In this paper, a new approach for the development of planar metamaterial structures is developed. For this purpose, split-ring resonators (SRRs) and complementary split-ring resonators (CSRRs) coupled to planar transmission lines are investigated. The electromagnetic behavior of these elements, as well as their coupling to the host transmission line, are studied, and analytical equivalent-circuit models are proposed for the isolated and coupled SRRs/CSRRs. From these models, the stopband/passband characteristics of the analyzed SRR/CSRR loaded transmission lines are derived. It is shown that, in the long wavelength limit, these stopbands/passbands can be interpreted as due to the presence of negative/positive values for the effective /spl epsiv/ and /spl mu/ of the line. The proposed analysis is of interest in the design of compact microwave devices based on the metamaterial concept.

Equivalent-circuit models for split-ring resonators and complementary split-ring resonators coupled to planar transmission lines

Wave propagation and group velocity

We investigated the propagation of femtosecond laser pulses through a metamaterial that has a negative index of refraction for wavelengths around 1.5 micrometers. From the interference fringes of a Michelson interferometer with and without the sample, we directly inferred the phase time delay. From the pulse-envelope shift, we determined the group time delay. In a spectral region, phase and group velocity are negative simultaneously. This means that both the carrier wave and the pulse envelope peak of the output pulse appear at the rear side of the sample before their input pulse counterparts have entered the front side of the sample.

/pdf/simultaneous-negative-phase-and-group-velocity-of-light-in-a-9d6owd3615.pdf

Simultaneous Negative Phase and Group Velocity of Light in a Metamaterial

This Review provides an introduction to the compensation of loss and amplification of surface plasmons in waveguides and resonators. Future challenges, including how to overcome the large losses present in plasmonic systems that offer strong electromagnetic confinement, are also discussed.

Surface plasmon–polariton amplifiers and lasers

Periodic structures with a sub-wavelength pitch have been known since Hertz conducted his first experiments on the polarization of electromagnetic waves. While the use of these structures in waveguide optics was proposed in the 1990s, it has been with the more recent developments of silicon photonics and high-precision lithography techniques that sub-wavelength structures have found widespread application in the field of pho- tonics. This review first provides an introduction to the physics of sub-wavelength structures. An overview of the applications of sub-wavelength structures is then given including: anti-reflective coatings, polarization rotators, high-efficiency fiber-chip cou- plers, spectrometers, high-reflectivity mirrors, athermal waveg- uides, multimode interference couplers, and dispersion engi- neered, ultra-broadband waveguide couplers among others. Particular attention is paid to providing insight into the design strategies for these devices. The concluding remarks provide an outlook on the future development of sub-wavelength structures and their impact in photonics.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/lpor.201400083

Waveguide sub-wavelength structures: a review of principles and applications

We present the design and implementation of a periodically loaded transmission line, which simultaneously exhibits negative refractive index (NRI) and negative group delay (and, hence, negative group velocity). This is achieved by loading the transmission line in series with capacitors and RLC resonators and in shunt with inductors. We discuss the dispersion characteristics of such a medium and identify the frequency bands of NRI and negative group delay. The structures are theoretically studied using S-parameters simulations on truncated loaded transmission lines of different lengths, and the predicted results are compared to the measured scattering parameters of such lines printed on circuit boards using coplanar waveguide technology.

Periodically loaded transmission line with effective negative refractive index and negative group velocity

Hybrid-mode waveguides consisting of a metal surface separated from a high index medium by a low index spacer have attracted much interest recently. Power is concentrated in the low index spacer region for this waveguide. Here we investigate the properties of the hybrid mode in detail and numerically demonstrate the possibility of realizing compact waveguide bends using this wave guiding scheme.

Propagation characteristics of hybrid modes supported by metal-low-high index waveguides and bends.

Plasmonics has attracted a lot of interest in the past few years because of its unique features, especially for its ability to confine light in extremely small volumes. However, application of plasmonics is restricted by the large propagation loss associated with plasmonic waveguides. On the other hand, dielectric waveguides enjoy low loss, although the mode confinement is relatively weaker. Hybrid plasmonic waveguides (HPWGs), which combine these two guiding mechanisms, allow one to utilize the benefits of both technologies. Over the past few years there have been intense research activities around the world on this new guiding scheme. In this work the operating principle of HPWGs, various HPWG structures proposed by different research groups, and their potentail applications are reviewed.

/pdf/a-marriage-of-convenience-hybridization-of-surface-plasmon-2f1rjl672i.pdf

A marriage of convenience: Hybridization of surface plasmon and dielectric waveguide modes

Hybrid plasmonic waveguides consisting of a metal plane separated from a high-index medium by a low-index spacer have recently attracted much interest. Here we show that, by suitably choosing the dimensions and material properties of the hybrid waveguide, a very compact and broadband TE-pass polarizer can be implemented. Finite-difference time-domain simulation indicates that the proposed device can provide large extinction ratio with low insertion loss for the TE mode.

/pdf/compact-and-silicon-on-insulator-compatible-hybrid-plasmonic-2l9208g3xo.pdf

Compact and silicon-on-insulator-compatible hybrid plasmonic TE-pass polarizer.

We investigate a novel waveguide geometry consisting of a high dielectric medium adjacent to a metal plane with a thin low dielectric spacer. The mechanism of operation is explained and simulation results are presented.

Mo Mojahedi

Papers

Periodically loaded transmission line with effective negative refractive index and negative group velocity

Propagation characteristics of hybrid modes supported by metal-low-high index waveguides and bends.

A marriage of convenience: Hybridization of surface plasmon and dielectric waveguide modes

Compact and silicon-on-insulator-compatible hybrid plasmonic TE-pass polarizer.

Super mode propagation in low index medium