Efficient and flexible generation of vortex pulses from a mode-locked all-solid-state laser by self-consistent oscillation

The potential widespread adoption of ultrafast vortex pulses has been hindered by a long-standing challenge in their direct generation with high efficiency and flexible topological charge (TC) tunability. Conventional intracavity methods for producing higher-order vortices, for instance, often suffer from inefficient mode-matching, which, in turn, leads to poor lasing efficiency, limited output power, and inferior TC tuning capability. In this paper, we present a solution to this challenge through a novel mode-locked Nd:YVO4 vortex laser based on a self-consistent intracavity mode conversion scheme, without the need to satisfy the corresponding high-order mode-matching condition. By integrating a semiconductor saturable absorber mirror for mode-locking and an intracavity vortex mode converter utilizing a Q-plate (QP), the laser can easily achieve stable emissions of vortex pulses with an arbitrary TC at a central wavelength of 1064 nm, by simply substituting the corresponding QP. In a proof-of-principle experiment, a slope efficiency of 33.1% is obtained for the LG0,1 vortex mode and maintained at 28.9% for higher-order modes up to LG0,16. The generated LG0,1 and LG0,16 vortex pulses have durations of 10.2 and 10.8 ps, with average output powers of 3.51 and 3.16 W, respectively. This work provides a robust framework for the design and construction of efficient, high-power pulsed vortex lasers with a well-defined and selectable TC, holding significant promise for applications in micro-manufacturing, optical trapping, and related fields.