Gotovski Pavel, Šlevas Paulius, Orlov Sergej, Ulčinas Orestas, Urbas Antanas
Opt Express. 2021 Oct 11;29(21):33331-33345. doi: 10.1364/OE.438709.
Beams exhibiting long focal lines and small focal spot sizes are desired in a variety of applications and are called optical needles, with Bessel beams being a common example. Conical prisms are regularly used to generate Bessel beams, however, this method is usually plagued by an appearance of on-axis oscillations. In this work, we consider an optical element based on the space-domain Pancharatnam-Berry phase (PBP) to generate a high-power optical needle with a smooth and constant on-axis intensity profile. The phase in PBP elements is not introduced through optical path differences but results from the geometric phase that accompanies space-variant polarization manipulation. Our implementation is based on a type 2 modification of bulk transparent glass material, resulting in the formation of nanogratings with slow axes aligned perpendicular to the grating corrugation. We investigate both numerically and experimentally the stability of an optical needle generation under imperfect conditions. Influences of misalignments in the optical schema are investigated numerically and experimentally.
在各种应用中，需要具有长焦线和小焦斑尺寸的光束，这种光束被称为光学针，贝塞尔光束就是一个常见的例子。锥形棱镜经常用于产生贝塞尔光束，然而，这种方法通常会受到轴上振荡的影响。在这项工作中，我们考虑一种基于空间域潘查拉特纳姆-贝里相位（PBP）的光学元件，以产生具有平滑且恒定轴上强度分布的高功率光学针。PBP元件中的相位不是通过光程差引入的，而是由伴随空间变化偏振操纵的几何相位产生的。我们的实现基于块状透明玻璃材料的2型改性，导致形成慢轴垂直于光栅波纹排列的纳米光栅。我们通过数值模拟和实验研究了在不完美条件下光学针产生的稳定性。通过数值模拟和实验研究了光学系统中对准误差的影响。
