Searcharxiv⌕ Search

arXiv subjects

Amir Djalalian-Assl

Publications and source records attributed to Amir Djalalian-Assl.

12 recordsLinked to original sources
arXiv2021

From Classical Superposition of Waves to Quantum Interference: Three Level Quantum System for Two Entangled Photons

Properties and applications of a plasmonic cross-shaped nano-antenna is presented and compared to those of array of holes. A simple analytical model based on the superposition of waves are proposed and compared to the numerical results. A direct consequence of unequal path for two orthogonal surface waves leads to a coherent quantum interferometer with interesting properties. Mechanism behind the rotating surface charge densities and consequently, the formation of rotating resultant dipole moments is identified and the concept of Dipole-SPP-LSP-Stokes coupling is introduced. All of which leads to the most significant findings (a) foundation of a three-level quantum system for entangled photons, based on the polarization states of the transmitted light and (b) further encapsulation of the three-level quantum system into a continuous orthonormal set of pure quantum states (c) an inference on the nonexistence of spin in a single photon, hence the requirement of two photons to create such spin states.

physics.optics↗
arXiv2020

Design, Fabrication and 3D Volumetric Characterization Criteria for Plasmonic Bullseye Structures

In this report, certain claims regarding the design criteria and characterizations of plasmonic bullseye (BE) structures are investigated. Does the matching of the grating's periodicity to the wavelength of surface waves results in a strong collimated beam along the optical axis of the device? What are the requirements for such devices if they are set to enhance the radiative decay rate of a quantum emitter? These questions are answered by proposing and modelling a new bullseye structure, optimized based on maximization of the far-field intensity along the optical axis. Dimensions and the performance of the proposed BE are then compared to that reported by another author. The other question to be answered is the characterizations techniques. What is the best approach in characterizing such devices? How many focal points are there along the optical axis? What are the strengths and depths of focus at each point? How collimated is the output beam? Techniques proposed by other authors are debated and a technique based on 3D confocal microscopy is proposed and applied experimentally to the alternative proposed device.

physics.optics↗
arXiv2020

Fabrication and Characterization of Resonant Aperture Antenna Arrays

Here I report on comparisons between two different techniques in fabricating arrays of subwavelength cross-shaped apertures in metallic screens. The aim was to determine the most appropriate fabrication technique to be used considering the cost, ease of fabrication and accuracy in which the apertures were created. Some interesting physical effects are observed.

physics.app-ph↗
arXiv2020

Optical Nano-antennas

This report is concerns with optical nano-antennas in their various forms such as metallic nano-rods, cross-shaped nano-particles and apertures, periodic meta-surfaces such hole arrays and bullseye structures. Their applications in wavelength division multiplexing/demultiplexing, shaping the radiation pattern and the state of polarization of the transmitted light, refractive index based sensing, enhancement to the radiative decay rate of nearby quantum emitters and novel approach in achieving such effects are presented.

physics.optics↗
arXiv2019

Surface Plasmon Wave plates

Here I investigate both numerically and experimentally, the polarization conversion capabilities of a rectangular array of holes with two unequal orthogonal periodicities. We show that it is possible to tune the periodicities in such a way that the transmitted light is circularly polarized for a nominated wavelength, Lambda-CPL, when the structure is illuminated with appropriately oriented linearly polarized light at normal incidence. A device was fabricated and experiments confirmed that a degree of circular polarization of 0.89 could be achieved at the resonant wavelength.

physics.optics↗
arXiv2019

Mechanisms governing resonant shifts and resilience in optical responses of plasmonic hole arrays

This report concerns with the theoretical studies of SPP Bloch waves in arrays of cylindrical holes. Most analytical solutions are simplified, approximate and fitted, thus leading to wrong design parameters. A rigorous analytical solution that can accurately predict the desired dimensions associated with hole arrays is complex to derive. Finite element analysis (FEA), on the other hand, offers extensive capabilities for modelling and simulating the response of periodic structures such as that of an infinite array of holes. In this chapter, a square array of cylindrical holes is modelled numerically. A simple analytical model is presented (not for design purposes) only to identify the origin of the alleged (1,1) and (0,2) modes and the results are compared to the numerical ones. Changes in the transmission spectrum vs the refractive index of the surrounding dielectric when illuminated with a linearly polarized light at normal incidence is studied. Circumstances in which an obliquely incident light changes to the SPP momentum are also identified.

