Tight focusing of linearly and circularly polarized vortex beams; effect of third-order spherical aberration

A small electron probe has many applications in many fields and in the case of the STEM, the probe size essentially determines the ultimate resolution. However, there are many difficulties in obtaining a very small probe.Spherical aberration is one of them and all existing probe forming systems have non-zero spherical aberration. The ultimate probe radius is given byδ = 0.43Csl/4ƛ3/4where ƛ is the electron wave length and it is apparent that δ decreases only slowly with decreasing Cs. Scherzer pointed out that the third order aberration coefficient always has the same sign regardless of the field distribution, provided only that the fields have cylindrical symmetry, are independent of time and no space charge is present. To overcome this problem, he proposed a corrector consisting of octupoles and quadrupoles.

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The generation of a complete spiral spot and multi split rings by focusing three circularly polarized vortex beams

Optics Communications ◽

10.1016/j.optcom.2013.12.058 ◽

2014 ◽

Vol 318 ◽

pp. 100-104 ◽

Cited By ~ 6

Author(s):

Jiannong Chen ◽

Xiumin Gao ◽

Linwei Zhu ◽

Qinfeng Xu ◽

Wangzi Ma

Keyword(s):

Circularly Polarized ◽

Vortex Beams

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Aberrations

Modern Optics Simplified ◽

10.1093/oso/9780198842859.003.0007 ◽

2019 ◽

pp. 215-248

Author(s):

B. D. Guenther

Keyword(s):

Hubble Space Telescope ◽

Spherical Aberration ◽

Chromatic Aberration ◽

Optical Path Difference ◽

Path Difference ◽

Optical Path ◽

Wavefront Aberration ◽

Third Order ◽

The Third ◽

Field Curvature

Using simple ray tracinig technliques presented in Chapter 6, we demonstrate that a general ray is not focused to the position predicted by paraxial theory. The aberration displayed is spherical aberration. Two methods of measuring aberration: the use of optical path difference to characterize wavefront aberration. The transverse ray coefficients to generate a ray intercept plot. Experimental examples of all the third order aberrations are given. In addition to spherical aberration, they include coma, astigmatism, field curvature, and distortion Only two types of aberration correction are discussed, removal of spherical aberration in the Hubble Space telescope and chromatic aberration. A detailed example of chromatic aberration is given.

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Tight focusing of J0-correlated azimuthally polarized vortex beams

High Power Laser and Particle Beams ◽

10.3788/hplpb20132508.1945 ◽

2013 ◽

Vol 25 (8) ◽

pp. 1945-1950

Author(s):

饶连周 Rao Lianzhou ◽

林惠川 Lin Huichuan ◽

许国忠 Xu Guozhong

Keyword(s):

Tight Focusing ◽

Vortex Beams

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Strongly Focused Circularly Polarized Optical Vortices Regulated by a Fractal Conical Lens

Applied Sciences ◽

10.3390/app10010028 ◽

2019 ◽

Vol 10 (1) ◽

pp. 28

Author(s):

Zhirong Liu ◽

Kelin Huang ◽

Anlian Yang ◽

Xun Wang ◽

Philip H. Jones

Keyword(s):

Angular Momentum ◽

Optical Tweezers ◽

Numerical Aperture ◽

Optical Element ◽

Optical Vortex ◽

Optical Vortices ◽

Circularly Polarized ◽

Strong Focusing ◽

New Type ◽

Vortex Beams

In this paper, a recently-proposed pure-phase optical element, the fractal conical lens (FCL), is introduced for the regulation of strongly-focused circularly-polarized optical vortices in a high numerical aperture (NA) optical system. Strong focusing characteristics of circularly polarized optical vortices through a high NA system in cases with and without a FCL are investigated comparatively. Moreover, the conversion between spin angular momentum (SAM) and orbital angular momentum (OAM) of the focused optical vortex in the focal vicinity is also analyzed. Results revealed that a FCL of different stage S could significantly regulate the distributions of tight focusing intensity and angular momentum of the circularly polarized optical vortex. The interesting results obtained here may be advantageous when using a FCL to shape vortex beams or utilizing circularly polarized vortex beams to exploit new-type optical tweezers.

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