An information recording and reproducing apparatus comprising: (a) a recording medium comprising a matrix formed on a substrate and having dispersed in it semiconductor fine particles, (b) a ring resonator formed by a partially transmitting mirror and a first fully reflecting mirror, which are placed on opposite sides of said optical recording medium, a second fully reflecting mirror located so that it receives light from said first fully reflecting mirror and a third fully reflecting mirror located so that it receives light from said second fully reflecting mirror and directs that light to the said partially transmitting mirror, (c) an optical head that transmits and focuses light to said optical recording medium, and (d) one of detecting means that detects an intensity of light for reproduction received from said recording medium and detecting means for detecting a change over time in light for reproduction received from said recording medium.