There is disclosed a new system for recording and reproducing information on a dielectric material by selectively forming electret sites by energy from modulated laser beams. The recorded information is read back by specially constructed MOS FET playback head by detecting the presence or absence of electric fields produced by stored charges in the electret sites on the tape. The dielectric materials must have properties which are constant and stable over wide range of temperatures and frequencies and must be able to retain electric charges for long time.
