Theoretical investigation of the influence of a diaphragm on the flat surface of a solid immersion lens on beam parameters

The optical property of a solid immersion lens with a flat surface, coated with an opaque thin film with a rectangular hole is investigated on the bas is of a three-dimensional vector mathematical model. The laser beam is focu sed on the center of the hole. It is shown that the side lobe in the energy flux vector distribution in the focal plane of a solid immersion lens with a large numerical aperture (>1.5) significantly decreased the optical effi ciency of the fens. The results of digital simulation show that an opaque t hin film with a hole, equal or larger than the width of the main lobe, sign ificantly increases the transmission coefficient because it closes the inve rse electromagnetic energy flux in the side lobe. The hole has an unimporta nt influence on the energy flux vector distribution in the main light spot when its dimensions are equal or larger than the dimension of the central l obe of the laser beam. The distribution of electrical and magnetic intensit y is also investigated. (C) 2001 society of Photo-Optical Instrumentation E ngineers.