A semi-weakly confined erbium-doped waveguide amplifier with double-layered buffer/cladding

A semi-weakly confined waveguide structure was designed and fabricated. This waveguide structure has a 350 nm thin core layer. Its optical mode field is weakly confined in vertical direction but is strongly confined laterally. The waveguide can support a nearly circular optical field distribution that matches well with a single-mode fiber. An erbium-doped waveguide amplifier (EDWA) with the new waveguide structure was fabricated by sol-gel method. The EDWA has a passive core and double-layered buffer/cladding. A small coupling loss of 0.4 dB/facet and an internal gain of 1.9 dB via evanescent wave amplification near 1550 nm were obtained.