Validity of scalar diffraction theory must be checked, because the size of information mark (pit) of optical disk is comparable with or smaller than the laser wavelength.

Classic scalar diffraction theory can't get correct result when the size of information mark (pit) of read only disk is comparable to or smaller than the wavelength of light.

Comparing the results of the two theories, the conclusions can be made as the followings: firstly, the optimal readout signal modulation will occur when the area of an information mark is a little less than half of that of the readout beam spot according to the scalar diffraction theory.

The attenuation constant is in proportion to the density of the scattering dots, and also increased with the laser beam energy that records the information dots.

To read the information in the waveguide multilayer memory,an optoelectronic detector is used to detect the scattering beams emitted from the information dots on the waveguide surface.

These experimental results contribute to optimize the density and size of the information dots,which leads to better scattering distribution of the information dots on the waveguide surface.

Moreover, the experiment results reflect the trends of the decay coefficient when only changing one of its parameters such as depth or density of the information pits.

Diffraction calculation is the basis of designing optical system of optical disk. Validity of scalar diffraction theory must be checked, because the size of information mark (pit) of optical disk is comparable with or smaller than the laser wavelength. The energy calculation error of scalar theory was investigated firstly. The error was as large as 19% for typical pit size. Then the polarization effect of incident wave was analyzed with coupled wave theory. It is found that the diffraction characteristic...

Diffraction calculation is the basis of designing optical system of optical disk. Validity of scalar diffraction theory must be checked, because the size of information mark (pit) of optical disk is comparable with or smaller than the laser wavelength. The energy calculation error of scalar theory was investigated firstly. The error was as large as 19% for typical pit size. Then the polarization effect of incident wave was analyzed with coupled wave theory. It is found that the diffraction characteristic of TE and TM polarization is far from the result of scalar theory, and difference also exist between TE and TM polarization. The difference can be ascribed to the boundary condition of the electromagnetic field, and it will increase with the decrease of the pit width. The error of scalar diffraction theory is very large for DVD, and vector diffraction theory must be employed to get correct result.

Diffraction calculation is the basis of designing optical system of optical disk. Classic scalar diffraction theory can't get correct result when the size of information mark (pit) of read only disk is comparable to or smaller than the wavelength of light. The disk is modeled as a two dimensional grate in this paper, and formulas of diffracted field are derived employing coupled wave theory when the disk is detected by a plane wave. The curve of diffraction intensity versus pit depth is obtained, and the...

Diffraction calculation is the basis of designing optical system of optical disk. Classic scalar diffraction theory can't get correct result when the size of information mark (pit) of read only disk is comparable to or smaller than the wavelength of light. The disk is modeled as a two dimensional grate in this paper, and formulas of diffracted field are derived employing coupled wave theory when the disk is detected by a plane wave. The curve of diffraction intensity versus pit depth is obtained, and the concept of critical depth is put forward. According to the analysis, the critical depth decreases when transverse dimension of the pit reduce, which will result in the decrease of the diffraction intensity variety and limit the storage density of the optical disk finally. The effect of the detecting plane wave's polarization on the diffraction intensity is also investigated in this paper.

A full vector diffraction theory for optical disk system is described. Firstly the focused incident beam is decomposed into a spectrum of plane waves, and the amplitude vector of each plane wave is acquired. Then the amplitude vectors of diffracted plane waves from the disk are calculated rigorously for each incident plane wave, and the spatial frequency spectrum of the total diffracted field is obtained. Finally the energy flux over the objective pupil is calculated and the read out signal of the optical...

A full vector diffraction theory for optical disk system is described. Firstly the focused incident beam is decomposed into a spectrum of plane waves, and the amplitude vector of each plane wave is acquired. Then the amplitude vectors of diffracted plane waves from the disk are calculated rigorously for each incident plane wave, and the spatial frequency spectrum of the total diffracted field is obtained. Finally the energy flux over the objective pupil is calculated and the read out signal of the optical disk system is obtained. In the diffraction calculation, the optical disk is modeled as a crossed metal grating, coordinate transformation method, coupled wave theory and modal method can be adopted according to the different modals of the information marker. The result of vector theory is far from that of the traditional scalar diffraction theory for a typical DVD system, so vector diffraction theory must be adopted.