Multilayered Waveguide Memory Developed Scattering Model

Optical memory such as compact disks (CD) and digital versatile disks (DVD) are becoming essential as audio and visual storage media as well as external computer data storage media. Many efforts have been made to increase the memory density of the optical disks such as increasing the numerical aperture of the objective lens and decreasing the light wavelength to blue or purple range. However, the present optical disk memory density has almost reached its upper limitation resulted from the diffraction of electromagnetic wave and the nature of two-dimensional storage mode. Consequently, current endeavors to surpass this limitation are made in two main directions. The one way is to use the near field optics techniques such as employing the solid immersion lens and the aperture system. The other way is to extend the data recording from two-dimension (2D) surface to three-dimension (3D) volume.In this paper, we introduce a novel 3D optical storage method-multilayered waveguides storage (MWS). The principles of MWS are: recording the data in the form of the waveguide defective points for information writing, collecting the radiation scattered from the waveguide defects for date reading and restricting the light within the waveguide layer for layer addressing. All of these have been proved to be feasible by the successful experimental results with 10 layers device demonstrated in this paper.In order to fabricate a real storage system, a variety of usable date writing and reading methods are outlined theoretically in this paper. Among them, "Direct Writing Method" and "Scattering Method" is practical particularly. After studying the waveguide principles and the optical scattering theories, we reach an exponential decay rule of waveguide surface scattering light intensity. Taking into account the condition that scattering light intensity of the whole waveguide is uniform, which meets the requirement of some detectors, we deduce a formula about the relation between variable decay coefficient and conductive light passing distance. Furthermore, the corresponding parameters of the decay coefficient are analyzed through applying the transfer matrix theory. All these efforts contribute to the perfection of the waveguide scattering theory.On the basis of the theories above, an experiment about light scattering on waveguide surface is designed, which not only verifies the correctness of the exponential decay rule of scattering light intensity, but also gives the exact decay coefficients of varied waveguide samples respectively. 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. The success of this experiment makes good preparation for the optimization of MWS device performance.In addition, other high density optical storage methods are introduced in this paper. By comparing the advantages of WMS with which of other methods, we can easily and confidently draw the conclusion: MWS will be the prevalent force influencing the main stream of optical storage in the future.