Optical recording medium and method of optically playing back same including recording medium structure operating as optical resonators emitting applied pumping light at a variable frequency

摘要

An optical recording medium, typically an optical disc, has a recording region of a laser medium extending thicknesswise thereof, and a reference region positioned radially inwardly of the recording region for emitting reference light. The recording region has pits and lands formed on a surface thereof as representing recorded information. The pits and lands having respective first surfaces parallel to corresponding second surfaces on an opposite surface of the recording region. The first and second surfaces provide different thicknesses of the recording region. When pumping light emitted from a semiconductor laser, for example, is applied to the recording region, the recording region operates as optical resonators between the first and second surfaces for emitting laser signal light of a variable frequency depending on the recorded information. The optical resonators have respective optical axes extending thicknesswise of the recording region.