| 摘要 |
PCT No. PCT/GB90/01917 Sec. 371 Date Jun. 24, 1992 Sec. 102(e) Date Jun. 24, 1992 PCT Filed Dec. 7, 1990 PCT Pub. No. WO91/09338 PCT Pub. Date Jun. 27, 1991.An optical waveguide in which the rate of change with wavelength of the reciprocal of the difference between the effective refractive indices of a fundamental wavelength mode and a second harmonic wavelength mode is zero at a first wavelength, and there is an internal periodic grating providing phase matching in the wavelength region of the first wavelength.
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