Femtosecond Laser And Transparent Crystal Micro Machining Mechanism And Feasibility Studies

Recently, because of the unique characteristics of femtosecond laser ablate transparentmaterials, using femtosecond laser to transparent materials become the focus of people widelyconcern about. People are more focused on researching the interaction between femtosecondlaser and some materials such as glass, quartz, crystal. Research on the damage threshold andmicro-machine of traditional crystals such as Iceland spar, mica, has been little report. Andparticularly there are many technical issues of Mica material cutting and drilling, which severelyconstrain this high quality optics of birefringent material to use. So, research the interaction offemtosecond laser and mica crystal has very important practical significance. This researchproject also has received financial support from the provincial authorities.In this dissertation, parts of theoretical and experimental studies on using femtosecond laserto micro-machine mica crystal are presented. The main contents are classified as follows.(1) The research status of using femtosecond laser to micro-machine transparent materials isintroduced briefly. The physical mechanism of transparent materials ablated by a femtosecondlaser pulse is summarized, which focused on the ionization processes of multi-photon ionizationand avalanche ionization. The relation between damage threshold and laser pulse duration,photon energy is studied.(2) Damage thresholds of different thickness of the mica materials are measured under thefemtosecond laser. The relationship between thickness of material and damage threshold isstudied. Multi-photon ionization mechanism of the femtosecond laser interact with transparentmaterials is verified, which is not directly related to the thickness of the sample, and only thenature of the material itself is related. These laid foundation for researching the femtosecondlaser micro-machine mica crystal.(3) The research of experiment that using femtosecond laser to micro-machine mica crystals,attempting to make some microscale experiment devices. A detailed comparison of advantagesand disadvantages of the process between the femtosecond laser hole machining and thetraditional mechanical hole machining.The main innovations in this dissertation are classified as follows.(1) The view of damage threshold point is judged by the emergence of the sudden change intransmittance is proposed in first time. According to this method, damage thresholds of micacrystal with thickness ranged from45μm to138μm are measured accurately under thefemtosecond laser. The result indicates that damage threshold of mica irradiated by femtosecondlaser with a specific pulse width is not directly related to the thickness of the sample, and onlythe nature of the material itself is related. (2) The process of using femtosecond laser to machine hole in the mica materials arestudied simple. The results of experimental show that it has incomparable advantages comparedto the process of traditional mechanical hole machining.Using femtosecond laser to the machinemicro-mica wave plates with diameter as short as a few hundred micrometers. And this providesan important reference for the future application of the miniaturization of the mica material.