Long term optical memory includes a storage medium composed from an array of silicon nanoridges positioned onto the fused silica glass. The array has first and second polarization contrast corresponding to different phase of silicon. The first polarization contrast results from amorphous phase of silicon and the second polarization contrast results from crystalline phase of silicon. The first and second polarization states are spatially distributed over plurality of localized data areas of the storage medium.

A recording layer for an optical data recording medium according to one embodiment of the present invention makes it possible to record an information signal by irradiation with laser beam. The recording layer for an optical data recording medium comprises metal oxides including a Mn oxide, a W oxide, and a Sn oxide. The atomic ratio of Mn with respect to the total number of atoms of metal elements constituting the metal oxides is 3-40 atm %.

Long term optical memory includes a storage medium composed from an array of silicon nanoridges positioned onto the fused silica glass. The array has first and second polarization contrast corresponding to different phase of silicon. The first polarization contrast results from amorphous phase of silicon and the second polarization contrast results from crystalline phase of silicon. The first and second polarization states are spatially distributed over plurality of localized data areas of the storage medium.

Long term optical memory includes a storage medium composed from an array of silicon nanoridges positioned onto the fused silica glass. The array has first and second polarization contrast corresponding to different phase of silicon. The first polarization contrast results from amorphous phase of silicon and the second polarization contrast results from crystalline phase of silicon. The first and second polarization states are spatially distributed over plurality of localized data areas of the storage medium.

Long term optical memory includes a storage medium composed from an array of silicon nanoridges positioned onto the fused silica glass. The array has first and second polarization contrast corresponding to different phase of silicon. The first polarization contrast results from amorphous phase of silicon and the second polarization contrast results from crystalline phase of silicon. The first and second polarization states are spatially distributed over plurality of localized data areas of the storage medium.

Long term optical memory includes a storage medium composed from an array of silicon nanoridges positioned onto the fused silica glass. The array has first and second polarization contrast corresponding to different phase of silicon. The first polarization contrast results from amorphous phase of silicon and the second polarization contrast results from crystalline phase of silicon. The first and second polarization states are spatially distributed over plurality of localized data areas of the storage medium.

An optical memory includes a support and nanoparticles, each of which changes between a crystal phase and an amorphous phase when irradiated with light. The nanoparticles are supported by the support and spaced apart from each other in one or both of an in-plane direction of a face of the support and a direction normal to the face of the support.

An optical memory includes a support and nanoparticles, each of which changes between a crystal phase and an amorphous phase when irradiated with light. The nanoparticles are supported by the support and spaced apart from each other in one or both of an in-plane direction of a face of the support and a direction normal to the face of the support.

A nonlinear light absorption material includes a compound having a nonlinear light absorption property at a wavelength of 390 nm or more and 420 nm or less and represented by the formula (1) as a main component:

##STR00001##

in the formula (1), X is an oxygen atom.

A nonlinear light absorption material includes a compound represented by the following formula (1) as a main component:

##STR00001##

in the formula (1), R.sup.1 to R.sup.6 are each independently a hydrocarbon group.