The degenerating diffraction far-field propagation properties of the conical double half-Gaussian hollow beams

The far-field propagation properties of conical double half-Gaussian hollow beams in the condition of Collins formula are studied. Because of the cone angle of this kind of hollow beams, the diffraction is compensated and the inner diameter is turning bigger by the rule of geometric optics as the propagation distance is increasing, whereas the degenerating diffraction phenomenon is turned out. The far-field intensity distribution of the conical double half-Gaussian hollow beams in the condition of in-Collins formula is researched, and the results show that the far-field propagation properties can be depicted by this model. In the experiment, this kind of hollow beams are obtained by means of the dual-reflecting splitting optical system, and the inner diameter of the hollow beams is tested. The results show good agreement with the propagation theory in the condition of in-Collins formula.

The research of propagation characteristic and formation of double half-Gaussian hollow beams

A new kind of hollow beams, double half-Gaussian hollow beams,was put forward. With the help of the Collins formula, the analytical equation of propagation and transformation of the hollow laser beams in free space was deduced. The simulation shows that the intensity exhibits the three-dimensional trap distribution in the near-field, while the double half-Gaussian hollow beams turn into solid laser beams when propagating a certain distance, which shows the characteristics of self-focus. The double half-Gaussian hollow beams were obtained by means of the dual-reflecting splitting optical system. The intensity of the vertical loop in different distances was tested, which shows that the analytical equation of propagation and transformation is in agreement with the result.

产生波长793nm中空光束的双包层光纤的优化设计

随着大功率掺铥光纤激光器(TDFL)的广泛应用及其相关技术的迅速发展,多芯TDFL受到了广大研究者的广泛关注,其中有效的包层泵浦技术是实现多芯TDFL高功率输出的决定因素。TDFL通常采用波长为793 nm的激光进行泵浦,通过不断优化工作在793 nm波长的双包层光纤的结构,对其中传输的高斯光束进行整形,当纤芯尺寸为6μm,环尺寸为6.5μm且内包层折射率为1.462 4时,最终获得了合适暗斑尺寸和环状光束宽度的中空光束。利用所设计的双包层光纤泵浦多芯TDFL,可使多芯光纤内掺杂的铥离子更好的吸收泵浦光,提高工作于2μm波段多芯TDFL的输出激光功率和泵浦效率。

中空双螺旋微机器人的飞秒激光动态全息高效加工

为了实现微机器人的快速批量制造,提出一种飞秒贝塞尔光束叠加干涉方法生成带侧瓣的环形光场,并结合动态全息加工术实现了中空螺旋微机器人的高效制造。对根据贝塞尔传输函数生成的贝塞尔全息图进行叠加,并对产生的光场进行仿真和实验测量。利用叠加的全息图加工得到具有不同侧瓣数目(2~4)的环形结构,分析了两种不同参数对侧瓣宽度和圆环直径的影响。通过引入动态全息加工方法,实现了中空双螺旋微机器人的高效快速加工,微机器人宽为25μm、长度为100μm。最后,利用旋转磁场驱动微机器人在微流体环境实现运动。实验表明,加工单个微机器人仅需6 s,旋转磁场下微机器人在7 s内沿直线前进400μm。该动态全息方法能够快速制备出中空双螺旋微机器人并实现无线磁驱动,为批量制造具有运载能力的磁驱微机器人提供了一种新的途径。

实现双半高斯空心光束宽度半径比调谐范围为0.1~1的技术研究

提出了一种利用改进型的卡塞格林光学系统（反射式正圆锥镜和球面反射镜相结合的光学系统）来产生一种光强分布特殊的空心激光束（双半高斯空心激光束）的新方案。详细分析了正圆锥镜的锥角、高斯光束的张角、球面反射镜的曲率半径等因素对该光学系统的球差以及宽度半径比的影响。通过对上述参数的调整,可以很容易获得宽度半径比的可控范围为0.1~1的双半高斯空心激光束。测试结果验证了由该系统所产生的空心光束确属于双半高斯空心光束范畴。