlinear response of surface modes
[4]. Localization of surface modes and applicability of effective-medium descriptions
As of today, the active research on the project is almost complete. Most of our results have been summarized in recent publications; several more publications are being finalized for submission. Below we describe our major PRF-funded achievements in more details.
A. Previous achievements
As detailed in our first progress report, we have
1. Developed analytical description of (nonlocal) response of plasmonic composites; this set of projects partially completed tasks [2] and [4] of the original proposal.
2. Developed a description of the effect of material gain on the propagation of surface modes in active metamaterial systems and (in collaboration with group of Prof. Noginov, NSU) verified our theoretical predictions. This project partially completed task [3] of the proposal
3. Analyzed the behavior of planar lens based on anisotropic metamaterials as partial completion of task [1]
Thus, as of 08/31/07 tasks [2], [3] and [4] were partially completed.
B. Current results
I. Resolution of the superlens
Our second project this year was focused on the 10-year-long controversy regarding the resolution of the planar lens based on the negative refractive index material, known as superlens. On one hand, mode-matching simulations have predicted subwavelength resolution of this structure. On the other hand, the diffraction theory predicted that the far-field resolution of the planar lens is always limited by the wavelength.
We have demonstrated that conventional criterion of applicability of diffraction theory cannot be used to describe the behavior of the superlens. We have also developed a correct criterion that incorporates material loss (as the main resolution-limiting factor) in addition to the wavelength and size of the structure. Finally, we have derived the expression of the far-field resolution of the superlens, and provided a link between the excitation of surface plasmon polaritons and the onset of sub-wavelength resolution. The results of this study are summarized in a manuscript published in Phys.Rev.B.
In a separate project, we have calculated the resolution of the superlens based on anisotropic multilayer metamaterials; these results are summarized in a publication in Phys.Rev.Lett.
II. Active plasmonics
Our main focus this year was on completion of the set of projects related to elimination of losses in plasmonic structures with material gain in the adjacent dielectric layer. This work is a continuation of our collaboration with Prof. Noginov’s group at NSU. We have been able to achieve stimulated emission of surface plasmon polaritons, signified by nonlinear response of input-output curves and simultaneous reduction of the emission linewidth. This result represents the first observation of complete compensation of loss of propagating surface waves. In particular, our work opens the road to further increase the resolution of the superlens. The manuscript detailing this work is currently under consideration in Phys.Rev.Lett
In a separate project, we are currently working on understanding of lasing-like behavior of plasmonic nanoparticles covered with dye medium, previously observed by the NSU team. The results of this project will be summarized in our upcoming publication.
Finally, we have proposed a criterion for selection of the sign of refractive index in active metamaterials.
These two projects will complete tasks [3] and [4] of the original proposal.
III. Scattering by anisotropic resonators
This project is a continuation of our work on anisotropic negative-index materials. We have developed a set of numerical techniques capable of analyzing the scattering by microresonators comprised from anisotropic media. Our first results indicate that the response of anisotropic systems is very different from the response of their isotropic counterparts. We anticipate the completion of this ongoing project [co-sponsored by the NSF] over the next year.
Projects II-III partially complete task [2] of the proposal
IV. Planar optics
Finally, we have developed numerical codes to analyze the scattering of SPPs in isotropic media, and used these codes to derive the analytical description of reflection, refraction and scattering of SPPs in isotropic media in the low-scattering regime. We are currently working on extending our results to incorporate material anisotropy.
The "anisotropic" part of this work is a continuation of our recent discovery of no-scattering plasmonic optics, sponsored by the ONR and NSF. We are currently finalizing the manuscript detailing our theoretical results; we plan submitting this work to Phys.Rev.B.
The completion of this project will complete tasks [1] and [2] of the original proposal
The results of all the projects have direct implication for design and development of future high-resolution imaging, sensing, and chemical detection systems.
c. Future work Next year, we plan to complete the ongoing work on understanding the appearance of lasing in nanoparticle metamaterials, on scattering by anisotropic microresonators, and on scattering by plasmonic systems.
