The Surface-Relief Grating Produced by Interference of Femtosecond Laser

Since the generation of the femtosecond laser, the interaction between femtosecond pulsed laser and metal films has been extensively investigated. There are many peculiar merits of the femtosecond pulsed laser, such as precise control of micromachining sizes and minimized thermal damage to the surroundings. As we all know, a surface-relief grating can be widely applied in holographic data storage, optical communication, optical information processing and optoelectronic industry. Because the absorption coefficient of the silica glass is very low and the small nanojoule fluence of femtosecond Ti:sapphire laser oscillator, it’s difficult to micromachine the surface-relief grating on the silica glass by femtosecond Ti:sapphire laser oscillator. However, in this paper we made the surface-relief grating on the silica glass by using the intereference technique of femtosecond laser with the silica glass coated a chromium films. The optical absorption coefficient of the chromium films is much higher than that of the silica glass. So the heat energy absorbed by the chromium films should be the energy source for inducing the surface-relief grating on silica glass. Experimental results shown that this micromachining technology is simple and effective. It is helpful for us to understand the mechanism of the interaction between the femtosecond laser and chromium films.