Passage of a Bessel beam through a classically forbidden region

The motion of an electromagnetic wave, through a classically-forbidden region, has recently attracted renewed interest because of its implication with regard to the theoretical and experimental problems of superluminality. From an experimental point of view, many papers provide an evidence of superluminality in different physical systems. Theoretically, the problem of a passage through a forbidden gap has been treated by considering plane waves at oblique incidence into a plane parallel layer of a medium with a refractive index smaller than the index of the surrounding medium, and also confined (Gaussian) beams, still at oblique incidence. In the present paper the case of a Bessel beam is examined, at normal incidence into the layer (Secs. II and III), in the scalar approximation (Sec. IV) and by developing also a vectorial treatment (Sec. V). Conclusions are reported in Sic. VI

Classical vgr≠cv_{gr} \neq c solutions of Maxwell equations and the tunneling photon effect

We propose a very simple but general method to construct solutions of Maxwell equations propagating with a group velocity $v_{gr} \neq c$. Applications to wave guides and a possible description of the known experimental evidences on photonic tunneling are discussed.Comment: 11 pages, Latex2e; to be published in Phys. Lett.

Superluminal, subluminal, and negative velocities in free-space electromagnetic propagation

In this Chapter the time-domain analysis of the velocity of the electromagnetic field pulses generated by a spatially compact source in free space is presented. Recent simulations and measurements of anomalous superluminal, subluminal, and negative velocities are discussed. It is shown that such velocities are local and instantaneous in nature and do not violate either causality or special relativity. Although these effects are mainly confined to the near- and intermediate-field zones, some of them seem paradoxical and still lack adequate physical interpretation.Comment: This is an extended account (21 pages, 9 figures) of my previous work: PRL 102, 02040

Delay time in the transfer of modulation between microwave beams

AbstractMeasurements of delay time relative to the signal transferred from a modulated beam F2 to an unmodulated one F1, both of which operate with a microwave carrier at ∼9.3 GHz, are reported and interpreted. The observed behavior is open to two possible interpretations: one is based on a purely stochastic model that consists of zigzag random paths; the other is based on a more conventional electromagnetic approach, although it maintains some of the characteristics of the stochastic model. The anomalous behaviors here studied can have significant applications in photonics and electro‐optics

Spectral Analysis of Quantum Field Fluctuations in a Strongly Coupled Optomechanical System

With a levitodynamics experiment in the strong and coherent quantum optomechanical coupling regime, we demonstrate that the oscillator acts as a broadband quantum spectrum analyzer. The asymmetry between positive and negative frequency branches in the displacement spectrum traces out the spectral features of the quantum fluctuations in the cavity field, which are thus explored over a wide spectral range. Moreover, in our two-dimensional mechanical system the quantum back-action, generated by such vacuum fluctuations, is strongly suppressed in a narrow spectral region due to a destructive interference in the overall susceptibility