In an article published in the journal Nanomaterials, researchers presented a cost-efficient optimized cylindrical optical antenna with a wide field of view (FOV) and quick response time due to high-efficient nanomaterials.
In recent years, the requirement for high data rates and the rapid development of numerous digital technologies have made wireless communication a crucial component of telecom equipment.
Visible light communication (VLC) is a new area where there is still a lot of room for research. Electromagnetic (EM) waves are used in this technology as a communication medium. Due to its bandwidth constraint caused by an increase in network traffic, Radio Frequency (RF) communication, a kind of wireless communication, has supported the rising need for fast data rates and more capacity.
Optical Wireless Communication (OWC) and Visible Light Communication (VLC)
The development of optical wireless communication (OWC) as a radio frequency communication substitute technology, particularly for indoor communications, provided a remedy for the need for fast data rates. OWC uses electromagnetic (EM) light waves as the data carrier. It is a potential wireless communications technology because of its great energy efficiency, cheap cost, high security, high data rate, and wide bandwidth.
Infrared radiation (IR), ultraviolet (UV), and visible light (VL) are the optical bands employed in OWC technology as the transmission medium. One of the most useful applications of OWC technology is VLC, which uses the electromagnetic spectrum's visible light as a carrier wave to transport data. VLC is a cutting-edge wireless communication system that can provide high data rates for outdoor and indoor applications.
Cylindrical Glass Structure Doped with SiO2 Nanoparticles
This study used a cylindrical glass structure doped with SiO2 nanoparticles due to its important properties, including low cost, adjustable absorption spectra, high stability, and low relaxation times. Additionally, the proposed structure's cylindrical geometry offers several noteworthy advantages over cubic geometries, including excellent coupling with photodetectors, reasonable sensitivity, and a wide field of view (FOV). Hence, it results in low photon losses and high optical efficiency. Furthermore, the glass cladding directs light to the photodetector edges because this construction intends to capture as much light as possible in the nanoparticles.
Finite-Difference Time-Domain (FDTD) Approach and Monte-Carlo Ray Tracing Method
The researchers adjusted the nanoparticle's size to maximize the overlap between the light source's emission spectrum and the nanoparticle's absorption spectrum. As a result, there were fewer losses when the nanoparticle absorbed and reemitted the incoming light data. They achieved the ideal optical antenna structure by combining the finite-difference time-domain (FDTD) approach with the Monte Carlo ray tracing method to simulate the optical antenna structure. This allowed them to acquire the desired SiO2 nanoparticle absorption and emission spectra.
Photons to Electrical Signal Conversion
The suggested construction exposes a glass cylinder containing core-shell silicon dioxide nanoparticles to white LED radiation. A white LED typically consists of a layer of phosphorescence that serves as a down converter material and a broad band-gap material that produces light in the visible blue part of the spectrum. The additional quantum dots (QDs) function as plasmonic nanoparticles and have different optical characteristics from Si QDs.
Due to the nanoparticles' alteration of the incoming photons' mean free path length, the photons they generate can travel to the borders of the cylinder where the photodetectors are situated. Finally, photodetectors turn the photons they have captured into an electrical signal.
Significant Findings of the Study
The FDTD technique was used to analyze the SiO2 QDs' absorption, scattering, and extinction cross-sections. SiO2 nanoparticles were found to have an ideal radius of 79 nm that matches the spectrum of source white LEDs. This size of SiO2 nanoparticle exhibits cross sections for extinction, scattering, and absorption of 5.05 × 10−13 m−2, 4.4 × 10−13 m−2, and 6.65 × 10−14 m−2, respectively. Researchers used the Monte-Carlo ray-tracing method to simulate the suggested optical antenna numerically and reported the optical efficiency for various substrate sizes and dopant concentrations within the substrate.
It was discovered that the suggested structure's optical efficiency ranged from 1 to 29% for dopant concentrations and sizes of different sizes. For use in VLC applications requiring quick reaction times, the antenna substrate was doped with effective SiO2 quantum dots, which have a shorter relaxation time than phosphorescence-based luminescent solar concentrators LSCs. It is a superb light-collecting antenna with a cylinder-shaped surface and a broad field of vision, freeing a VLC system from active light-tracking devices.
In a further study, researchers aim to use various quantum dots to improve antenna performance at various visible band wavelengths. This would enable wavelength division multiplexing to employ VLC with the antenna for several adjacent users.
Darya Fakhri, Farid Alidoust, Ali Rostami and Peyman Mirtaheri (2022) A Monte-Carlo/FDTD Study of High-Efficiency Optical Antennas for LED-Based Visible Light Communication. Nanomaterials. https://www.mdpi.com/2079-4991/12/20/3594