A Subwavelength-Laser-Driven Transmitting Optical Nanoantenna for Wireless Communications

Abstract

Nanoantennas are efficient devices exhibiting large confined electric field enhancements. So far, they have been extensively researched mainly in the receiving mode, which means that the illuminating field is essentially a plane wave. In this paper, we consider the problem of designing an efficient and highly directive transmitting Nanoantenna where the system is energized by a non-plane wave field, a subwavelength laser excitation. Including short-wavelength components allowed us to achieve a 200-nm spot radius, which is a quarter of its incident wavelength (800 nm). Near-and far-field antenna quantities are introduced and calculated using an efficient full-wave multiphysics solver. A nano-scale optical antenna is then presented with optimized dimensions and material settings. Various design curves and insights are also discussed in connection with how issues such as how to define efficiency and determine whether the system is radiating properly.

Fundamental Spacetime Representations of Quantum Antenna Systems

“…Remark 4. It should be noted that in all momentum space integrals of the form (29), a rigorous treatment would require that we place a step function of the form Θ(x 0 − x 0 ) before the integral (or integrand) in order to transition from the time-ordered form (27) to the final expression (29). Here, we are effectively focusing on the causal or retarded radiation problem where it is understood that particles observed at x possess a clock time x 0 that is later with respect to the spacetime creation point x , whose internal clock starts ticking at x 0 ; i.e., x 0 > x 0 and Θ(x 0 − x 0 ) = 1.…”

“…Remark 5. The integral representation of the Green's function (29) can also be put in the following (x, t)-form more suitable for future use in antenna theory:…”

“…We believe that quantum antenna theory and technology may be viewed as an attempt to synthesize three already established subfields: 1) classical antennas [26], [27], 2) optical nanoantennas [28], [29], and 3) quantum emitters [28], [30]. As such, a quantum antenna is often confused with one of these three topics.…”

“…This is not what we understand by the term here. A laser source could constitute a part of the q-antenna system, while a larger part, for example an optical antenna, serves as a secondary reflector as in nanoantennas [29]. Also, an atom emitting a photon after undergoing a transition from excited to ground states is not considered an "antenna" in this paper.…”

Analysis and design of secure quantum communication systems utilizing electromagnetic Schrodinger coherent states

“…55 The antenna excited in this way was shown to exhibit a stable radiation pattern, and its efficiency and gain characteristics were found to improve with optimization of the antenna shape. 56 Since intense subwavelength beams are locked up with the resonant plasmonic surface waves excited by the laser field, this structure may provide a practical realization of an externally controlled classic current shielded from photon back-reaction, 56 leading then to the radiation of coherent states. Subsequently, the well-known ability of laser sources to be directly or indirectly modulated by external driving pulse sources 57 allows easy insertion of an information-carrying time-domain excitation signal u(t) by modulating the subwavelength beam directed at the dipole antenna's gap.…”