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We demonstrate an ultra-compact (8 mm-long) green orbital Poincaré Pr 3+ :LiYF 4 (YLF) laser, in which the intracavity lasing modes are represented as eigenmodes on an equivalent orbital Poincaré sphere (eOPS). This is achieved through the simple application of an 'optical-needle' pumping geometry in conjunction with off-axis laser mode-manipulation. Optical vortices that are produced and mapped on north and south poles of the eOPS exhibit a maximum output power of 304 mW with a pump-to-laser-output slope efficiency of 12%. In addition, higher-order structured modes, including Ince Gaussian (IG), helical IG (HIG), Hermite-Laguerre Gaussian (HLG) and vortex lattices, can be directly generated from the laser cavity.

Here we demonstrate intracavity frequency-doubling of an ultra-compact (cavity length < 20 mm) Pr 3+ :LiYF 4 (YLF) orbital Poincaré laser, in which the fundamental modes are represented on an equivalent orbital Poincaré sphere (eOPS) and a singularities hybrid evolution nature sphere (SHENS). The generated ultraviolet (UV, 320 nm) output carries orbital angular momentum (OAM), and it typically exhibits an optical bottle beam with a 3-dimensional dark core, formed of a coherent superposition of eigen Laguerre-Gaussian (LG) modes. Such ultraviolet structured light beams with OAM offer many advanced applications from microscopy to materials processing.