Interaction Of Femtosecond Laser Pulses With Transparent Materials And Its Applications

An intense femtosecond laser pulse can provide an electric field strength which exceeds the electric field force of valance electrons that holds the electrons to their ionic cores. Compared with picosecond, nanosecond laser pulse, a femtosecond laser pulse shows excellent advantages such as little or no thermal affected zone, the break of optical diffraction limit and space-selection. Based on those virtues, femtosecond laser pulse can be used many fields, for example, ultra-precision machining, the fabrication of micro- photonic devices, nano-operation in bioengineering and biatrology, and three dimensional optical storage. This thesis ranges over Ti:sapphire laser techniques and frequency conversion, Ti: sapphire regenerative femtosecond amplification and its applications. And the thesis is focused on the mechanism of refractive index changes of fused silica induced by femtosecond laser pulse, and resulting applications such as three dimensional optical storage, the fabrication of grating and waveguide.About Ti:sapphire laser techniques and frequency conversion, the optimum design about the parameters of oscillator and nonlinear crystals was investigated, and the compensation for thermal effect coming from nonlinear crystal and elements in oscillator. Then a Ti:sapphire femtosecond amplifier without stretcher using for micro- machining and optical storage was built. The stretch of seed pulse resulting from the components dispersion in cavity, the off-focusing Ti:sapphire crystal and TEMoo mode pumping laser contribute to a compact, efficient regenerative amplification.In femtosecond laser micro-machining, the dependence of the refractive index changes on the laser parameters was investigated theoretically. A micromachining system has been built. The writing and reading of bits in parallel and bit-by-bit are demonstrated in 3-dimension in transparent materials with fs laser pulse. The writing of an internal diffraction grating and waveguide in optical glass plate is demonstrated using low-density plasma formation excited by a high-intensity femtosecond Ti:sapphire laser, birefringence in those elements, and vaporization and re-crystallization of anisotropy crystal material were observed in the process of micro-explosion due to the expansion of high temperature plasma.