Optične simulacije metamaterialov z negativnim lomnim količnikom

BARTOL, JULIJA (author), Krč, Janez (mentor)

Metamateriali so umetni kompozitni materiali, ki jih sestavljajo gradniki, katerih dimenzije so veliko manjše od opazovane valovne dolžine. Materiali z negativnim lomnim količnikom so materiali, v katerih valovni vektor elektromagnetnega valovanja kaže v nasprotno smer širjenja energije. Ta lastnost se pojavi v materialih, ki imajo hkrati negativno dielektričnost in negativno permeabilnost. Čeprav tovrstnega materiala ni moč najti v naravi, ni nobenega fizikalnega zakona, ki takšen pojav prepoveduje. Izkaže se, da se jih da ustvariti s kombinacijo dveh ali več naravnih materialov, ki jih združimo v neko nanostrukturo. V diplomskem delu sem preučila metamateriale z negativnim lomnim količnikom. Simulacije metamaterialov sem izvajala s programskim paketom Comsol. Najprej sem naredila referenčno simulacijo vpada elektromagnetnega valovanja na gladkem spoju galijevega fosfida in zraka pri treh različnih valovnih dolžinah. Pokazala sem, da je geometrijsko določanje lomnega količnika dovolj natančno. Preučila sem mrežni metamaterial (angl. fishnet metamaterial) in opazovala kaj se dogaja z električnim in magnetnim poljem v notranjosti. Naredila sem simulacije pri različnih faznih zamikih in pokazala, da potuje faza v nasprotno smer, kot bi to pričakovali pri navadnih materialih. S pomočjo faznega zamika sem tudi ocenila lomni količnik. Iz mrežnega metamateriala z negativnim lomnim količnikom sem izdelala model prizme in opazovala, kaj se dogaja z lomom elektromagnetnega valovanja. Izmerila sem kote in izračunala lomne količnike pri različnih naklonih robov osnovnega gradnika. Kot zadnjo strukturo sem preučevala še koaksialni enoplastni metamaterial, kjer sem primerjala svoje rezultate z rezultati iz literature in ugotovila, da je pomembno, kako natančno je definiran model materiala, ki ga uporabimo v simulacijah. Geometrijsko sem določila lomni kot in izračunala lomni količnik za različne modele materiala. Izvedla sem simulacije pri različnih razdaljah med valovodi. Tudi ta metamaterial sem simulirala pri različnih faznih zamikih in na ta način pokazala, da je valovni vektor negativen.

• Language: Slovenian
• Keywords: metamateriali, negativni lomni količnik, optične simulacije
• Work type: Undergraduate thesis
• Organization: FE - Faculty of Electrical Engineering
• Year: 2016
• PID: 20.500.12556/RUL-85930
• Publication date in RUL: 29.09.2016

Secondary language

• Language: English
• Title: Optical simulations of metamaterials with negative refractive index

Abstract

Metamaterials are artificial composite materials with building blocks much smaller than the wavelength of interest. Negative index materials are materials that have wave vector antiparallel to propagation of energy. This phenomenon occurs in materials that have negative permittivity and negative permeability. Although materials with such properties do not occur in nature, there is no physical law that prohibits this phenomenon. Therfore such materials can be artificially created within limits of technology. In this thesis I researched matamaterials with negative index of refraction. First, I performed simulation of electromagnetic wave interacting with gallium phosphide and air. I measured three different wavelengths. I've proven that the geometric determination of the refractive index is sufficiently precise. I examined fishnet metamaterail and observed what was happening with electric and magnetic field inside the metamaterial. I carried out simulations for different phase delays and showed that the phase is propagating in the opposite direction as expected in ordinary materials. With the help of phase shift I evaluated refractive index. I made a model of a prism and observed what was happening with the refraction of electromagnetic waves in the positive and negative refractive index. I measured the angles and calculated refracion indices at different inclination of the main building block boundaries. As my final structure I took a closer look at a coaxial single-layer metamaterial. I compared my results with results written in the article. I have concluded that it is very important how accurately material models (which are used in simulations) are defined. I have geometrically determined refraction angle and calculated refractive index. Again I tried out different phase delays with this metamaterial. I've proven that the wave vector is negative. All simulations were carried out in the software package Comsol.

• Keywords: metamaterials, negative refraction quotient, optical simulations