Nanoplasmonics and metamaterials have been two interplayed and heated topics for over a decade. This issue on nanoplasmonics and metamaterials compiles 10 well-prepared manuscripts, most of which are meticulously performed reviews of the available current literature.

This issue contains two review articles. R. Yang and Z. Lu review the progress of subwavelength or deep subwavelength plasmonic waveguides and fabrication techniques of plasmonic materials, including the theory of plasmonic waveguides, the mode size defined by plasmonic waveguides, spoof plasmonic waveguides, and various media for plasmonic waveguide. D. R. Chowdhury et al. present a review of different coupling schemes in a planar array of terahertz metamaterials. The different coupling mechanisms in planar metamaterials could be exploited for the development of terahertz devices with various functionalities.

Three papers address the theory and applications of metamaterials with abnormal electromagnetic properties. S. Li et al. developed a Green function formulism to calculate the electromagnetic fields generated by sources embedded in nanostructured medium which could be represented by an effective permittivity tensor with finite thicknesses. An extreme case is material with indefinite permittivity tensor, which contains both positive and negative elements. One result is its unique hyperbolic dispersion. A. Kaur et al. studied the electromagnetic properties of wired media and explored their hyperbolic dispersion when used in imaging systems. Based on hyperbolic dispersion, deep subwavelength focusing (or power concentration) is demonstrated both numerically and experimentally. The results verify that hyperbolic metamaterials can focus a broad collimated beam on a subwavelength scale. G. Martínez-Niconoff et al. describe the synthesis of optical singularities propagating in free space and on a metallic surface, where a slit-shaped curve as a boundary condition is applied. They show that singularities in free space may generate bifurcation effects.

Three articles discuss the applications of novel metallic gratings or periodic structures. M. Mirotznik et al. describe a novel infrared sensing technique using plasmonic resonant dust particles. They present computational and experimental results of dust particles that can be tuned to preferentially reflect or emit IR radiation within the LWIR (8–14 μm) band. This technique creates distinct IR absorption resonances by combining the plasmonic resonance of the grating with the natural resonance of the cavity. R. Marani et al. analyze plasmonic bandgaps in a one-dimensional array of slits on metal layers excited by out-of-plane sources. They demonstrate through finite-element simulation that a nonzero angle of incidence induces the formation of an effective finite bandgap. J. Tan et al. analyze the anomalous beam propagation in low-index-contrast metamaterials, which is formed by patterning periodic arrays of air holes in polymer with a low refractive index. The requirements for achieving well-collimated beams in a metamaterial are established.

Two papers deal with the applications of surface plasmons in nanophotonic circuits and nanolithography. Y. Huang et al. present novel plasmonic devices based on metal-dielectric-metal (MDM) stub resonators for manipulating light at the nanoscale. In particular, they demonstrate slow-light effect, a plasmonic analog of electromagnetically induced transparency, and absorption switches based on subwavelength MDM waveguide side coupled to one or more MDM stub resonators. A. Estroff and B. W. Smith explore the applications of surface plasmons based on tuning metamaterials in DUV lithography and propose a method for performing plasmonic interference lithography, with calculations showing the potential for half-pitch imaging resolution of 25 nm.

By compiling these papers, we hope to enrich our readers and researchers with respect to nanoplasmonics and metamaterials.

Zhaolin Lu
Xiaoyue Huang
Mark Mirotznik
Georgios Veronis
Qiwen Zhan