physics.optics↗
arXiv2019

Tailoring Properties of Magneto-Optical Photonic Crystals

Magneto-Optic Photonic Crystals (MOPC) used in low dimension lasers whereby acting as Faraday rotators capable of 45o rotation where insertion loos is compensated by photoluminescence effect are of significant interest. In low dimension sensors MOPCs act as optical filters to selectively detect only lights at certain wavelengths. Combined with the photoluminescence effect, sensors may be designed capable of detecting signals with extremely low intensity, thus high quantum efficiency. In this work, MOPC with various Erbium dopant concentrations, acting as photoluminescence center, were modelled under high pumping power regime associated to 0.985 inversion population to identify the minimum Erbium concentration and number of layers for the target 45 degrees FR, 0.9 transmittance and minimal ellipticity at the resonance wavelength 1531nm. Further optimization of Magneto-optical (MO) properties versus the microcavity position within the MOPC was investigated. An optimum multilayered configuration and composition was identified with a reduction in both erbium concentration and total thickness compared to what was reported previously without compromising the target MO properties.

physics.optics↗
arXiv2019

Surface Plasmon-Coupled Enhanced Transmission

For distances less 10 nm, a total energy transfer occurs from a quantum emitter to a nearby metallic surface, producing evanescent surface waves that are plasmonic in nature. When investigating a metallic nanohole supported on an optically dense substrate (such as diamond with nitrogen vacancy center), the scattering occurred preferentially from the diamond substrate towards the air for dipole distances less 10 nm from the aperture. In addition, an enhancement to the dipole's radiative decay rate was observed when resonance of the aperture matched the emitters wavelength. The relationship between an emitter and a nearby resonant aperture is shown to be that of the resonance energy transfer where the emitter acts as a donor and the hole as an acceptor. In conjunction with the preferential scattering behavior, this has led to the proposed device that operates in transmission mode, eliminating the need for epi-illumination techniques and optically denser than air superstrates in the collection cycle, hence making the design simpler and more suitable for miniaturization. A design criterion for the surface grating is also proposed to improve the performance, where the period of the grating differs significantly from the wavelength of the surface plasmon polaritons. Response of the proposed device is further studied with respect to changes in nitrogen vacancy's position and its dipolar orientation to identify the crystallographic planes of diamond over which the performance of the device is maximized.

physics.optics↗
arXiv2019

Ultra-compact Highly Directional Pixel Technology

Attributes such as the Radiative Decay Rate (RDR) and the Radiation Pattern (RP) of Quantum Dots (QDs) are highly sensitive to their nearby surrounding material. To enhance the RDR and shape the RP, interspacing between the QDs and their distances from discontinuities caused by multi-layered environment in which they are immersed, must be controlled with nanoscale accuracy. State of the art in QD based micro-display has so far ignored these aspects of light-matter interaction in pixel design and therefore has been unable to harness the full potential of QDs in pixel size reduction. I propose a novel pixel technology for dynamic micro-displays with novel capabilities such as (1) Each submicron pixel being operable electrically yet independently (i.e. the ability of turning a pixel on/off being independent from the neighboring pixels, hence the infinite contrast ratio. (2) Highly directional light being emitted from each pixel and (3) Increased quantum yield and luminescence while decreasing the number of QDs per pixel, hence minimizing the power consumption

physics.app-ph↗
arXiv2019

Travelling Surface Plasmons with Interference Envelope and A Vision for Time Crystals

The influence of the film thickness and the substrate's refractive index on the surface mode at the superstrate is an important study step that may help clearing some of the misunderstandings surrounding their propagation mechanism. A single sub-wavelength slit perforating a thin metallic film is among the simplest nanostructure capable of launching Surface Plasmon Polaritons on its surrounding surface when excited by an incident field. Here, the impact of the substrate and the film thickness on surface waves is investigated. When the thickness of the film is comparable to its skin depth, SPP waves from the substrate penetrate the film and emerge from the superstrate, creating a superposition of two SPP waves, that leads to a beat interference envelope with well-defined loci which are the function of both the drive frequency and the dielectric constant of the substrate/superstrate. As the film thickness is reduced to the SPP's penetration depth, surface waves from optically denser dielectric/metal interface would dominate, leading to volume plasmons that propagate inside the film at optical frequencies. Interference of periodic volume charge density with the incident field over the film creates charge bundles that are periodic in space and time.

physics.optics↗
arXiv2018

Comments on "Amplifying magneto-optical photonic crystal, Appl. Phys. Lett. 97, 061116 (2010)"

This report concerns analytical solutions predicting the complex refractive indices of doped crystals, based on empirical values of the refractive indices of the dopant and the undoped crystal. An analytical approach in calculating the refractive index of Erbium doped Gadolinium Gallium Garnet was reported by another author previously. My first comment is related to the proposed solution by the other author, where I have shown an alternative approach that leads to a different solution. Although my comments are made in relation to Erbium as the dopant and Gadolinium Gallium Garnet as the undoped lattice, the analytical solution I propose here may be applied to any doped crystals. My second comment concerns the limitations and mistreatment of McCumber relation in this context.

physics.optics↗