Beams Phase Research Articles

Analysis of Optical Properties of SiO<sub>2</sub> Thin Films for Various Thicknesses and Substrate Material Using Matlab Code

Theoretical study using mathematical analysis supported by Matlab code was created, for Silicon dioxide (SiO₂) thin films on various substrate materials (Aluminium, quartz, and silicon), and different thicknesses. Reflectance and transmittance of the (SiO₂) thin film is strongly dependent on the electromagnetic wavelength. Many physical results were obtained. The results obtained serve as an illustration of the feasibility of simple techniques in measuring precisely the reflectance and absorptance of the (SiO₂) thin film with an error not exceeding 0.1%. The reflectance and absorptance characteristics of multilayer thin film are strongly dependent on the wavelength of the electromagnetic waves. The effects of various substrate materials on the reflectance characteristics have been investigated by evaluating the reflectance curves of SiO₂ thin films with thickness in the range of (100-1000) nm. The amplitude and periodicity of reflectance and absorptance changed with wavelength. Also the periodicity of this variety change with the film thickness and with the substrate material. In multilayer thin-film devices, the amount of light reflected at each interface can be adjusted by adjusting many factors like film thickness and substrate materials. beams phase can be adjusted by changing the layer thickness. There are thus two parameters associated with each layer, thickness and refractive index difference between film and substrate materials, which can be chosen to give the required performance.

Optical Time Reversal from Time-Dependent Epsilon-Near-Zero Media.

Materials with a spatially uniform but temporally varying optical response have applications ranging from magnetic field-free optical isolators to fundamental studies of quantum field theories. However, these effects typically become relevant only for time variations oscillating at optical frequencies, thus presenting a significant hurdle that severely limits the realization of such conditions. Here we present a thin-film material with a permittivity that pulsates (uniformly in space) at optical frequencies and realizes a time-reversing medium of the form originally proposed by Pendry [Science 322, 71 (2008)SCIEAS0036-807510.1126/science.1162087]. We use an optically pumped, 500nm thick film of epsilon-near-zero (ENZ) material based on Al-doped zinc oxide. An incident probe beam is both negatively refracted and time reversed through a reflected phase-conjugated beam. As a result of the high nonlinearity and the refractive index that is close to zero, the ENZ film leads to time reversed beams (simultaneous negative refraction and phase conjugation) with near-unit efficiency and greater-than-unit internal conversion efficiency. The ENZ platform therefore presents the time-reversal features required, e.g., for efficient subwavelength imaging, all-optical isolators and fundamental quantum field theory studies.

Phase-Sensitive Single-Pixel THz Imaging Using Intensity-Only Measurements

We present a submillimeter-wave phase-sensitive imaging system by using single-pixel, intensity-only measurements. We implement this unique modality by utilizing the photoelectric effect on a high-resistivity silicon wafer illuminated by visible light from a commercial liquid crystal display projector. Randomly distributed mask patterns ( $16\times 16$ pixel) are generated using two levels of light intensity projected on a high-resistivity silicon wafer. The spatial modulation of the amplitude and phase of the incident terahertz is achieved via the photoelectric effect, resulting in the random modulation of the object beams phase fronts accordingly. Subsequently, intensity-only measurements are collected by using a single-pixel sensor for each of the random mask patterns, and the “Phaselift” algorithm is applied to reconstruct the magnitude and phase of the $16\times 16$ pixel image. We also demonstrate that the phase image of the scene shows superior contrast to the intensity image and offers thickness discernibility of a paper object down to 190 $\mu$ m at 690 GHz.

