Single-longitudinal-mode Hermite–Gauss and Laguerre–Gauss structured light based on an off-axis pumped Nd:YAG laser with twisted-mode cavity

We report a single-longitudinal-mode (SLM) high-order Hermite–Gauss (HG) transverse mode laser based on a twisted-mode cavity and off-axis pumping. Tunable-order HG mode output is generated from the 1064 nm Nd:YAG laser cavity, which is further converted into an SLM Laguerre–Gauss (LG) vortex beam via astigmatic mode conversion. The laser exhibits a low threshold of a couple of hundreds of milliwatts and delivers watt-level SLM output in high-order transverse modes up to HG20,0 and HG5,5 efficiently. Benefiting from the astigmatic cavity arrangement, both the two mode indices of the HG output can be tuned independently, enabling convenient control of the two mode indices of the corresponding LG vortex beam. Our results demonstrate the feasibility of the twisted-mode cavity technique for SLM high-order mode lasers, offering a straightforward solution for applications requiring narrow-linewidth structured light fields.