A new method to suppress the cladding-mode coupling loss in fiber Bragg gratings, by independent control of the core refractive index profile and the photosensitive profile, is proposed and experimentally demonstrated. Across the core and the inner cladding, a uniform step photosensitive profile was introduced by co-doping GeO2 and B2O3. The core refractive index was selectively raised by further doping Al2O3 in the core that has negligible photosensitivity 244 nm. For strong Bragg gratings inscribed on the fiber, the cladding-mode coupling loss was suppressed below 0.3 dB.
Bibliographical noteFunding Information:
Manuscript received April 3, 2000; revised July 6, 2000. This work was supported in part by UFON, the ERC Program in K-JIST, and by the BK21 Project sponsored by MOE.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Atomic and Molecular Physics, and Optics
- Electrical and Electronic Engineering