摘要
本文对飞秒涡旋光束经倾斜的聚焦透镜在熔融石英中的成丝分布及其控制进行了研究,通过调节透镜倾斜角度和光束的拓扑荷等参量,获得了规则分布的等离子体细丝阵列。研究表明,通过增加透镜的倾斜角度,光丝分布由环形逐渐过渡到条状分布,并最终呈现阵列分布。此外,改变光束的拓扑荷,还可实现对激光阵列分布的调控。本研究揭示了飞秒涡旋光束在倾斜聚集条件下的成丝分布演化规律,在激光微纳加工等技术领域具有重要参考价值。
Objective The uncertainty in the number and position of laser filaments,caused by random noise and competition between filamentation and surrounding energy,severely limits their practical applications.Generating filaments with a regular distribution and a controllable number is therefore crucial for both fundamental research and technological advancements.Recent studies on femtosecond vortex beams have focused primarily on filamentation using conventional focusing lenses.However,tilting the lens can significantly influence filamentation behavior.Previous research has shown that adjusting the lens’s tilt angle allows precise control over the number,distribution,and spatial stability of femtosecond Gaussian laser filaments,effectively managing and suppressing multiple filaments.Moreover,tilted lenses are commonly used to determine a vortex beam’s topological charge,as the beam evolves into a stripe-shaped pattern characterized by alternating bright and dark fringes,with the topological charge calculated as the number of bright spots minus one.In this paper,we explore the filamentation and control of femtosecond vortex beams in fused silica using a tilted lens.Methods Initially,vortex beams with varying topological charges are focused on fused silica using a stationary lens to generate filaments.An imaging lens is used to capture the filament distribution at different propagation distances in fused silica,recorded by a digital camera.The vortex waveplate is replaced to incrementally increase the topological charge of the incident laser beam from 4 to 6 and 8,with corresponding increases in laser power due to higher self-focusing critical power.Linear propagation in air is then studied by removing the fused silica and varying the tilt angles of the focusing lens to examine the intensity distributions at different propagation distances.Subsequently,filamentation is analyzed for vortex beams in fused silica under tilted lens conditions.Finally,vortex beams with different topological charges are focused into fused silica through a tilted lens at a fixed tilt angle of 20°to evaluate the effect of topological charge on filamentation.Results and Discussions Without tilting the lens,vortex beams with varying topological charges form regular ringshaped filament arrays in fused silica.As the topological charge increases,the filament count and ring radius also increase.Along the propagation direction,re-focusing occurs,with multiple millimeter-scale filaments forming periodically within a centimeter-scale envelope.By incrementally increasing the tilt angle of the lens from 0°in steps of 3°,and selecting typical angles of 17°,20°,and 23°,the laser beam distribution evolves significantly.At 17°,the filaments exhibit an elliptical ringshaped pattern with uneven intensity.As propagation continues,the distribution transitions to an elliptical form,with enhanced intensity at the long-axis ends,resulting in stripe-like patterns.At larger tilt angles,these evolve into rectangular filament distributions.Under filamentation conditions,regular filament arrays form at the positions corresponding to intensity fringes observed during linear propagation.This method resembles interference fringe generation to create filament arrays,offering a novel approach for filamentation control.Moreover,the filament fringe count increases with the beam’s topological charge,indicating that filament formation depends not only on incident energy but also on the number of bright intensity fringes in the focused beam.Conclusions In this paper,we explore the filamentation distribution and evolution of femtosecond vortex beams in fused silica using a tilted focusing lens.A stable and controllable filament array is achieved,with its distribution tailored by adjusting the tilt angle of the lens.By modifying the lens’s tilt angle,the filament distribution transforms from a circular pattern to an array structure.Moreover,the filament distribution and number can be precisely controlled by altering the vortex beam’s topological charge and the incident laser energy.The proposed method not only introduces a novel approach for controlling laser filaments but also holds significant potential for applications in research and technical fields such as laser micro-and nano-processing.
作者
刘发倩
李东伟
张中正
张兰芝
郝作强
Liu Faqian;Li Dongwei;Zhang Zhongzheng;Zhang Lanzhi;Hao Zuoqiang(School of Physics and Electronics,Shandong Normal University,Jinan 250358,Shandong,China)
出处
《光学学报》
北大核心
2025年第2期307-313,共7页
Acta Optica Sinica
基金
国家自然科学基金(12074228,12474310,12204282)。
关键词
飞秒激光成丝
倾斜透镜
涡旋光束
拓扑荷
femtosecond laser filamentation
tilted lens
vortex beam
topological charge
