Study Of The Technologies Of High-density Optical Data Storage With Short-wavelength Laser Source And Solid Immersion Lens

The technology of optical data storage is playing a more and more important role in our information society. It is necessary to imploit higher-density optical memory system with the development of data storage technologies. The high-density optical data storage technologies based on short-wavelength laser source and solid immersion lens are studied with the aim to develop the key technologies of the two optical data storages system.In this thesis, the history and the recent advances of high-density optical data storage are summarized firstly. Then, an experimental setup of optical storage system is built up, using a non-sphere colophony object lens with NA=0.65 and green light source with wavelength of 532nm. The system can focus the light beam in sub-micron meter scale, detect the focusing distance error and control the object lens to move to realize automatically focusing. Using phase-changing disc CD-RW as optical storage media, an optical storage experiment carries out with the system and the results shows that a recording track with the width of ~ 500nm is obtained. A Penta Methyl Crynine dye polymer film is made by spin- coated method, and the property of the film is studied with the system at room temperature. Finally a result of about 600nm recording line width on the film is obtained. The above results show that the basic optical writing function is provided with this optical storage system of green light source. At present most research about this are summarized within our country while our works are based on experiment.Using Solid Immersion Lens (SIL) is another method to realize near-field optical data storage. Here with a basic optical system of SIL, a static SIL optical storage system is built up, and a result of ~450nm recording track is obtained on CD-RW disc. Compared with the same system without SIL, the width ratio of recording track is1:1.44. Also a device that can control SIL to fly at a certain height to the surface of recording media is designed. The flying height of SIL is measured by the capacity between the SIL and the disc, and a computer controls the disc to accelerate or decelerate, to adjust the flying height of the SIL. And then, the SIL flying height can be controlled. The related works have not been reported within our country till now.A project that using the solid immersion lens to focus the femtosecond laser pulses in three-dimensional optical data storage is first proposed. The relationship between the actual focusing position and the numerical aperture with the distance of defocusing is calculated. Three-dimensional optical data storage is achieved in PMMA and fused silica by combining 800nm, 150fs laser pulses with NA=0.55 objective lens and solid immersion lens. A theoretical high-density storage as 1.1 x 10 bits/cm in fused silica is achieved. Such result is the highest writing density in transparent materials that is reported at present time.Besides, three component optical fields intensity of focused linear polarized gauss beam in the focal plane and the intensity patterns in the sections of various distance from the focal plane are simulated using three-dimensional finite-difference time-domain (FDTD) method. The results show that the image pattern in the focal plane or the sections near the focal takes on approximate ellipse, while the patterns in the planes of far region displays asymmetrical round. It may be possible to have some theoretical directing in solid immersion lens near-field data storage.