Ultra-short Laser Micromachining Of Optoelectronic Materials

Due to its better chemical and thermal stability, GaN wide band gap semiconductor has become an important material of LED optoelectronic devices. Silica fiber material has widely used in optical fiber communications and sensing, and its importance is self-evident. But these two materials are hard and brittle, it's difficult to process by the traditional method. Ultrashort laser (157nm laser and femtosecond laser) because of its small thermal impact is expected to become the ideal for micromachining tools for GaN and fiber materials.Based on this, the research about micro-maching of optical fiber and GaN materials using the157nm laser and femtosecond laser are described in this paper. The mechanism and characteristics of the two kinds of laser is briefly described in the paper. Respectively, in order to study the relationship between the two laser processing parameters and etching quality, we used two lasers on GaN and the fiber material to a series of micro-processing experiment. The main research content and conclusions are as follows:1. The influence of the157nm laser processing parameters on the materials of polishing and cutting quality is investigated. Experimental results show that, in a certain range, the etched surface roughness Ra gradually decreases with the speed of laser scan increases. And, with the increasing of laser repetition rate and the size of laser-spot or with the decreasing of scan shift rate perpendicular to scan direction, the etched surface roughness would increase. In addition, the laser fluence has a great impact to the processing results. Using the157nm laser, experimental of cutting on GaN materials is conduct. The defocus amount impact on the width and depth of kerf is analysed, adopting different ways of maching to test, and finding a best way to process.2. Using femtosecond laser, experimental investigations of polishing and cutting on GaN-LED semiconductor films are carried out, discussing the relationship between processing parameters and ablation quality. Experimental results show that, with the increasing of the pulse energy and the time of scans, the results of micro-plane processing are poor. But the scan shift rate perpendicular to scan direction has not a clear impact to the results. During the whole test of cutting, with the increasing of the pulse energy and with the decreasing of the speed of laser scan, the depth of kerf would increase. Besides, the width of kerf would decrease when the number of pulse reduces and the speed of laser scan increase.