Nanostructured systems with arbitrary electric and magnetic properties: development and application of an extension of the discrete dipole approximation (E-DDA)

• Autores: Rodrigo Alcaraz de la Osa
• Directores de la Tesis: Fernando Moreno Gracia (dir. tes.), José María Saiz Vega (dir. tes.)
• Lectura: En la Universidad de Cantabria ( España ) en 2013
• Idioma: inglés
• Tribunal Calificador de la Tesis: Gaspar Armelles (presid.), Pablo Albella Echave (secret.), Luis Fernández Barquín (voc.)
• Materias:
  • Física
    • Electromagnetismo
    • Óptica
      • Óptica física
• Enlaces
  • Tesis en acceso abierto en:  UCrea  TDX  TESEO 
• Resumen

  • ABSTRACT: The discrete dipole approximation (DDA) has been successfully applied to many light scattering problems. Simply stated, the DDA is an approximation of the continuum target by a finite array of polarizable points. The points acquire dipole moments in response to the local fields. The dipoles of course interact with one another via their electric and magnetic fields, so the DDA is also sometimes referred to as the coupled dipole approximation. As of today, the method has established itself as one of the best solutions to calculate the scattering of radiation by particles of arbitrary shape. Hitherto, however, the main existing implementations include materials with relative magnetic permeability equal to 1 only, which is correct for all materials in the optical frequency range. Nonetheless, materials with unusual optical properties have arisen recently. This includes the possibility of having both electric and magnetic anisotropic properties (bianisotropic materials) in the most general case. The situation where both the real part of the electric permittivity and the magnetic permeability are negative corresponds to what is known as "left-handed materials", or negative index materials (NIM), with unconventional properties such as negative refraction. The treatment of these materials with a method as contrasted as the DDA provides several advantages, apart from possibly being the only method available in many cases. This PhD Thesis has explored nanostructured systems with arbitrary anisotropic optical properties (both electric and magnetic) by means of an Extension of the Discrete Dipole Approximation (E-DDA). During the development of this dissertation, a computational code (E-DDA code) has been implemented, able to produce comparative results with existing DDA codes, obtaining an excellent agreement. After validation, the method was then applied to a wide range of materials and situations, making a special reference to its application to magneto-optical materials (with an antisymmetric electric permittivity tensor) and composite materials. As a summary, the status of the E-DDA code is mature enough to be applied to very different configurations, making it a very useful, flexible and stable computational tool for calculating scattering and absorption of light by irregular particles, including anisotropic materials both electrically and magnetically at the same time in the most general case.