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Highly transparent Y 2 O 3 ceramics were successfully fabricated with CaO as sintering aid. The microstructure evolution, optical transmittance, hardness and thermal conductivity of the Y 2 O 3 ceramics were investigated. It was found that doping a small amount (0.01-0.15 wt.%) of CaO could greatly improve the densification rate of Y 2 O 3 . With an optimized CaO dosage of 0.02 wt.% combined with the low temperature vacuum sintering plus hot isostatic pressing (HIP-ing), Y 2 O 3 ceramics with in-line transmittance of 84.87% at 1200 nm and 81.4% at 600 nm were obtained.

We demonstrate, to the best of our knowledge, the first direct vortex beam generation in the 3 μm spectral region by employing an Er:Y 2 O 3 ceramic laser. Controllable handedness with high purity is achieved by introducing asymmetric cavity loss and reducing the number of longitudinal modes. The average orbital angular momentum of the produced scalar vortex beam is quantitatively evaluated to be 0.95ħ for the LG 0,+1 mode and -0.94ħ for the LG 0,-1 mode. The corresponding optical spectrum is centered at 2710.8 and 2710.5 nm, respectively.