Method for recording on and reading out from optical information recording medium

A method for recording information in an optical information recording medium and thereafter reading out the information from the optical information recording medium, which medium comprises:

• a recording layer having a thickness equal to or greater than 2λ/n, where λ is a wavelength of a recording beam and n is a refractive index of the recording layer, and configured to undergo a change in the refractive index by irradiation with the recording beam;
• and an adjacent layer disposed adjacent to the recording layer at a side opposite to an incident side from which the recording beam enters the recording layer, the method comprising the steps of:
• recording a recording spot by irradiating the optical information recording medium with the recording beam, while shifting a focal position by an offset amount d, which satisfies ω0d3ω0, where ω0 is a radius of the recording spot to be recorded in the recording layer, from an interface between the recording layer and the adjacent layer toward the incident side at a time of recording the information, whereby the refractive index of the recording layer changes at a recording position to record the recording spot;
• and
• reading out the information by irradiating the optical information recording medium with a reading beam, while bringing the reading beam into focus on the interface.