Chemical Etching Properties Of Micro-structure In Glasses Modified By Femtosecond Laser Pulses

Due to ultrashort time duration and ultrahigh peak fluence, the technology of femtosecond laser machining can realize the non-thermal processing of almost any materials, the workspace is very small and the accuracy is very high, it has been widely used in micro-machining with different materials. The femtosecond laser modificating chemical etching technique has a good prospect in the application of Micro Total Analysis System (μ-TAS) and photonic crystal, but the mechanisms of glass modifying-chemical and how to select suitable materials are both unknown, the paper is based on the study of above mentioned questions.The ablation of three different typical glass (fused silica, tellurite and lead silicate) has been studied using Ti:Sapphire laser pulses at the wavelength of 800 nm, we report the the measurements of the damage threshold and diameter ablation for three different glass, the ablated diameter increases with increasing laser fluence and shot number, and the reason why laser-induced periodic surface structures grow is analyzed.The femtosecond laser modificating-chemical etching technique is used to study the chemical etching character of three different typical glass respectively. The micro-structure development of three samples before and after etching are observed with CCD camera image and scanning electron microscope (SEM). The dependences of etching rate on micro-structure of glasses, pulses energy and etching duration are exhibited. The mechanisms of glass modifying-chemical etching are discussed. The results show: (1) femtosecond laser modified tellurite and lead silicate have no chemical selective etching,but for fused silica the selective etching rate is higher than 50.(2) With the central wavelength of 800nm and the pulse duration of 50fs, when pulses energy is suitable, silica glass can gain the highest selective etching rate. (3) The character of chemical selective etching of femtosecond laser modified glass is largely depends on the matrix local structures, the glass with lager molecule volume has no properties of chemical selective etching, such as tellurite and lead silicate glass.To polish the etched microchannel surface, annealing processing is used. The microstructure of the silica glass and the influence of heat-treatment on the structure and the thermal properties of the glass are investigated according to the CCD camera image. The results show that: when temperature gets very high, silica glass is sensitive to it, crystallization can be investigated; Impurity of glass surface can promote crystallization, for example, the crystallization tendency is markedly higher if the glass is wet.