| 摘要 |
PURPOSE:To provide the three-dimensional optical waveguide which has a flat surface, has a staircase refractive index distribution and is independently controlled in width and thickness by setting the thickness of a dielectric crystal thin film of parts exclusive of a groove part smaller than an optical waveguide cutoff thickness and setting the thickness of the dielectric crystal thin film of the groove part larger than the optical waveguide cutoff thickness. CONSTITUTION:The thickness d1 of the LiNbO3 thin film 2 of the parts exclusive of the groove 1a is set smaller than the optical waveguide cutoff thickness and the thickness d2 of the NiNbO3 thin film 2 of the part of the groove 1a is set larger than the optical waveguide cutoff thickness. Only the LiNbO3 thin film 2 of the part of the groove 1a is thereby provided with an optical waveguide function. The optical waveguide cutoff thickness dc.o.TE of a TE mode is determined from equations I, II and the optical waveguide cutoff thickness dc.o.TM of a TM mode is determined from equations III, IV. In the equations I to IV, ns, nr, nc are respectively the refractive indices of the substrate 1, the LiNbO3 thin film 2 and the clad layer and ko=2pi/lambda (lambda is the wavelength of the light in vacuum). |