TAB-MAC: Assisted beamforming MAC protocol for Terahertz communication networks

Terahertz (THz) communication is envisioned as one of the key technologies to satisfy the increasing demand for higher-speed wireless communication networks. The very high path loss at THz frequencies and the power limitations of THz transceivers limit the communication distance in THz networks. Beamforming directional antennas are needed simultaneously in transmission and in reception to communicate over distances beyond a few meters. This results in many challenges at the link layer, which cannot be easily addressed with existing Medium Access Control (MAC) protocols. In this paper, an Assisted Beamforming MAC protocol for THz communication networks (TAB-MAC) is presented. The protocol exploits two different wireless technologies, namely, WiFi at 2.4 GHz and THz-band communication. In particular, nodes rely on the omnidirectional 2.4 GHz channel to exchange control information and coordinate their data transmissions (Phase 1), whereas the actual data transfer occurs at THz frequencies only after the nodes have aligned their beams (Phase 2). A mathematical framework is developed to analyze the performance of the TAB-MAC protocol in terms of packet delay and throughput, and theoretical upper bounds are derived as functions of total data size, data frame size, node density and data rate in THz band. Numerical results are provided to evaluate the performance of the proposed protocol under different scenarios and define the protocol design guidelines. The results show that the proposed protocol maximizes the THz channel utilization and achievable throughput.

The Global Symmetry Group of Quantum Spectral Beams and Geometric Phase Factors

We propose a cohomological modelling schema of quantum state spaces and their connectivity structures in relation to the formulation of global geometric phase phenomena. In the course of this schema, we introduce the notion of Hermitian differential line sheaves or unitary rays and classify their gauge equivalence classes in terms of a global differential invariant given by the de Rham cohomology class of the curvature. Furthermore, we formulate and interpret physically the curvature recognition integrality theorem for unitary rays. Using this recognition theorem, we define the notion of a quantum spectral beam and show that it has an affine space structure with structure group given by the characters of the fundamental group.

Research on the diffraction characteristics of phase modulated laser beams dispersed spectrally

It is simulated numerically the transmission of beams phase modulated and spectrally dispersed by the unit for smoothing by spectral dispersion put in the laser driver for inertial confinement fusion. The results show that the diffraction spot of a spectrally dispersed beam becomes larger and its near-field uniformity is improved, while there exists area where the intensity is nearly even within the far-field spot. The effects of the main parameters of the electro-optic phase modulator and the grating in the unit on the diffraction characteristics of the beams are further discussed, and it is found that intensity modulation emerges in the far-field spot under some conditions.

Laser‐Surface Nanostructures in Carbon Coating

In this paper we propose a theoretical basis of a new method of Laser Ablation Lithography (LAL) using coherent laser beams interference patterns. The advantage of our method is the absence of the need to use a mask. In our method the profile of nanostructures surface in carbon coating is produced by an interference laser beam pattern and depends on the following parameters: angle of beams convergence, phase difference, and intensity of the beams, and so forth.

Spatial resolution for two-beam spectroscopy: a new mechanism

With the help of interference effects, two-beam and multiple-beam spectroscopy detect in the pairs of beams (bundles of rays selected by the optical system) phase correlations due to certain fluctuations in optically thin distributions of incoherent light sources. Originally spatial resolution along the line of sight was expected for multiple-beam spectroscopy because of the limited region of intersection for pairs of beams. Here more general analysis shows another mechanism of spatial resolution allowing use of broader overlapping beams. Thus a simpler two-beam spectroscopy configuration (to be discussed in more detail elsewhere) capable of making more efficient use of emitted light proves to offer the same localized measurement of spatially harmonic fluctuations in the appropriate light source distributions.

Investigation of phase density redistribution processes in intense proton beams, extracted from ion sources of duoplasmatron type

The results of measurements of phase density distribution in intensive proton beams, extracted from an ion source of duoplasmatron type, are given and analyzed. It is found that the distribution f in real beams differs considerably from the microcanonical one. By numerical solution of the equation system describing beams with an arbitrary distribution f, it is shown that in investigated beams phase density redistribution takes place, and because of this considerable distortion of current density and phase volume configuration occurs.

Improvements in Optical Fourier Synthesis

A METHOD has recently been described of producing Fourier syntheses of centro-symmetrical projections by means of optical interference1. The biaxial nature of mica was used to introduce into the diffracting beams both intensity and phase relations corresponding to those of the X-ray spectra. The resolution obtained was poor, and it was suggested that this could be improved by using lenses corrected for spherical aberration.