Refracting objective optical system and optical recording/reproducing device using the same

摘要

A refracting objective optical system used in recording and/or reproducing information by near field light includes an aspherical lens in which an entrance surface is a continuous aspheric surface of convex shape and an exit surface is a flat surface, and a transparent flat plate joined to the flat surface of the relevant lens. The ray entering a first surface of the lens is refracted at the first surface, transmitted through a second surface and the flat plate, and condensed at a microscopic spot near an exit surface of the flat plate. The transparent flat plate includes a microscopic structure for generating a surface excitation plasmon near a light condensing point of the exit surface.