Investigations towards nonplanar Ho$^{3+}$:YAG ring resonator designs

Laser sources emitting around 2 µm have gained attention for their applications in material processing, medical uses, and as pump sources for optical parametric oscillators. Due to its excellent properties, Ho$^{3+}$:YAG is widely used as a laser crystal for such laser sources. Most Ho$^{3+}$:YAG lasers are based on linear resonator designs, but ring resonators have favorable properties in terms of power scaling and mechanical robustness. This study explores Ho$^{3+}$:YAG ring resonators through theoretical considerations and experimental verification of these considerations. Experimental results from a planar four-mirror acousto-optically Q-switched ring resonator include pulses with 5.3 mJ energy, 53W average output power, and a peak power of 125 kW.