Reflectors and immersion lenses for detectors of diffuse radiation

Abstract

The possibility of using reflectors or immersion lenses to enhance the output of detectors of diffuse (homogeneous and isotropic) radiation encountered in scatter communication systems is examined. Reflectors can yield no optical gain, whereas immersion lenses can provide gain equal to n2, where n is the index of refraction of the immersion medium. The conditions necessary to approach this theoretical maximum are examined from the point of view of geometrical optics. The general conclusions are verified by computer simulations for the spherical geometry. Experiments have been performed with spherical and hemispherical immersion lenses, thus confirming the theoretical predictions.