arXiv subjects

Mahmood Hosseini-Farzad

Publications and source records attributed to Mahmood Hosseini-Farzad.

4 recordsLinked to original sources

arXiv2022

Patterns for ghost imaging generated by the Ising model

We offer new illumination patterns for imaging in all-digital ghost imaging (GI) systems. The digital patterns, written as computer generated holograms on spatial light modulators (SLM), are generated by the Ising model, a well-known ferromagnetic model. In general, Ising patterns are affected by the system temperature and magnetic field. For a modest number of measurements in GI, our simulations suggest that low-temperature Ising patterns outperform random patterns. We also experimentally confirm that Ising masks can be used in quantum GI. Moreover, we present a strategy for applying Ising patterns of different temperatures to obtain high-quality images with the number of measurements approximately equal to the number of pixels in the image.

physics.optics↗

arXiv2020

Developing a time-domain method for simulating statistical behaviour of many-emitter systems in the presence of electromagnetic field

In this paper, one of the major shortcomings of the conventional numerical approaches is alleviated by introducing the probabilistic nature of molecular transitions into the framework of classical computational electrodynamics. The main aim is to develop a numerical method, which is capable of capturing the statistical attributes caused by the interactions between a group of spontaneous as well as stimulated emitters and the surrounding electromagnetic field. The electromagnetic field is governed by classical Maxwell's equations, while energy is absorbed from and emitted to the (surrounding) field according to the transitions occurring for the emitters, which are governed by time-dependent probability functions. These probabilities are principally consistent with quantum mechanics. In order to validate the proposed method, it is applied to three different test-cases; directionality of fluorescent emission in a corrugated single-hole gold nano-disk, spatial and temporal coherence of fluorescent emission in a hybrid photonic-plasmonic crystal, and stimulated emission of a core-shell SPASER. The results are shown to be closely comparable to the experimental results reported in the literature.

physics.class-ph↗

arXiv2019

Buried and ridge graphene-based silicon waveguides for broadband polarization-insensitive amplitude and phase modulators

In this paper, four easy-to-fabricate graphene-based Si waveguide modulators are presented to overcome the strong polarization dependency of graphene-based modulators. The modulation features of two newly proposed structures, i.e. two graphene-based buried silicon waveguides in addition to two standard ridge silicon waveguides at the telecommunication wavelength of $λ=1.55 μm$ are studied. The results show that for certain widths of each waveguide (the height is constant), the amplitude and phase modulations clearly become polarization-insensitive. The amplitude modulation depths for both the TE and TM modes are equal for these optimized waveguides with the precision of $10^{-4} dB/{μm}$. Moreover, in some of the proposed modulators, the maximum variations of the real parts of the effective mode indices (EMI) for both the TE and TM modes coincide with each other with an excellent precision ($5\times 10^{-5}$). This precision value is much smaller than the standard criterion value for confirming a polarization-insensitive phase modulation. Furthermore, the performances of all the structures are studied for all optical telecommunication wavelengths. Even without making any changes to the structures designed at $1.55 μm$ at appropriate wavelength intervals, the structures exhibit polarization-insensitive behaviors.

physics.optics↗

arXiv2019

Fluorescence coherence with anodic aluminum oxide hybrid photonic-plasmonic structure

A class of hybrid photonic-plasmonic structures (HPPS) with vertical cylindrical cavities is proposed and its performance in providing a coherent light from spontaneous emission is investigated. It is shown that the proposed easy-to-fabricate and robust anodic aluminum oxide structure dramatically enhances the temporal and spatial coherence compared to the previously examined HPPS. The physical mechanism of achieving the temporal and spatial coherence is explained based on the special optical properties of the proposed HPPS and it is discussed how this structure enables one adjusting hybrid photonic-plasmonic optical modes to obtain coherence for emitters of different frequencies.

physics.optics↗