Exploring the elevated Nd:YVO₄ temperature for reaching the second threshold condition of the Cr⁴⁺:YAG passively Q-switched laser

The temperature-dependent second threshold criteria for the Nd:YVO₄/Cr⁴⁺:YAG passively Q-switched (PQS) laser is explored. The emission cross section of the Nd:YVO₄ crystal is found to decrease as temperature elevates, which is feasible to reach the PQS second threshold with a flexible cavity design. We derive theoretical analysis and experimentally verify it by demonstrating the cavity mode size ratio variation between those on the gain medium and the saturable absorber. With the successful demonstration of reaching the second threshold condition by increasing the Nd:YVO₄ temperature, an application of the intracavity stimulated Raman scattering is further explored to show the benefit of this method.