Refractive index control of SiO2 films by pulsed laser deposition with silicone targets

We fabricated layered structures of SiO2 films with different refractive indices by pulsed laser deposition with silicone targets. The refractive index of SiO2 films could be controlled by the deposition rate. Lowering of the deposition rate helped to make a dense film, showing higher refractive index. A 0.4-μm-thick SiO2 cladding film deposited at 0.1 nm/pulse was first formed on the entire surface of a Si wafer, and then a 1-μm-thick SiO2 core film was deposited at 0.05 nm/pulse in a line of 1 mm width on the sample. The deposited films were free of impurities such as H2O and carbon. Transparent, tightly layered structures were obtained. The layered structures could also be fabricated on a flexible substrate consisting of a 100-μm-thick polyester sheet. Both samples functioned as an optical waveguide for a 633-nm He-Ne laser. The single-mode propagations were observed as designed.