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16 pages, 10783 KiB

Open AccessArticle

Multilevel Spiral Axicon for High-Order Bessel–Gauss Beams Generation

by Rebeca Tudor, George Andrei Bulzan, Mihai Kusko, Cristian Kusko, Viorel Avramescu, Dan Vasilache and Raluca Gavrila

Nanomaterials 2023, 13(3), 579; https://doi.org/10.3390/nano13030579 - 31 Jan 2023

Cited by 17 | Viewed by 3248

Abstract

This paper presents an efficient method to generate high-order Bessel–Gauss beams carrying orbital angular momentum (OAM) by using a thin and compact optical element such as a multilevel spiral axicon. This approach represents an excellent alternative for diffraction-free OAM beam generation instead of complex methods based on a doublet formed by a physical spiral phase plate and zero-order axicon, phase holograms loaded on spatial light modulators (SLMs), or the interferometric method. Here, we present the fabrication process for axicons with 16 and 32 levels, characterized by high mode conversion efficiency and good transmission for visible light (λ = 633 nm wavelength). The Bessel vortex states generated with the proposed diffractive optical elements (DOEs) can be exploited as a very useful resource for optical and quantum communication in free-space channels or in optical fibers. Full article

(This article belongs to the Special Issue Nanomaterials for Photonics: Advances and Applications)

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11 pages, 4022 KiB

Open AccessArticle

Numerical and Experimental Investigation on the Optical Manipulation from an Axicon Lensed Fiber

by Wu Zhang, Yanxiao Lin, Yusong Gao, Zekai Guo, Xiangling Li, Yuhong Hu, Pengcai Dong, Qifan Zhang, Xiaohui Fang and Meng Zhang

Micromachines 2021, 12(2), 187; https://doi.org/10.3390/mi12020187 - 12 Feb 2021

Viewed by 2654

Abstract

Here we numerically and experimentally studied the optical trapping on a microsphere from an axicon lensed fiber (ALF). The optical force from the fiber with different tapered lengths and by incident light at different wavelengths is calculated. Numerically, the microsphere can be trapped [...] Read more.

y = \pm |x| / 0.5

and

y = \pm |x|

at a short incident wavelength of 900 nm. While for the fiber with tapered outline

y = \pm |x| / 2

, the microsphere can be trapped by the light with longer wavelength of 1100 nm, 1300 nm, or 1500 nm. The optical trapping to a polystyrene microsphere is experimentally demonstrated in a microfluidic channel and the corresponding optical force is derived according to the fluid flow speed. This study can provide a guidance for future tapered fibre design for optical trapping to microspheres. Full article

(This article belongs to the Special Issue Micro-Nano Science and Engineering)

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8 pages, 2890 KiB

Open AccessArticle

Combination of an Axicon Fiber Tip and a Camera Device into a Sensitive Refractive Index Sensor

by Yi-Hsin Tai, Po-Cheng Tsai, Ya-Lun Ho, Jean-Jacques Delaunay and Pei-Kuen Wei

Sensors 2019, 19(22), 4911; https://doi.org/10.3390/s19224911 - 11 Nov 2019

Cited by 6 | Viewed by 3792

Abstract

An axicon fiber tip combined with a camera device is developed to sensitively detect refractive indexes in solutions. The transparent axicon tips were made by etching optical fibers through a wet end-etching method at room temperature. When the axicon fiber tip was immersed in various refractive index media, the angular spectrum of the emitted light from the axicon fiber tip was changed. Using a low numerical aperture lens to collect the directly transmitted light, a high intensity sensitivity was achieved when the tip cone angle was about 35 to 40 degrees. We combined the axicon fiber tip with a laser diode and a smartphone into a portable refractometer. The front camera of the smartphone was used to collect the light emitted from the axicon fiber tip. By analyzing the selected area of the captured images, the refractive index can be distinguished for various solutions. The refractive index sensitivity was up to 56,000%/RIU, and the detection limit was 1.79 × 10⁻⁵ RIU. By measuring the refractive index change via the axicon fiber tip, the concentration of different mediums can be sensitively detected. The detection limits of the measurement for sucrose solutions, saline solutions, and diluted wine were 8.86 × 10⁻³ °Bx, 0.12‰, and 0.35%, respectively. Full article

(This article belongs to the Special Issue Optical Fiber Sensors and Photonic Devices)

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10 pages, 3596 KiB

Open AccessArticle

Partially Coherent Flat-Topped Beam Generated by an Axicon

by Minghui Zhang, Xianlong Liu, Lina Guo, Lin Liu and Yangjian Cai

Appl. Sci. 2019, 9(7), 1499; https://doi.org/10.3390/app9071499 - 11 Apr 2019

Cited by 8 | Viewed by 3675

Abstract

The intensity distribution of a partially coherent beam with a nonconventional correlation function, named the multi-Gaussian Schell-model (MGSM) beam, focused by an axicon was investigated in detail. Our numerical results showed that an optical needle with a flat-topped spatial profile and long focal depth was formed and that we can modulate the focal shift and focal depth of the optical needle by varying the width of the degree of coherence (DOC) and the parameters of the correlation function. The adjustable optical needle can be applied for electron acceleration, particle trapping, fiber coupling and percussion drilling. Full article

(This article belongs to the Special Issue Recent Advances in Statistical Optics and Plasmonics)

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