| Abstract [eng] |
Even though laser micromachining has been investigated by scientists for years, interest of research in the field is still increasing. Recent advances in laser technology enabled machining of micro-nano scale structures employing ultrashort pulses, therefore this particular method is applied for wide range of industrial and scientific applications. Current work describes methods for patterning of microstructures employing lasers as well as discusses laser – material interactions and their parameters. Most popular laser systems and their constructions, operation principles, types, methods and applications are reviewed. The main focus is concentrated on micromachining of aluminum oxide ceramics using femtosecond laser pulses. Since micromachining of materials strongly depends on their properties as well as laser beam parameters, a number of experiments were carried out: determination of focal distance, ablation threshold, micromachining quality and defocusing under different ablation rate, energy density, pulse overlap and ablation cycles count were performed. These experiments enabled obtaining optimal laser micromachining parameters which were used for further formation of more complex microstructures. The surface morphology has been analyzed using optical microscope (“OPTIKA”) and scanning electron microscope (SEM) “FEI Quanta 200FEG”. The depth of microstructures was measured using profilometer (TR200), computer controlled vertical translation stage ANT130-5-V (AeroTech) and monitoring CCD camera view of the sample surface trough a 50x and 0,42 NA microscope objective (Mitutoyo) of the “FemtoLAB” system. The height of the trenches was obtained by subtracting the translation stage coordinates at the focus of non-ablated surface and the bottom of the ablated crater surfaces respectively. During the experiments optimal height of sample with respect to the lens was obtained where laser beam energy is concentrated into smallest area. The ablation threshold of aluminum oxide ceramics was found to be – 1,69 J/cm2. Furthermore, the surface quality after micromachining depends on the pulse overlap and pulse density. Best surface quality was achieved using 84,4 % pulse overlap and 11,2 J/cm2 energy density. Experimentally obtained depth of focus was compared with the theoretical calculations. 9,5 – 19,5 µm variation in height between two ablation cycles was selected for further formation of microstructures because using higher values resulted in reduction of surface quality and formation of recast debris layer. Optimal micromachining parameters were used for formation of 3D pyramids, microfluidic device and scanning acoustic microscope calibration block. |
