Abstract

In this paper, we report on the ultrafast laser-induced birefringence, refractive index changes, and enhanced photoluminescence properties in the volume of neodymium (Nd), yttrium (Y) co-doped strontium fluoride (${\mathrm{SrF}}_2$) and Nd, Y co-doped calcium fluoride (${\mathrm{CaF}}_2$) crystals. The optical waveguides written with 500 kHz repetition rate provided lowest propagation loss of $1.63\pm 0.21\mathrm{dB}{\mathrm{cm}}^{-1}$ for transverse magnetic (TM) polarization at 632.8 nm in $\mathrm{Nd},\mathrm{Y}\text{:}{\mathrm{SrF}}_2$ crystal. The measured retardance can be interpreted by stress-induced birefringence related to the permanent volume expansion, photo induced by a non-spherical irradiated zone. The absorption, steady-state, and time-resolved photoluminescence properties are also carried out in and out of the laser irradiated zone, enabling the local changes of the Nd and Y network in $\mathrm{Nd},\mathrm{Y}\text{:}{\mathrm{SrF}}_2$, as well as well-preserved Nd fluorescence in the written optical waveguides.

© 2019 Optical Society of America

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