| 摘要 |
A width of a core in an optical waveguide is decreased in accordance with a predetermined value, as a distance of a position of the core to the centre position thereof is decreased. Consequently, a rectangular spectrum property having no ripple is obtained on a lower wavelength side in a reflection grating. In addition, the width of the core is changed at the position Z in the direction of light propagation, while UV light is radiated to the core, so that a periodically-striated distribution of refractive indices having an envelope which is changed in accordance with a value of "¦sin(C~Z)¦/¦C~Z¦" is formed in the core of the optical waveguide, and the phase of light to be propagated in the direction of light propagation is shifted at the position Z as defined below by .pi.. Z=m.pi./C(m=...,-3,-2,-1,1,2,3,...) Thus, a rectangular spectrum property is obtained in a low-reflection grating. |
