Near-field Scanning Optical Technologies And High Density Optical Data Storage

Along with the development of science towards the further microcosmic fields, in many researches such as fluorescence spectrum of single molecule, ultra-fast phenomena study of quanta material, etc., a high time-resolution is not enough, and a high spatial-resolution is needed too. Near-field Scanning Optical Microscopy (NSOM) provides a very high special-resolution beyond the Rayleigh scattering limit, and helps us to obtain an optical resolution of nanometer scale. Therefore, NSOM becomes a powerful tool to explore the nanometer scale structure and spectrum. In this dissertation, the key NSOM technology is studied firstly. A data bus is extended from the parallel port of a computer, and NSOM combines every unit via this data bus to communicate and control the system. The nanometer scanner is a 3-dimension piezo tube. The computer controls the three channel DACs to output different voltage, and the amplified voltage drives the piezo tube to scan with high resolution and the computer can acquire the surface data and optical data of the sample. In NSOM, it is very important to manufacture the fiber probe and control the near-field distance between the fiber tip and the surface of the sample. To the fiber probe, a very small aperture is wanted while a high light transmission is need, and we get the fiber probe by eroding the single mode fiber with HF. In order to control the near-field distance between fiber probe and the sample, a near-field distance sensor is discussed by using high frequency-resolution signal generator Direct Digital Synthesis (DDS), and dual piezo chip. The PI control model is described by the actual distance between the probe and the sample, which is get by non-optic method, and the probe tip is controlled over the sample surface within near-field. After scanning spot by spot, the near-field optical image and surface image are formed. With NSOM the near-field optical storage property of bacteriorhodopsin, a kind of photochromic material, is studied. A green beam is used to write in the bacteriorhodopsin film, and the near-field optical storage isrealized with this film.Near-field optical technology breaks through the diffraction limit, and provides a new idea to high-density optical data storage because of its sub-wavelength resolution. It is available to improve optical storage density by using short wavelength laser, but a harder focusing servo system is need. To focus a beam on the recording media exactly, an experimental precision auto-focusing setup is built. With the astigmatic lens and a quadrant photodetector, the system turns the focusing deviation into focusing error signal, and executes the PI controlling of the distance between the beam focus and the recording media, to insure the beam focus is on the media surface. Finally a ~500nm recording track is realized on the CD-RW disc with the laser source of 532nm. Solid Immersion Lens (SIL) is made by high refractive index glass. SIL can provide the near-field optical resolution with the high transmitted light power, and is considered to be most practically used near-field optical data storage way because of its high speed and density. But to use SIL recording, the problems of the focusing servo and the dynamically flying height control of the SIL must be solved. Here an analog-digital mixed signal IC CXA1372 is used to perform focusing servo. When we focus a beam on the still CD-RW disc through the SIL, a 450nm recording track is obtained after moving the objective lens in the parallel plane to the disc. To control the flying height of the SIL, the height is measured by the capacity between the SIL and the disc, and the SIL fixed in flying head is loaded on the surface of the rotating disc by flexible cantalever. The SIL will fly at different height with the different rotating speed of the disc. When it works, a computer is used to detect the flying height of the SIL, and after comparing this result with the preset value, it controls the disc to accelerate or decelerate, and this will result in adjusting the flying height of the SIL. In th...