Patent ID: 6483955
Filing Date: 2002-11-19
Classification: G02B

Abstract:
A diffraction grating device having a refractive index modulation formed in an optical waveguide region in a predetermined region in a longitudinal direction of an optical waveguide, wherein an optical period of the refractive index modulation is substantially constant, a phase of the refractive index modulation is inverted at a phase inversion portion, the number of phase inversion portions present in the predetermined region is one or two, andwhen z is a variable representing a position in the longitudinal direction using a barycentric position of the predetermined region as an origin, that is, z is an optical distance from the origin, &Dgr;n(z) is an amplitude distribution of the refractive index modulation, and a sign of the amplitude distribution &Dgr;n(z) is changed at the phase inversion portion, parameters A0, A2, B0, and B2 obtained by integral calculations in the predetermined region are given by A0=âˆ«&Dgr;n(z)dz A2=âˆ«z2Â·&Dgr;n(z)dz B0=âˆ«|&Dgr;n(z)|dz B2=âˆ«z2Â·|&Dgr;n(z)|dz and for the parameters A0, A2, B0, and B2, a condition given by &LeftBracketingBar;A2&CenterDot;B0A0&CenterDot;B2&RightBracketingBar;<0.25holds.