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

A method of optically playing back an optical recording medium having a recording region at least partly composed of a laser medium extending thicknesswise thereof, said recording region having pits and lands formed on a surface thereof as representing recorded information, said pits and lands having respective first surfaces parallel to corresponding second surfaces on an opposite surface of the recording region, said first and second surfaces providing different thicknesses of the recording region, whereby said recording region can operate as optical resonators between said first and second surfaces for emitting laser signal light of a variable frequency depending on said recorded information in response to pumping light applied to the recording region, said optical resonators having respective optical axes extending thicknesswise of said recording region, said method comprising the steps of:

• applying pumping light to said recording region to cause the recording region to operate as optical resonators between said first and second surfaces for emitting laser signal light of a variable frequency depending on said recorded information;
• and
• detecting a change in the frequency of said signal light to reproduce said recorded information.