| 摘要 |
PURPOSE:To precisely set the depth of etching to realize desired transmission characteristics by diffusing a doping agent into a substrate to form a light guide layer satisfying prescribed conditions, and etching the substrate down to a prescribed depth to form a clad layer. CONSTITUTION:A doping agent, such as Ti, is diffused into a substrate, such as a Y-cut plate of LiNbO3 to form a light guide layer having a Gauss type refractive index distribution n(x), and then, the substrate is etched down to the depth d from the surface by using a ion milling device to form a ridge type light guide, and further, it is coated with a cald layer, such as Si3N4 film, having a refractive index of n3. The depth (d) is decided from formula II by using beta satisfying formula I fulfilling single mode conditions, where n(x) is the refractive index at a depth of x, n1, n2 are each the refractive index of the substrate and the surface of the light guide, respectively, and n(x)=(n2-n1)f(x)+n1, f(0)=1, f(infinity )=0, k=2pi/lambda, and lambda is wavelength. |
