Can the Wigner transform of a two-dimensional rotationally symmetric beam be fully recovered from the Wigner transform of its one-dimensional approximation?

It is shown that the full four-dimensional Wigner transform of a coherent, rotationally symmetric light beam can be completely recovered by measurement, in one step, of the Wigner transform of an equivalent one-dimensional light beam. The method of generating this equivalent light beam from a two-dimensional circular light beam is presented.     

Hemispherical-rod microlens as a variant fractional Fourier transformer

It is shown that a hemispherical-rod microlens can act as a fractional Fourier transform device with a continuously varying degree of fractionality. It is believed to be the first proposed device to perform such a task; its most immediate applications include optical tomography.     

Design considerations for tunnel diode non-linear transmission lines

A tunnel diode non-linear transmission line has been investigated for second and third harmonic generation purposes. Design criteria are given and performance predictions have been obtained simulating the single diode behavior by means of a polynomial expression. An optimization of the non-linear transmission line as a harmonic generator has been obtained as a function of the number of diodes, their separation distances and the bias voltage.     

Terahertz oscillations in semiconducting carbon nanotube resonant-tunneling diodes

The paper presents the simulation and possible physical implementation of a resonant tunneling diode based on a semiconducting single-walled carbon nanotube, which exceeds the performance of similar resonant tunneling devices based on semiconductor heterostructures. In this respect, the oscillation frequency and the output power are predicted to be greater by one order of magnitude, attaining 16 THz and 2.5 μW, respectively. The generated THz signal is directly radiated into free-space through the injection contacts of the resonant tunneling diode, which have the shape of a bowtie antenna.     

The Aharonov-Bohm effect in the momentum space

The Schrödinger formalism of quantum mechanics is used to demonstrate the existence of the Aharonov-Bohm effect in momentum space and set-ups for experimentally demonstrating it are proposed for either free or ballistic electrons.     

n-step optical simulation of the n-qubit state: Applications in optical computing

A method to implement optically 2ⁿ states in n steps, using n optical position bits, is presented. The implementation of the NOT and C-NOT operations, as well as the Fredkin-Toffoli and conditional sign change gates are also discussed.     

Memory effect in carbon quantum DOT–PEG1500N composites

Electrical measurements performed on films of bare carbon quantum dots (CQDs) as well as of CQD functionalized with PEG_1500N deposited on interdigitated electrodes reveal a significant resistance hysteresis. At room temperature, both systems present a stable memory effect after a large number of cycles, fact associated with the removal of shallow trapping states after the thermal treatment of bare and passivated CQDs films. Temperature analysis of transport properties shows that CQDs functionalized with PEG_1500N present a stable hysteresis as the temperature increases, in contrast to the hysteresis of bare CQD films, which disappears at high temperatures. Several transport mechanisms responsible for the electrical behavior of these systems were analyzed and the role of PEG_1500N as a passivation shell was discussed.     

Terahertz continuous wave amplification in semiconductor carbon nanotubes

Considerable gain at terahertz frequencies can be achieved using the Gunn effect in a semiconductor carbon nanotube array biased with a DC electric field. Potential important applications of this device are in the area of far-infrared spectroscopy and imaging.     

Tunable pulse delay in an anisotropic metamaterial slab

We show that large and tunable pulse delays can be obtained at propagation through an anisotropic metamaterial slab. The pulse delay depends not only on frequency but also on the incident/propagation angle and polarization of the electromagnetic field, the last two parameters being much easier to tune than the frequency of the incident field. Although there is a trade-off between large pulse delay values and large tuning ranges, the pulse delay can be modified several times by changing the incidence angle. The results apply to a wide frequency range, from the visible to the THz spectrum.