The Research Of248nm Excimer Laser Interaction With Three Kinds Of Inorganic Nonmetal Optical Materials

Laser ablation is a promising materials processing and experiment analysis tools,but its mechanism of laser-material interaction involved is not yet clear to understand.This paper researches on excimer laser of nanosecond pulse irradiating glass, singlecrystal Si, diamond thin film etc materials, changing the incident laser frequency,energy, pulse number and experimental environment (atmospheric and vacuum), withthe help of the1-on-1and S-on-1experiment method, employing plasma flash,optical microscopy, water vapor and scanning electron microscope method todetermine the injury and observe the morphology. For the diamond film damageexperiment, plasma flash method cannot be used to determine whether there is injury,but optical microscopy and scanning electron microscopy can be determined,researches the irradiation damage mechanism of the three kinds of materials, finds thedamage threshold of each material, and provides a reference for the preparation ofsubsequent materials which resist to laser damage.After a lot of repeated experiments, it can be summarized: comparingatmospheric and vacuum environments, laser damage threshold of the material isdetermined. For the three kinds of optical materials, as the laser energy is increased,the surface damage will occur. Glass (slide glass) has a chance to be damaged whenthe laser energy ranges from40mJ to100mJ, monocrystalline silicon is20mJ-28mJ,and diamond film appears minimal visible damage when the energy is4mJ. Obtainedfrom the experiments and mathematical calculations, the laser focus spot center areais about0.2mm2, corresponding the damage threshold to the three kinds of opticalmaterials, glass20-50J/cm2, monocrystalline10-14J/cm2, diamond film2J/cm2. Whena single pulse, corresponding damage threshold to the three kinds of material tends tomaxima in the threshold range; when multi-pulse, the damage threshold tends to aminimum. In the multi-pulse conditions, changing the pulse laser frequency from1Hzto3Hz, analysis of the experimental results show that at a certain laser energy, thenumber of pulses damage glass or single crystal silicon is not significant change asthe pulse frequency increases. Observing by optical microscopy and scanning electron microscopy, the ablationcrater’s overall morphology on the three kinds of material’s surface is similar toelliptic shape, which is due to the incidence laser and the target surface normalformed an angle of30°. Many frozen ripples appear around the silicon and glass’sablation crater edge, silicon appears regular ripples, glass irregular, both ablationcrater has cracks, the cracks and ripples is due to uneven intensity distribution of thelaser beam, the incident laser shock and plasma recoil; The ablation area’s color of thediamond film become black, under the action of the laser, diamond happened"graphite change", sp3hybridized C atoms change into sp2hybridized. Laser damagethree kinds of material is a common action of photo-thermal mechanism andphotochemical mechanism. Excimer laser is not only melt, vaporize the material, alsowill destroy the chemical bonds between atoms in material, and decompose thematerial. Comparative analysis of the three materials from their optical properties andstructure, in glass and diamond thin film photochemical mechanism is more obvious,in monocrystalline silicon photo-thermal mechanism is more obvious.