Damage-Induced Refractive Index Changes And Associated Waveguide Mode Study In Ion Implanted Optoelectronic Crystals

A waveguide is characterized by a region of high refractive index bounded by regions of lower index. It can confine the optical energy in small space and improve the optical energy density. Waveguide is the basic component of integrated optics, and it also plays an important roll in the manufacture of optical devices. Because of its importance in practical application, scientists and engineers are trying to find various ways to fabricate "high-quality" optical waveguide. Several waveguide fabrication techniques have been developed to obtain the waveguide structures, such as metal diffusion, ion exchange, thin film deposition and ion implantation.Recently ion implantation, as an outstanding method to modify the surface property of materials, confirms it to be a universal method for fabricating waveguide structures in most optical materials because it has a superior controllability and reproducibility. In the waveguides formed by light-ion implantation, such as He or H, ion dose of order of 10¹⁶ ions/cm² or higher are needed, an optical barrier has been built up at the end of the track due to the damage induced by nuclear energy loss. Such an optical barrier confines the light in an "optical well" between itself and the surface. And in some waveguides formed by He⁺ implantation, positive refractive index changes are observed in the waveguide region. More recently, many results show that heavier ion implanted waveguides may be fabricated efficiently in optical; materials because much lower doses (10¹³-10¹⁵ ions/cm²) are needed. In the...