| 摘要 |
A waveguide, such as an optical fiber waveguide for guiding light waves, which can provide a strongly reflective grating (e.g., a Bragg grating) at a specified wavelength while maintaining very low losses at adjacent wavelengths. The waveguide includes a core, an inner cladding laterally surrounding the core, an outer cladding laterally surrounding the inner cladding, and a grating pattern. The core has a refractive index nco and a first transverse dimension 2A. The inner cladding has a width W and a refractive index nic. The outer cladding has a refractive index noc. The relation between the refractive indexes, nco>noc>nic and 0.5<A/(A+W)<1, define a narrow depressed well region for limiting cladding losses.
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