Guiding and lasing comparison of Nd:YAG waveguide lasers fabricated by femtosecond laser inscription at 515 and 1030 nm

We report the comparative investigation of fabricating type-II waveguide lasers in Nd:Y3Al5O12 (Nd:YAG) using femtosecond laser pulses at 515 and 1030 nm. We focus on the comparison in track morphologies, modification thresholds, and the overall efficiency of the ultrafast laser inscription (ULI) process in creating these waveguides. For both wavelengths, we demonstrated low propagation losses of 0.2 dB/cm. We achieved the lowest reported lasing threshold of 9 mW in a Nd:YAG waveguide laser. Superior performance was achieved with the 1030-nm ULI source, yielding a slope efficiency over 40% and achieving a lasing threshold at half the value observed for the 515-nm source.