Concentration of light energy within a cone with a metal coating

The spatial structure of light waves of the electric type in a cone with perfectly reflecting metal walls is theoretically analysed. The exact formulas and asymptotic expressions are derived which describe the dependences of the energy density of different components of the field inside the cone on the radial coordinate. A special attention is paid to the study of the character of the field decrease near the cone apex depending on the cone angle and the wavelength. The effects of reflection of waves from the truncated cone-free space interface are studied. The obtained results are used for measuring the transmission coefficient of a truncated cone in the optical range for a broad range of parameters, including the diameter of the output aperture of the order of 0.05 – 0.1 of the wavelength. The possibility of obtaining a high transmission coefficient of light in a truncated metallised cone is theoretically substantiated.