Teddy Fernández, ToneySotillo Buzarra, Beléndel Hoyo, JesúsValles, Juan AntonioMartínez Vázquez, RebecaFernández Sánchez, PalomaSolis, Javier2023-06-182023-06-182015-05-151041-113510.1109/lpt.2015.2407378https://hdl.handle.net/20.500.14352/24035© IEEE (Institute of Electrical and Electronics Engineers). Work partially supported by the Spanish Ministry of Economy & Competitiveness (MINECO, TEC2011-22422, MAT2012-31959), J.H. & T.T.F. acknowledge funding from the JAE CSIC Program (co-funded by the European Social Fund). B Sotillo acknowledges her funding in the frame of CSD2009-00013 (MINECO).Ion migration in high repetition rate femtosecond laser inscribed waveguides is currently being reported in different optical glasses. For the first time, we discuss and experimentally demonstrate the presence of two regimes of ion migration found in laser written waveguides. Regime-I corresponds to the initial waveguide formation mainly via light element migration (in our case atomic weight < 31 u), whereas regime-II majorly corresponds to the movement of heavy elements. This behavior brings attention to a problem which has never been analyzed before and that affects the laser written active waveguides, in which active ions migrate changing their local spectroscopic properties. The migration of active ions may in fact detune the predesigned optimal values of active photonic devices. This letter experimentally demonstrate this problem and provides solutions to avert it.engjournal articlehttp://dx.doi.org/10.1109/lpt.2015.2407378http://ieeexplore.ieee.org/http://arxiv.org/pdf/1412.5783v2open access538.9GlassGainInscriptionFísica de materialesFísica del estado sólido2211 Física del Estado Sólido