Applications of surface plasmon and phonon polaritons to developing left-handed materials and nano-lithography

摘要

Despite recent successes in making left-handed materials in the microwave frequency range, there has been little progress in achieving same for infrared frequencies. A novel approach to making a material with negative index of refraction using photonic crystals made of dielectric components with a small (of order minus one) negative dielectric permittivity has recently been proposed. Periodic structures with negative-epsilon dielectrics support surface waves which can have a negative group velocity. The nature of these surface waves depends on the dielectric components: they are surface plasmons for plasmonic materials (such as metals) or surface phonon polaritons for polar crystals (such as SiC, ZnSe, GaP) with the reststrahlen band. The advantages of using phononic materials (long phonon lifetime, scientifically important frequency range) will be illustrated. Depending on the photonic lattice (square or hexagonal), the resulting meta-material can be either isotropic, or strongly anisotropic. Another application of the negative-epsilon materials is nano-lithography. As was suggested earlier (Pendry 2000, Shen and Platzman 2002), any material withε = -1 can be used to significantly enhance near-field imaging. It is shown that a thin slab of SiC is capable to focus the 10.55 micron radiation of a CO_2 laser to several hundred nanometers, thus paving the way for a new nano-lithographic technique: Phonon Enhanced Near Field Lithography in Infrared (PENFIL). Analytic calculations of the fields in the focus of such slab are presented, and parametric dependence on the slab width and phonon lifetime explored.