Regular and tidy periodic structures hae been directly induced on glasses using a CW CO2 laser beam with linear polarization. It is experimentally shown that precise periodic structures with the period of several microns can be formed by means of well-set laser parameters. The orientation of the periodic structures formed is the same as that of the laser polarization no matter what the scanning direction is. The occurrence of periodic structures is very sensitive to laser power level and scanning velocity. To obtain appropriate periodic patterns, a combined condition of laser energy and scanning velocity must be satisfied. The period, width and height of the structures are dependent on processing parameters. An interesting phenomenon is that the period decreases with increasing scanning velocity. Permanent relieves with periods, widths and heights varied with the laser parameters are also studied.
In this paper, we will describe a new method to fabricate optical diffractive gratings on glass surface with direct CW CO2 laser irradiation. A laser beam with linear polarization was focused and scanned on a glass substrate. The interaction of the beam with the material irradiated results in a periodic ridge structure formation on the substrate under a well-controlled laser irradiation dose. Using multi-path scanning method, with a suitable overlap, diffractive grating with large area can be achieved. In this experiment, laser irradiation dose was 50 J/cm2, laser scanning speed was 0.2 mm/s, the diameter of focused beam was 30 ?m, and the grating period was about 8 ?m.