1.5-micron enhancement in active waveguides fabricated with femtosecond laser pulses

We report on single mode active waveguides at 1.5 mum in Er:Yb-doped glass substrates fabricated with femtosecond laser pulses. A new spatial beam shaping approach for fabrication of waveguides with circular transverse profile is discussed, which uses an astigmatic beam and controls both beam waist and focal position in tangential and sagittal planes. The experimental results are well described by a simple nonlinear absorption model. The waveguides realized with this technique provide a significant enhancement in the whole Er-band, becoming interesting candidates for the realization of many photonic devices.