Er:Yb-doped oxyfluoride silicate glass waveguide amplifier fabricated using femtosecond laser inscription

The authors report net gain from a channel waveguide fabricated in an Er:Yb-doped oxyfluoride silicate glass substrate using femtosecond laser waveguide inscription. To fabricate waveguides exhibiting low propagation and coupling losses, they used the recently demonstrated multiscan technique that allows the waveguide cross section and refractive index contrast to be controlled independently of each other. By doing so, the best waveguide exhibited a total background insertion loss, excluding absorption, of only $1.2\mathrm{dB}$ at $1537\mathrm{nm}$ . As a result, a fiber-fiber net gain of $0.72\mathrm{dB}$ at $1537\mathrm{nm}$ was measured for a $10\mathrm{mm}$ long waveguide.