Reversible recording medium based on optical storage of information, method of reversible recording on such a medium

A process for reversible recording on and reading out a recording medium based on optical storage of at least one piece of information within a layer of a support material comprising:

• making base molecules (M) take on a first collective state (EC1) of molecules in a local zone;
• with the molecules having the first collective state (EC1) of molecules in the local zone being able to generate a first second harmonic signal (SH1) that is characteristic of the first collective state (EC1) of molecules when the molecules are excited by electromagnetic reading radiation;
• selectively applying electromagnetic writing radiation focused in a writing zone that forms a micro-volume of said local zone using a two-photon absorption, thereby transforming a portion of the base molecules (M) of said micro-volume having the first collective state (EC1) of molecules into dimerized molecules (M′) thus making the molecules that have the first collective state (EC1) of molecules pass into a second collective state (EC2) of molecules;
• with the molecules having the second collective state (EC2) of molecules being able to generate a second harmonic signal (SH2) that is characteristic of this second collective state (EC2) of molecules when the molecules are excited by the electromagnetic reading radiation;
• applying an electromagnetic reading radiation over said recording medium with a wavelength able to generate a second harmonic signal (SH2) that is characteristic of the second collective state (EC2) of the molecules,
• wherein the base molecules (M) have a molecular structure that is based on a coumarin skeleton according to:
• where:
• k, n and m are positive numbers, and R and R2 are substituents.