Patent ID: 6021239
Filing Date: 2000-02-01
Classification: G02B,Y10S

Abstract:
A photocoupler, comprising:an optical waveguide including a substrate, at least a first dielectric layer provided on the substrate, the first dielectric layer having a tapered structure whose thickness varies in an x-direction in which light is propagated after coupling, and a second dielectric layer provided on the first dielectric layer;a light incidence component provided above the optical waveguide, which causes light incident thereon to be directed toward a surface of the optical waveguide at a prescribed angle; anda bonding section for bonding the light incidence component to the optical waveguide,wherein the bonding section has an edge surface which makes contact with the surface of the waveguide in a straight line and has a portion which makes contact with neither the light incidence component nor the surface of the optical waveguide; andthe tapered structure of the first dielectric layer has a shape set such that a radiation pattern of light with a wavelength .lambda. output from the optical waveguide of the photocoupler fulfills the following expression (1):a.sub.n-1 (1-r.sub.n)<a.sub.n (1-r.sub.n+1) expression (1)where .sub.m is a radiation coefficient at a section X.sub.n-1 <X<X.sub.n of the first dielectric layer where a thickness thereof varies in a tapering manner; a.sub.n is an amplitude at a distance X.sub.n from the edge surface of the bonding section; and r.sub.n is exp(k.sub.o rn .DELTA.X); k.sub.o is 2.pi./.lambda.; and .DELTA.X is X.sub.n -X.sub.n-1 ; andwherein:a.sub.n-1 is the amplitude at a distance X.sub.n-1 from the edge of the bonding section,r.sub.n+1 =exp(k.sub.o r(n+1) .DELTA.X),r(n+1) is a radiation coefficient at section X.sub.n <X<X.sub.n+1, andX.sub.n+1 =X.sub.n +.DELTA.X.