Optical transmission through a near-field probe with a semiconducting matter in its core

Abstract

The theory of light transmission through the aperture-type near-field optical probe with a semiconducting matter in its core is presented. It is based on the exact description of the transverse-magnetic (TM) and transverse-electric (TE) eigenmodes inside a conical waveguide with perfectly conducting metallic walls and a dissipative core described by a complex frequency-dependent dielectric function. We concentrate on evaluating the energy density distribution of the electromagnetic field inside a probe with a subwavelength aperture including the region near the tip exit, where it is mainly determined by the contribution of evanescent waves. Significant attention is paid to detailed calculations of the near-field transmission coefficient for semiconducting (GaP, GaN, GaAs, and Si) probes of mesoscopic length and to a comparison of the results obtained with those for the dielectric (SiO2, Si3N4, and diamond) probes. Our calculations indicate a strong enhancement in the transmission efficiency of the semiconducting near-field probes with a high refractive index both in the visible and near-infrared spectral ranges as compared to the conventional fiber or solid quartz tips. It is shown that the optical transmittance for the dominant transverse-electric (TE11) mode is significantly greater than that for the lowest-order transverse-magnetic (TM01) mode.