| The vortex beams with orbital angular momentum(OAM)have been widely used in microscopic imaging,optical tweezers technology,optical communications and so on.The Laguerre-Gaussian modes,especially LG0,l modes,are the most common vortex beams,which have been studied extensively recently.Howere,many applications of LG0,l vortex beams are limited because of the only one hole structure.Therefore,compared with vortex lasers with one singularity,multi-vortex lasers,especially adjustable multi-vortex array lasers,can provide more flexibility in optical communications and optical tweezers technology.At present,the methods that can be used to obtain multi-vortex lasers include passive methods and active methods.The passive method refers to a method of using a special optical device,such as a spatial light modulator or a spiral phase plate,to convert the fundamental mode beam laser into a vortex beam outside the laser cavity.The vortex lasers generated with the passive method usually have low energy conversion efficiency and poor beam quality,and the insertion of optical components also affects the portability,flexibility and reliability of the laser.The active method is to design a special laser structure to directly generate vortex laser in the laser cavity.The vortex laser generated with the active method has good beam quality and high optical efficiency.On this basis,the vortex-array laser with high peak power obtained in the passive Q-switched microchip laser will further expand its application.Recently,orientation and separation controllable dual-vortex passively Q-switched microchip laser have been demonstrated by adjusting the offset of the collimating lens.However,this method can only obtain a dual-vortex laser with two singularitie,which will limit its application.To solve the above problems,in this paper,singularity controllable one-dimension vortex-arrays have been generated in a tilted annular beam pumped Nd:YAG/Cr4+:YAG passively Q-switched microchip laser.In the experiment,an annular pump beam shaped with a hollow focus lens was used as the pump source,the Nd:YAG/Cr4+:YAG passively Q-switched microchip laser cavity was tilted,then the double-vortex laser with two singularities were obtained at high pump power.The maximum average output power is 853 mW at the incident pump power of 5.66 W,the maximum peak power is 6.16 kW,and the optical efficiency reaches 15.1%.One-dimensional vortex-array lasers with controllable singularities have been obtained in the annular beam tilt pumped Nd:YAG/Cr4+:YAG passive Q-switched microchip laser by accurately adjusting the relative position of the collimating lens and the optical axis of pump beam.Therefore,single-vortex,one dimensional vortex-arrays with singularities tunable from two to four have been obtained depending on the applied pump power.When the incident pump power is 5.66 W,the average output power of the one-dimensional four-vortex array laser is 759 mW.The corresponding optical conversion efficiency,pulse width and peak power are 13.4%,3.5 ns,and 5.56 kW,respectively.Compared with the reported controllable dual-vortex passive Q-switched microchip laser,the number of vortexes or singularities has been doubled while the performance of the annular beam tilt pumped Nd:YAG/Cr4+:YAG passively Q-switched microchip is basically not affected.The one-dimensional vortex-arrays with tunable singularities enhance potential applications of vortex-array lasers.Nanosecond,high peak power one-dimensional vortex-arrays with tunable singularities generated in the annular beam pumped Nd:YAG/Cr4+:YAG passively Q-switched microchip laser provide theoretical and experimental guidance for the study of high-energy,multi-vortex controllable lasers. |
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