Intracavity generation of quasi-continuous and Q-switched Bessel–Gaussian beams with enhanced misalignment tolerance in a side-pumped Nd:YAG laser

This study demonstrated direct intracavity generation of Bessel-Gaussian (BG) beams through incorporating an axicon lens in a side-pumped Nd:YAG laser resonator, thereby mitigating the alignment sensitivity and limited power scalability characteristic of extracavity beam-shaping approaches. A theoretical model was established to analyze transverse mode dynamics within the resonator and showed good agreement with experimental validation. The output power of 0.98 W was achieved in quasi-continuous operation. The corresponding conversion efficiency was 14.9%. Under <i>Q</i>-switched operation, an output energy of 35 mJ was obtained with a pulse width of 128 ns at a repetition rate of 10 Hz, with the corresponding conversion efficiency of 8.1%. The pulse energy fluctuation was 2.4% over 30 min operation. The intracavity-axicon architecture enhanced angular misalignment tolerance by a factor of 2.4 compared to a conventional Gaussian-mode resonator. The output transverse modes versus pump energy were also measured and analyzed. This study provided a practical framework for developing compact, high-efficiency laser sources capable of generating energy-scalable BG beams.