Optical waveguide fabrication with double pulse femtosecond lasers

Abstract

We demonstrate the optical waveguide fabrication inside fused silica glasses using double pulse femtosecond lasers to decrease the optical loss which may be caused by nonuniformity of the refractive index change in the modified volume. The pulse separation time of the double pulses is varied from 500fsto200ps. An optical loss of less than 0.8dB∕cm is obtained under the conditions that the first pulse energy and the second pulse energy in the double pulse mode are 30 and 160nJ, respectively, and pulse time interval is 3ps. The weak first pulse would act as a pre-conditioner of the fused silica and then the second subsequent pulse effectively induces the uniform refractive index change. This optical loss is less than 1.3dB∕cm for the waveguides fabricated using a single 160nJ pulse femtosecond laser.