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tight focusing of axially symmetric polarized vortex beams

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Chinese Physics B 2014年第4期23卷 251-255页

作者：周哲海郭阳宽祝连庆 Beijing Key Laboratory for Optoelectronic Measurement Technology Beijing Information Science and Technology University Beijing Engineering Research Center of Optoelectronic Information and Instruments Beijing Information Science and Technology University

tight focusing of axially symmetric polarized vortex beams is studied numerically based on vector diffraction theory. The mathematical expressions for the focused fields are derived. Simulation results show that the focused fields and phase distributions at focus are largely influenced by both the polarization order and topological charge of the incident beams. Moreover, focal spots with flat-topped or tightly-focused patterns can be flexibly achieved by carefully choosing the polar- ization order and the topological charge, which confirms the potential of such beams in wide applications, such as optical tweezers, laser printing, lithography, and material processing.

关键词： axially symmetric polarization vortex beams tight focusing beam shaping

Optical chirality induced by spin–orbit interaction of light in a tightly focused Laguerre–Gaussian beam

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Chinese Physics B 2023年第11期32卷 419-425页

作者：朱明超付圣贵满忠胜 School of Physics and Optoelectronic Engineering Shandong University of TechnologyZibo 255000China Collaborative Innovation Center of Light Manipulations and Application Shandong Normal UniversityJinan 250358China

Optical chirality is one of the important and fundamental dynamic properties of light besides energy, momentum,and angular momentum. The quantification of electromagnetic chirality has been conceptualized only recently. Now, it is well known that for paraxial plane waves of light, the optical chirality is proportional to the ellipticity of the polarization ellipse, i.e., completely independent of the phase distribution. Here it is shown that optical vortex and state of polarization of the source paraxial field both have contributions to the optical chirality of the nonparaxial field generated by tightly focused Laguerre–Gaussian(LG) beam, which is in Stark contrast to the paraxial plane wave of light known from classical optics. The physical reason is the redistribution of local electromagnetic polarization in three dimensions associated with spin–orbit interaction.

关键词： tight focusing optical chirality spin-orbit interaction

Experimental verification on tightly focused radially polarized vortex beams

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Chinese Physics B 2013年第6期22卷 356-359页

作者：杜富荣周哲海谭峭峰杨昌喜张晓青祝连庆 Beijing Engineering Research Center of Optoelectronic Information and Instruments Beijing Information Science and Technology University State Key Laboratory of Precision Measurement Technology and Instruments Tsinghua University

The theoretical and experimental results of tightly focused radially polarized vortex beams are demonstrated. An auto-focus technology is introduced into the measurement system in order to enhance the measurement precision, and the radially polarized vortex beams are generated by a liquid-crystal polarization converter and a vortex phase plate. The focused fields of radially polarized vortex beams with different topological charges at numerical apertures （NAs） of 0.65 and 0.85 are measured respectively, and the results indicate that the total intensity distribution at focus is dependent not only on the NA of the focusing objective lens and polarization pattern of the beam but also on the topological charge l of the beam. Some unique focusing properties of radially polarized vortex beams with fractional topological charges are presented based on numerical calculations. The experimental verification paves the way for some practical applications of radially polarized vortex beams, such as in optical trapping, near-field microscopy, and material processing.

关键词： vortex beams radial polarization tight focusing

Constructing ultra-long focal fields via tightly focused Bessel beams

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Chinese Optics Letters 2023年第7期21卷 59-63页

作者：郭兆金黄铭帅刘圣李鹏魏冰妍赵建林 Key Laboratory of Light Field Manipulation and Information Acquisition Ministry of Industry and Information TechnologyShaanxi Key Laboratory of Optical Information TechnologySchool of Physical Science and TechnologyNorthwestern Polytechnical UniversityXi'an 710129China

We numerically demonstrate that the tight focusing of Bessel beams can generate focal fields with an ultra-long depth of focus(DOF).The ultra-long focal field can be controlled by appropriately regulating the order of the Bessel function and the *** optical needle and an optical dark channel with nearly 100λDOF are *** optical needle has a DOF of~104.9λand a super-diffraction-limited focal spot with the size of 0.19λ^(2).The dark channel has a full-width at halfmaximum of~0.346λand a DOF of~103.8λ.Furthermore,the oscillating focal field with an ultra-long DOF can be also generated by merely changing the order of the input Bessel *** results are expected to contribute to potential applications in optical tweezers,atom guidance and capture,and laser processing.

关键词： Bessel beam vector beam tight focusing depth of focus