PURPOSE: To satisfy the conditions of executing reproduction at a high speed and good S/N and to increase the recording density to the maximum by selecting the specific wavelength region in a nonuniform absorption band and boring deep holes.

CONSTITUTION: The nonuniform absorption band of an org. light absorption center is made of superposition of some transitions and the component to constitute a deep and sharp hole among these transitions is known as 0-0 transition which induces an electronic transition without entailing its own vibration excitation and the vibration (phonon) excitation of the matrix surrounding the circumference thereof. It is effective from experiment to adopt the means of recording only in the wavelength region where the component of the 0-0 transition occupies ≥20% of the absorption of the entire part. The backfill of the holes increases significantly and the increase of the recording density is eventually infeasible if an attempt is made to execute recording in the wavelength region wider than the above-mentioned region in order to increase the degree of multiplexion. The recording density is effectively increased by using the widest possible region (1/2) in the wavelength region of ≥20% as the recording and reproducing region.