Research On The Interference Nanosecond Laser Ablation Of Micro-grating Structures On The Silicon Surface

The fabrication of micro-grating structures (MGSs) is a hot topic in the field of Microfabrication. As the period of grating is very small, the cost is expensive, and technical is difficult, it is still hard to achieve the mass production of MGSs in industry. In this thesis, the MGSs were fabricated on the silicon wafers using the interference nanosecond laser pulses. The related experiments and tests have been done.Generally, the following items are included in this thesis.Firstly, the analytical methods for the researches on MGSs were introduced. Based on the theory of Rigorous Coupled Wave Analysis (RCWA), the formulas for the calculation of MGSs'diffraction efficiency were carried out. And MGSs'models were designed and simulated by a tool called DiffractMOD of Rsoft software.Secondly, diode-pumped solid-state laser (DPSSL) was used as the light resource, and beam split by kinds of phase gratings, the system for multiple beam of nanosecond UV laser ablation was built. During the experiments, the MGSs were ablated on silicon wafer directly.Thirdly, one dimensional grating was ablated by dual-beam interference. The period of the grating is 0.55μm. The reflectivities of samples were measured, which were ablated by different numbers of pulses. And the results showed that the anti-reflection structure was effectively made on Si.Fourthly, two dimensional cross grating were ablated in the experiments using 4 lasers beam interference. The period of grating is 1.25μm. The experimental parameters and samples were analyzed. The factors that influence the results were discussed. This kind of periodic structure can be applied in the field of photonic bandgap crystals and bioscience, etc.In summary, this thesis presented a novel method for MGSs'fabrication. It simplifies the working procedure, and enhanced the efficiency. The microstructure on the surface of silicon was changed, and the light utilization of silicon was optimized. This research extends the application of high power laser ablation in the field of Microfabrication. It has been widely prospected and valued for both industry and science.