Boris Okorn

An idea for optical DB-like metasurface

An idea for practical implementation of an optical metasurface that behaves similarly to a recently proposed DB boundary is proposed. The D part is based on a thin plasmonic slab operating at plasma frequency, while the B part uses a SRR-like structure based on the D-dot wire. The correctness of this idea is demonstrated by full-wave simulations.

Physically sound model of a non-Foster negative capacitor

ABSTRACT In both engineering and physics communities, it is believed that approximation of a realistic non-Foster negative capacitor (within its operating bandwidth) with an ideal dispersionless negative capacitor is acceptable for practical purposes. However, the ideal negative capacitor is not causal and, therefore, not compatible with basic physics. Its use in the design process is misguiding since it often predicts entirely non-physical behaviour. Here, we show that a realistic negative capacitor can always be modelled as a dispersive voltage-controlled source, the internal impedance of which is an ordinary positive capacitor. This equivalent circuit clearly explains the origin of negative conductance that always accompanies negative capacitance, as well as the background physics of previously reported counter-intuitive phenomena in non-Foster metamaterials. Theoretical analysis was verified by simulations and measurements on an experimental low-frequency (100 Hz–25 kHz) negative capacitor demonstrator. Measurement results agreed well with theoretical predictions, showing that the proposed model is indeed physically sound.

Towards verification of D-dot loop concept in optical regime

A very promising concept of an ‘optical wire’ (‘D-dot wire’) that replaces the flow of the conduction current with the flow of the displacement current has been introduced a few years ago (A. Alu and N. Engheta, All optical metamaterial circuit board at the nanoscale Phys. Rev. Lett., vol. 103, no. 14, p. 143902, 2009; B. Edwards and N. Engheta, Experimental Verification of Displacement-Current Conduits in Metamaterials-Inspired Optical Circuitry, Phys. Rev. Lett., vol. 108, no. 19, p. 193902 5p, 2012). Very recently, this concept has been extended to a so-called ‘D-dot loop’ that is actually a capacitive dual of a classical smali inductive loop antenna (elemental magnetic dipole). The ‘D-dot loop’ might find applications in future optical radiation and scattering systems. The basie idea has already been verified by scaled experiments in RF regime (B. Okorn, S. Hrabar, and J. Sancho-Parramon, Verification of concepts of D-dot wire and D-dot loop in RF regime, 2014 IEEE Int. Symp. Antennas Propag., 2014).

Shaping the light distribution of strongly focused systems for efficient excitation of optical nano-circuits

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.