Research On Superresolution Theory Regarding Gaussian Beam And Its Application In High Density Optical Data Storage

With the quick increase of information storage and transmission in our modern society, the relative technologies with high density and large capability became more and more attractive. Especially, the optical data storage technology has experienced a rapid evolution because of its prominent merits. The key of enhancing the capability of the optical disk is to improve the resolution, which lead researchers spend much more time to look for considerate methods. Superresolution, namely improving the resolving power of optical systems beyond the diffraction limit, has attracted considerate attention over the years because of its strong potential in many applications, such as optical data storage, confocal microscopy, astronomy and so on. In this thesis, we focus on studying the superresolution theory regarding Gaussian beam and its application in high-density optical data storage. The researches we have done are as follows:first of all, the superresolution filter has been designed in term of Gaussian beam; then, the superresolution theory regarding Gaussian beam is given and the relative superresolution performances are compared with those for the uniform amplitude incident beam; third, the superresolution filter is applied into the optical pick-up and mastering system; finally, the experiment researches on equipping, adjusting and evaluating the optical pick-up are carried out.Work and innovation of this dissertation include:1. From a practical perspective, we have designed superresolution filters based on a Gaussian beam that allow us to achieve improved resolution properties in optical data storage systems. Under the same constrained conditions, both the amplitude filters and pure-phase filters are calculated to give their each design parameters. In comparison with those for plane wave, our annular binary filters are better in terms of performances and energy utilization.2. Superresolution theories between uniform amplitude beam and Gaussian beam are compared. Gaussian beam is taken into account to investigate the superresolution phenomenon. Regarding that for uniform amplitude beam has been widely explored for quite a long time; a comparison of superresolution performances between these two types of incident beam would be beneficial. Two commonly-used superresolution filters, amplitude and pure-phase filters, are employed to carry out specific numerical analyses. The simulated results show that the superresolution performances present a strong sensitivity to the type of incident beam. No matter amplitude or pure-phase filter, the intercepted Gaussian beam obtains far superior central brightness ratio and side-lobe effect for the same spot size ratio in contrast with the uniform amplitude beam. In addition, the performances of different filters are rather similar for this type of incident beam.3. The general three-dimensional Gaussian-dependence superresolving theory is given within the second-order approximation of intensity distribution near focus. Furthermore, the amplitude profile of incident Gaussian beam is variable, which could turn from narrow ring to smooth profile (uniform-amplitude). A two-zone annular phase filter is subsequently used to make a quantitative comparison of focusing properties among different shapes of Gaussian beam. Consequently, our investigation can be regarded as a revision to the previous uniform-amplitude based superresolving theory and provide a reference to the practical applications. Of course, if the focusing properties and the shape of incident Gaussian beam are specified, we can also design the structure of the filter by a fitting procedure.4. A new type of superresolution optical pick-up system is presented. The superresolution filter is applied into the optical pick-up system to improve the resolution. Adding an extra filter in the optical pick-up system will definitely bring some new problems. After investigating the structure of superresolution optical pick-up system for a long time, two new structures are presented. Although they still have some disadvantages, these two structures are of great practical benefits.5. Superresolution mastering system is presented. The superresolution filter is applied in the mastering system. After a detailed investigation, the place of filter is fixed. Then the intensity distribution on the focusing plane is simulated with the software Zemax. The simulated results validated our previous conclusions based on superresolution theory regarding Gaussian beam.6. The experiments of adjusting and evaluating the optical readout system are carried out. The adjustment and evaluation are indispensable processes during the production of optical pick-up. Through the experiments the evaluation parameters and devices adjustment are extensively explored, which accumulates much valuable experiences for the future industrialization of the superresolution optical pick-up.