| 摘要 |
Reflective mode coupling refractive index gratings are disclosed. The gratings can couple light of wavelength lambda i in a fundamental spatial mode of the waveguide (e.g., LP01) to a reflected higher order spatial mode (e.g., LP11), substantially without reflection of any light of wavelength lambda j NOTEQUAL lambda i in a spectral range DELTA lambda APPROXLESS 0.01 lambda i. The mode coupling gratings (MCGs) can find a variety of uses in optical fiber systems. Exemplarily, an MCG can serve as a wavelength-dependent loss element with abrupt (e.g., SIMILAR 1 nm) spectral dependence. However, a chirped grating with or without strength modulation can yield an MCG having relatively wide spectral dependence, including variable loss over a relatively wide (e.g., SIMILAR 10 nm) spectral range. Both types of MCGs are advantageously used in, for instance, optical waveguide amplifiers. |
