Tuning surface phonon polaritons -

Abstract

The growing need for the development of nanophotonic devices implies new challenges in describing and manipulating optical and thermal properties in sub- diffraction length scales. Low- loss Surface Phonon Polariton (SPhP) modes supported at the surface of polar materials are promising candidates for realizing this task. These surface waves are evanescent electromagnetic waves localized at the surface of dielectric crystals that result from the coupling between photons and phonons. In this PhD work, we provide a thorough explanation of SPhP modes and then introduce various methods for tuning the different properties of such a near- field radiation. The effect of free carrier concentration on the temporal coherence of surface polaritons is investigated, showing a practical method for enhancing the temporal coherence of thermal light- emitting nano- sources. Changing the surface symmetry of a dielectric crystal is shown to be a pragmatic technique for tuning the region of existence of SPhP modes. And finally, it is observed that the shape of the crystal plays a major role in determining the dispersion relation of these surface modes. FTIR reflectivity measurements are performed on all the samples investigated, and the dielectric properties are obtained from the conventional Kramers- Kronig conversion technique corrected on the basis of Fresnel equations for reflectivity.