A flat major surface of a disc-shaped substrate (e.g., of glass) is coated with a first light reflective layer (e.g., Rhodium) which is coated with a layer of a dielectric material (e.g., silicon dioxide) highly transparent of light of a frequency supplied by a playback laser, which transparent layer is coated with a second light reflective layer (e.g., Rhodium). The light output of a recording laser, which is intensity modulated in accordance with a signal to be recorded, is focused upon the coated surface of the disc as the disc is rotated. With the peak intensity of the focused light sufficient to at least cause melting of the second reflective layer, an information track is formed as a succession of spaced pits in which the first reflective layer is effectively exposed through the layer of dielectric material. For playback, light of a constant intensity is focused on the information track and the adjacent land areas as the disc is rotated. The focused light is of insufficient intensity to effect melting of the remaining portions of the second reflective layer, but is of a frequency at which the thickness of the dielectric layer exposed through the pits introduces a phase change of approximately (2K+1) .pi. radians between reflected portions of the focused light which fall on the pits and reflected portions of the focused light which fall on the undisturbed areas of the disc, where k is zero or any integer. A photodetector, positioned to receive light reflected from the information track as the pits pass through the path of the focused light, develops a signal representative of the recorded information.
An optical memory element contains first and second reflector films, wherein the first reflector film is made of a material of a sufficiently large light reflectance in a relative sense as compared to the second reflector film, and the second reflector film being made of a material of a sufficiently small thermal conductivity in a relative sense as compared to the first reflector film.
A multi-color, high density recording medium including a substrate having at least two patterned interference filters formed thereon is described. Each of the filters transmits a different wavelength range of visible light and each of the filters comprises an unpatterned interference layer of an inorganic material which is substantially absorption-free in the visible wavelength range of the spectrum. At least one of the interference filters formed on the substrate comprises a first, unpatterned reflecting layer positioned on one side of the respective interference layer, and a second, patterned reflecting layer positioned on the other side of the respective interference layer, such that the pattern of only the first reflecting layer forms the pattern of the at least one interference filter.
Magneto-optic media and system optimization including a set of optimized magneto-optic media for use in a magneto-optic recording and readout system employing an incident readout light beam of a given fixed power, P.sub.o. The beam is delivered in a linearly polarized state to the magneto-optic media and the magneto-optic radiation received from the media is detectable by the system. Each member of the set of media comprises a reflective layer having a predetermined thickness, a first transparent layer overlying the reflecting layer and having a predetermined thickness and refractive index and a second light transmissive layer having a predetermined thickness and exhibiting absorptivity at the wavelength of said incident readout light beam and having magneto-optic conversivity and perpendicular anisotropy. Members of the set of optimized magneto-optic media may further included a third transparent layer overlaying the second transmissive layer and having a predetermined thickness and refractive index. The combination of these layers exhibit antireflectivity and the incident light absorbed in the media is captured in the second light transmissive layer and the predetermined layer thicknesses and refractive index are chosen to maximize signal to noise ratio (SNR) according to the relationship ##EQU1## where r.sub.x represents the reflected component of the linearly polarized incident beam r.sub.y represents the reflected magneto-optically induced component in an orthogonal direction, a.sub.i is the i.sup.th element of the set }a.sub.i }0 that represents variable parameters of the chosen readout system, N is the number of elements in the set {a.sub.i } and f is a function which is determined by the chosen readout system.
An optical recording medium comprising a substrate having thereon a subbing layer and a recording layer, wherein said subbing layer comprises two layers comprising a layer having a relatively high thermal conductivity and a layer having a relatively low thermal conductivity.
An optical coating composition comprising a liquid monofunctional photohardenable acrylic ester monomer having dissolved therein an oligomer having a molecular weight of at least 500 and a photoinitiator system.
