Evanescent-field amplification in Nd³⁺-doped fluoride planar waveguide

Planar channel waveguides of rare-earth doped fluoride glass are demonstrated with single mode excitation and propagation losses below 3 dB/cm. The waveguide core was fabricated by Ag⁺-Na⁺ molten salt ion exchange process in a borosilicate glass (BGG31), and a Nd³⁺-doped ZBLAN glass was used as a cladding. A 0.45 dB signal amplification at 1.064 μm was observed in the fabricated 1 cm long waveguide, and a 0.9 dB amplification is expected at the emission peak (1.049 μm). Modeling results show 2.5 dB/cm potential gain with the improvement in surface flatness of ZBLAN glass.