| 摘要 |
PURPOSE:To attain a maximum SN ratio at the detection time, by adjusting the reflection factor of information modulation of recording medium for a polarized incident luminous flux to increase the SN ratio of detection. CONSTITUTION:An amorphous rare earth transition metal layer consisting of GdTbFe or the like or a crystalline magnetic film 15 consisting of MnBi or the like, a high-refractive index dielectric adjusting layer 20 consisting of SiO or the like, a low-refractive index dielectric such as MgF2 or the like, and a high- refractive index dielectric such as ZrO2 or the like are laminated in order on a substrate 19 consisting of glass, resin, or the like to form a recording medium 22. (S/N)not equal to R1/2(1-R)alphacosdelta (thermal noise limit) and (S/N)proportional (1-R)alphacosdelta (shot noise limit) are true among the phase difference delta between a Fresnel reflection coefficient rx of polarization in the polarization direction and a Kerr reflection coefficient ry due to the magnetooptic Kerr effect, the power reflection factor R(=¦rx¦<2>), the quantity alpha dependent upon the refractive index of the dielectric adjusting layer 20 and the film constitution of the magnetic film 19 and following films, and an optimum reflection factor where the Sn ratio is maximum is allowed to exist. |
