Third Harmonic THz Generation from Graphene in a Parallel-Plate Waveguide

Graphene as a zero-bandgap two-dimensional semiconductor with a linear electron band dispersion near the Dirac points has the potential to exhibit very interesting nonlinear optical properties. In particular, third harmonic generation of terahertz radiation should occur due to the nonlinear relationship between the crystal momentum and the current density. In this work, we investigate the terahertz nonlinear response of graphene inside a parallel-plate waveguide. We optimize the plate separation and Fermi energy of the graphene to maximize third harmonic generation, by maximizing the nonlinear interaction while minimizing the loss and phase mismatch. The results obtained show an increase by more than a factor of 100 in the power efficiency relative to a normal-incidence configuration for a 2 terahertz incident field

Asymmetric planar terahertz metamaterials

We report an experimental observation of three distinct resonances in split ring resonators (SRRs) for both vertical and horizontal electric field polarizations at normal incidence by use of terahertz time domain spectroscopy. Breaking the symmetry in SRRs by gradually displacing the capacitive gap from the center towards the corner of the ring allows for an 85% modulation of the fundamental inductive-capacitive resonance. Increasing asymmetry leads to the evolution of an otherwise inaccessible high quality factor electric quadrupole resonance that can be exploited for bio-sensing applications in the terahertz region.Comment: 8 pages, 5 figure

Terahertz Faraday rotation in a magnetic liquid: High magneto-optical figure of merit and broadband operation in a ferrofluid

We report on the demonstration of a high figure of merit (FOM) Faraday rotation in a liquid in the terahertz (THz) regime. Using a ferrofluid, a high broadband rotation (11 mrad/mm) is experimentally demonstrated in the frequency range of 0.2–0.9 THz at room temperature. Given the low absorption of the liquid, a high magneto-optical figure of merit (5-16 rad.cm/T) is obtained

Terahertz magnetic modulator based on magnetically clustered nanoparticles

Random orientation of liquid-suspended magnetic nanoparticles (Ferrofluids) gives rise to a zero net magnetic orientation. An external magnetic field tends to align these nanoparticles into clusters, leading to a strong linear dichroism on a propagating wave. Using 10 nm-sized Fe3O4, we experimentally realize a polarization-sensitive magnetic modulator operating at terahertz wavelengths. We reached a modulation depth of 66% using a field as low as 35 mT. The proposed concept offers a solution towards fundamental terahertz magnetic modulators

Compact coplanar waveguide bandpass filter based on coupled S-shaped split ring resonators

This letter is focused on the application of coupled single-layer S-shaped split ring resonators (S-SRRs) to the design of highly compact bandpass filters in coplanar waveguide (CPW) technology. S-SRRs have been previously demonstrated as miniaturized resonators, particularly suited for applications in conjunction with coplanar line geometries. However, size reduction of CPW filters based on impedance inverters and S-SRRs is limited by the inverters. Therefore, this letter proposes an alternative geometry of CPW bandpass filters employing S-SRRs in a configuration based on the theory of coupled resonators. A highly compact third-order bandpass filter is designed using this principle, and the proposed approach is validated through experiment, demonstrating competitive filter performance achieved in an extremely small area

Design and Implementation of a Dual-Axis Solar Tracking System STS

Solar energy is converted into electrical energy using photovoltaic panels. The production of electricity from the solar panel is increased by the increase in the collection of solar radiation by the solar panel. To track the sun in vertical and horizontal directions, a dual-axis tracking prototype has been developed to capture the maximum sun rays by tracking the movement of the sun in four different directions. One axis is horizontal, which allows the solar panel to move left and right. The other axis is vertical and allows the panel to turn up and down. The result of this new development provides the solar panels with extensive freedom of movement. This process makes use of the Light Depending Resistor (LDR), which is important for detecting the sun's light by following the source of the light location. Proteus software is being used to design the circuit for the Arduino mega microcontrollers and H-Bridge IC chip. This implemented system can save more energy and probably offer a greater reduction in cost. The project discusses the process of hardware development and the control process of tracking the sun, as well as the circuit design