arXiv subjects

P. Hazdra

Publications and source records attributed to P. Hazdra.

3 recordsLinked to original sources

arXiv2015

An Analytical Evaluation of The Quality Factor Qz for Dominant Spherical Modes

This paper describes an analytical evaluation of the quality factor Qz in a separable system in which the vector potential is known. The proposed method uses a potential definition of active and reactive power, implicitly avoiding infinite entire space integration and extraction of radiation energy. As a result, all the used quantities are finite, and the calculated Qz is always non-negative function of frequency. The theory is presented on the canonical example of the currents flowing on a spherical shell. The Qz for the dominant spherical TM and TE mode and their linear combination are found in closed forms, including both internal and external energies. The proposed analytical method and its results are compared to previously published limits of the quality factor Q.

physics.class-ph↗

arXiv2013

The Measurable Q Factor and Observable Energies of Radiating Structures

New expressions are derived to calculate the Q factor of a radiating device. The resulting relations link Q based on the frequency change of the input impedance at the input port (Qx, Qz) with expressions based solely on the current distribution on an radiating device. The question of which energies of a radiating system are observable is reviewed, and then the proposed Q factor as defined in this paper is physical. The derivation is based on potential theory rather than fields. This approach hence automatically eliminates all divergent integrals associated with electromagnetic energies in infinite space. The new formulas allow us to study the radiation Q factor for antennas without feeding (through e.g. Characteristic Modes) as well as fed by an arbitrary number of ports. The new technique can easily be implemented in any numerical software dealing with current densities. To present the merits of proposed technique, three canonical antennas are studied. Numerical examples show excellent agreement between the measurable Qz derived from input impedance and the new expressions.

physics.class-ph↗

arXiv2007

Optical Characterisation of MOVPE Grown Vertically Correlated InAs/GaAs Quantum Dots

Structures with self-organised InAs quantum dots in a GaAs matrix were grown by the low pressure metal-organic vapour phase epitaxy (LP-MOVPE) technique. Photoluminescence in combination with photomodulated reflectance spectroscopy were used as the main characterisation methods for the growth optimisation. Results show that photoreflectance spectroscopy is an excellent tool for characterisation of QD structures wetting layers (thickness and composition) and for identification of spacers in vertically stacked QDs structures.

cond-mat.mtrl-sci↗