(US5796892-A)      The method involves delivering concentrated radiation arriving via a first transparent medium having a first refraction index n1, into a second transparent medium having a second refraction index n2, that is smaller than n1, by a transparent delivery waveguide (3) having a third refraction index n3, equal to or greater than n1. The waveguide has a first, cylindrical intake section (4) and a second, tapered hexagonal radiation delivery section (5) which penetrates into a receiver chamber (1). The intake section (4) fits snugly into an aperture (2) of the receiver chamber and is integral with a tubular concentrator (6). The radiation arrives via the transparent medium and is extracted into the receiver chamber holding the second medium having the refraction index n2.    The guided radiation may be any kind of electromagnetic radiation such as light or radio waves. Pref. it may be concentrated light from any artificial source or concentrated solar radiation. The degree of tapering of the radiation delivery section may vary along the axis. The first transparent medium and delivery waveguide may also be made integral with each other.    USE/ADVANTAGE -   In solar energy plant for delivery of concentrated sunlight into solar receiver. Can also be used in radio telescopes or fibre-optic waveguides. Provides effective extraction of radiation.    (US6188820-B1)      The method involves delivering concentrated radiation arriving via a first transparent medium having a first refraction index n1, into a second transparent medium having a second refraction index n2, that is smaller than n1, by a transparent delivery waveguide (3) having a third refraction index n3, equal to or greater than n1. The waveguide has a first, cylindrical intake section (4) and a second, tapered hexagonal radiation delivery section (5) which penetrates into a receiver chamber (1). The intake section (4) fits snugly into an aperture (2) of the receiver chamber and is integral with a tubular concentrator (6). The radiation arrives via the transparent medium and is extracted into the receiver chamber holding the second medium having the refraction index n2.    The guided radiation may be any kind of electromagnetic radiation such as light or radio waves. Pref. it may be concentrated light from any artificial source or concentrated solar radiation. The degree of tapering of the radiation delivery section may vary along the axis. The first transparent medium and delivery waveguide may also be made integral with each other.    USE/ADVANTAGE -   In solar energy plant for delivery of concentrated sunlight into solar receiver. Can also be used in radio telescopes or fibre-optic waveguides. Provides effective extraction of radiation.