Study Of Toroid Shaped Coated Nano-Particle Antenna

Existing research shows that nano particles and nanoantennas are capable of producing strong enhanced and highly localized fields, and also shown to have considerable applications in diverse fields of science such as the near field optical microscopy,spectroscopy, bio-sensing, optical devices and many more. Thus the useful results prompt us to implement a more systematic and further exploration on nano-antennas of some specific configurations of interest.The focus of this thesis is put on the investigations on coated nanoparticles, and in particular metal coated nano particles. A Study of an electromagnetic behaviour of both active and passive, toroid shaped, coated nano-particles is presented in this thesis. Using an experimentally validated frequency domain simulator(CST Microwave Studio frequency domain solver), results for the plane wave excitation of both active and passive Toroid-Coated Nano-Particles were taken into consideration.In active case both linear and circular polarized plane wave were used as the source of excitation. It was shown that when the core of T-CNP is active i.e. doped with rare earth erbium Er3+ions, dramatically enhances the SCS and ACS values at its resonance frequency but the gain is affected greatly by how the T-CNP antenna is illuminated with the incident plane wave. An EHD excitation of the active TCNP was also considered and studied by varying the location of the EHD. It was demonstrated that these active Toroid-Coated Nano-Particles can be designed to be resonant with their radiated field response that of the fundamental electric dipole mode, by optimizing their geometry and exciting them either by plane wave or Electric Hertzian Dipole fields. The scattering cross section after exciting it with linear polarized plane wave with a certain orientation was increased by 34 dBsm, at resonance point, from the background. The maximum value of total radiated power ratio(Purcell factor) for the corresponding EHD excitation had an increment of 45 dB. These results confirm the potential usefulness of active T-CNPs for nano-sensor applications.