Fabrication of Internal Gratings in PDMS Using a Femtosecond Laser

Photo-induced gratings in flexible PDMS (polydimethly siloxane) film are directly written by a high-intensity femtosecond (130fs) Ti: Sapphire laser (λp = 800nm). The refractive index modifications with 4 μm diameters were photo-induced after the femtosecond irradiation with peak intensities of more than 1 × 1011W/cm2. The graded refractive index profile was fabricated to be a symmetric around the center of the point at which femtosecond laser by controlling both laser power and focused depth. The change on refractive index in the laser-modified regions was estimated to be approximately 10-3. The internal flexible symmetric diffraction gratings in PDMS film was successfully fabricated using a femtosecond laser.