Purity and composite petal-like mode laser emission with tunable topological charge from 1 to 35

In this work, we demonstrate the generation of low-order petal mode beams with tunable topological charge from a laser system utilizing an axicon based annular pump shaping system. By tuning the shape of the pump beam and axially displacing the laser gain crystal, it was possible to generate petal-like vortex beams with variable topological charge ranging from 1 to 35 and with a maximum power of ∼ 3 W. Excellent mode purity is maintained at low pump powers, while at higher pump powers, composite modes comprising the superposition of multiple vortex modes are produced. The experimental work presented was supported by theoretical modelling from which the spatial intensity profiles of composite modes are generated. In the case of petal-like mode emission with a topological charge of 35, a maximum output power of 2.65 W was obtained with a conversion efficiency of 31.2%. Our results demonstrate the versatility of axicon-lens pump-shaping systems for the generation of a wide variety of vortex beam types with unique mode structures. We anticipate that such unique laser modes may enable what we believe to be new methodologies and techniques in cutting-edge applications spanning laser micro- and nano-machining to free-space communications.