Abstract: A transparent radiation delivery waveguide and a guided radiation receiver assembly using the same, which assembly comprises a first transparent medium with a first refractive index n1, a receiver chamber having an aperture and holding a second transparent medium having a second refractive index n2, and the transparent radiation delivery waveguide having a third refractive index n3 substantially equal or greater than n1. The radiation delivery waveguide n3 consists of a transparent vessel holding a transparent liquid medium and has a first radiation intake portion in optical contact with the first transparent medium and held tightly within the aperture of the receiver chamber, and a second, tapered radiation delivery portion of non-circular cross-sectional shape, projecting into the receiver chamber.