Optical waveguide fabrication with double pulse femtosecond lasers

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 500 fs to 200 ps. An optical loss of less than 0.8 dB/ cm is obtained under the conditions that the first pulse energy and the second pulse energy in the double pulse mode are 30 and 160 nJ, respectively, and pulse time interval is 3 ps. 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 1.3 dB/ cm for the waveguides fabricated using a single 160 nJ pulse femtosecond laser. (c) 2005 American Institute of Physics.