Non-resonant two-photon absorption recording material, non-resonant polymer two-photon absorption optical information recording medium, and recording/reproducing method

A non-resonant two-photon absorption recording medium consisting essentially of a non-resonant polymer two-photon absorption compound coated as a recording layer upon a substrate,

• wherein:
• the non-resonant polymer two-photon absorption compound is a polymer compound containing, as a copolymer component, a structure represented by the following formula (1):
• and the polymer compound contains the structure
• at a side chain thereof,
• wherein Y represents a substituent having a Hammett sigma para value (σp value) of 0 or more;
• X represents a divalent substituent having a Hammett sigma para value (σp value) of 0 or more;
• X and Y may be the same as or different from each other;
• n represents an integer of 1 to 4;
• R1 represents a hydrogen atom or a substituent;
• R2 represents a divalent substituent;
• R3 represents a substituent;
• when a plurality of R1, R2 or R3 are present, R1, R2 or R3 may be the same as or different from every other R1, R2 or R3;
• l represents an integer of 1 or more;
• and m represents an integer of 0 to 4;
• and further wherein:
• the non-resonant polymer two-photon absorption compound is a material capable of changing the reflected light intensity or refractive index between before and after two-photon recording by deforming before and after two-photon recording to form a convex geometry on an interface with a layer adjacent to a recording layer containing the non-resonant polymer two-photon absorption compound.