Surface subwavelength structure and photonic device fabrication with temporally tailored multiple femtosecond laser pulses

摘要

We have demonstrated the nanostructure fabrication on the Si surface by a 150 fs, 800 nm femtosecond laser pulse. The nanohole size of about 100 nm can be formed presumably by a near-field optical enhancement effect induced by the particle illumination. The nanohole size is nearly independent of the irradiated pulse number. It is found that the optical enhancement factor was about 7 in this experiment. The hexagonally arrayed nanoholes were fabricated. The diameter of the fabricated nanohole was about 90 nm and the depth was about 9 nm. In addition, using the double pulse fs laser, we demonstrated a low-loss waveguide fabrication in fused silica. A low-optical-loss waveguide is fabricated under the conditions that the first pulse energy and the second pulse energy in the double pulse mode are 30 nJ and 160 nJ, respectively, and the 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 new femtosecond double pulse fabrication technique will be very promising for low-loss photonic device fabrication for photonic networks.