Experimental and theoretical explorations for optimizing high-power geometric modes in diode-pumped solid-state lasers

The variation of transverse patterns on the cavity length is experimentally explored by using an off-axis pumped Nd:YVO₄ laser to identify the range of the length for generating geometric modes (GMs). Using the inhomogeneous Helmholtz equation, it is theoretically confirmed that the stable range of the cavity length for generating GMs can be significantly enlarged by decreasing the output reflectance. Furthermore, experimental results reveal that the cavity length for scaling up the output power of GMs must be shortened due to the thermal lensing effect in the gain medium. Considering the balance between the output efficiency and the stable range of the cavity length, the optimal output reflectance is verified to be approximately 80%. With the optimal output reflectance, the average output power of GMs can be up to 6.33 W at a pump power of 12 W.