Three-dimensional Optical Storage Inside Transparent Materials Using Femtosecond Laser Pulses And Generation And Detection Of THz Radiation Pulse

This thesis includes two parts: the study of three-dimensional optical storage inside transparent materials using femtosecond laser pulses and the study of generation and detection of THz radiation pulse.An intense laser pulse with nJ energy, 800nm, 150-fs at repetition rate of 1-kHz is tightly focused inside the transparent material, inducing the energy of pulse absorbed by material, leaving a permanent structure changes with sub-micrometer precision in the material. The size of the structure increases with the energy of laser pulse—from small density variations to voids. The array of these voids in different layers is localized inside the bulk of the material, three-dimensional optical storage is recorded inside the sample.In the first part of this thesis, the main aim is to study experimentally some difficult problem in three-dimensional high-density optical storage in transparent materials using femtosecond laser pulse. The context and conclude is summarized as follow:(1) It is set up a system to write and read, including a software system and a hardware system.(2) The nonlinear interaction of fs laser and transparent materials is discussed. It is investigated the bulk structural change morphology inside transparent materials induced by tightly focused fs laser pulses. Some kinds of structure changes (from small density variations to voids) is introduced.(3) The writing and reading of bits (one layer or many layers) in parallel and bit-by-bit are demonstrated in three dimension in transparent materials with fs laser. The storage volumetric density is 500G/cm3, the capability of this kind storage device with the same area as CD is several orders larger than that of a CD.In the second part of this thesis, the main aim is to study the generation and detection of THz radiation pulse.We introduced two ways to generation THz radiation pulse: photoconductive method and optical rectification method. The woks point out that the physical essence of generation of generation of THz radiation pulse is a second polarization process.We also introduced two ways to detect THz radiation pulse: photoconductive sampling detection and electro-optic sampling detection. The theoretical basis and the experimental setup of THz detection is analyzed' and described systematically, especially for electro-optic sampling detection.