Optical waveguides fabricated in Cr:LiSAF by femtosecond laser micromachining

In this work we present the fabrication of double-track type II waveguides written in 1% doped Cr:LiSrAlF6 (Cr:LiSAF) crystal by femtosecond laser micromachining. We studied waveguides fabricated at energies from 1 to 7 mu J per pulse at writing speeds of 1545 mu m/s. We found good wave-guiding performance for both, Transversal Magnetic (TM) and Transversal Electric (TE) polarization modes as well as acceptable losses according to the expected values addressed to technological applications. Also, we performed a high-resolution mu-luminescence waveguide cross-section mapping between the tracks, in order to identify possible spectral changes caused for active ions Cr3+ corresponding to the T-4(2) -> (4)A(2) vibronic transition in the focal volume zone, due to induced anisotropic graded stress. Finally, their lifetimes were measured for bulk as well as for waveguide trapped ions. We found that for the range of parameters of ultra-short micromachining used, the Cr3+ ions embedded in the waveguides remained spectroscopically unchanged compared with those observed in bulk material. (C) 2017 Elsevier B.V. All rights reserved.