Lasing in femtosecond laser written optical waveguides

The paper reviews our research efforts in femtosecond laser inscription of optical waveguides inside active Er:Yb-doped glass substrates and in the development of compact waveguide lasers. By optimising the fabrication parameters we obtain waveguides with coupling losses to standard telecom fibers as low as 0.1 dB/facet and propagation losses lower than 0.4 dB/cm. The waveguides provide net gain, with a peak value of 7 dB, and laser action in the whole telecommunications C-band (1530–1565 nm). Single-frequency operation with output power up to 50 mW and passive mode-locking are demonstrated, making the systems useful as compact telecom transmitters. Our results show that femtosecond laser writing can produce high-quality photonic devices, with performance comparable to or better than that obtainable with conventional waveguide fabrication techniques.