Reduction of thermal effects in a 2.7-µm Er:Y₂O₃ ceramic laser with annular pumping

Reduction of thermal effects is a challenging aspect for power scaling of 2.7-µm bulk Er-lasers due to the large quantum defect when pumping at ∼ 0.97 µm. Here, we demonstrate that thermal effects in an Er:Y₂O₃ ceramic laser can be significantly reduced pumping by an annular beam, thus improving the continuous-wave (CW) laser performance in the 3-µm spectral range. The excitation conditions of the TEM₀₀ mode were determined theoretically by taking into account the propagation characteristics of the annular pump beam. For a comparison, the temperature and stress distributions are at first theoretically studied with three different pump configurations. In the experiment, output power of the Er:Y₂O₃ ceramic laser improved by ∼ 60% by changing the pump beam from coventional quasi-top-hat to a designed annular one. This work, as a proof-of-principle study, indicates the potential of power scaling of the 2.7-µm bulk Er-lasers pumping with an annular beam.