A V-Folded Digital Laser for On-Demand Vortex Beams by Astigmatic Transformation of Hermite–Gaussian Modes

A V-folded digital laser using a spatial light modulator (SLM) for intra-cavity loss shaping is exploited to generate Hermite–Gaussian modes with on-demand mode order. With a \pi/2 astigmatic mode converter, vortex beams carrying on-demand orbital angular momentum (OAM) with a tunable range from -11\hbar to 12\hbar are obtained. The mode order of the HG mode, hence the OAM of the vortex beam, is digitally switched by changing the phase pattern imposed on the SLM without requiring any mechanic alignment of the cavity. This work has great potential applications in various OAM-tunable vortex beams.