| 摘要 |
Optical communications networks may be implemented by means of a patterned layer of an optically transparent material on a substrate. Where an optical path terminates, e.g., at an on-off switch, it is desirable to optically terminate a waveguide so as to minimize spurious signals due to reflection. The invention provides for optical termination of a waveguide by essentially complete absorption of light. Absorption is effected in a portion of the waveguide which comprises light absorbing centers such as, e.g., carbon or metal particles, anions, cations, or molecules which absorb light at desired wavelengths. Absorbing centers may be comprised in a central portion of a waveguide or, more conveniently, in a portion adjacent to a central portion. In the interest of minimizing reflections, interaction between light and absorbing centers increases gradually in a direction of light propagation as may be due to gradually increasing concentration of absorbing centers or to taper in a waveguide cladding portion, core portion, or absorbing portion.
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