Fiber-based mode converter for generating optical vortex beams

Ruishan Chen; Jinghao Wang; Xiaoqiang Zhang; Junna Yao; Hai Ming; Anting Wang

doi:10.29026/oea.2018.180003

Journals >Opto-Electronic Advances >Volume 1 >Issue 7 >Page 180003 > Article

Opto-Electronic Advances
Vol. 1, Issue 7, 180003 (2018)

Fiber-based mode converter for generating optical vortex beams

Ruishan Chen¹, Jinghao Wang¹, Xiaoqiang Zhang^1、2, Junna Yao¹, Hai Ming¹, and Anting Wang^1、*

Author Affiliations

¹Department of Optics and Optical Engineering, University of Science and Technology of China, Hefei 230026, China

²Hefei General Machinery Research Institute, Hefei 230031, China

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DOI: 10.29026/oea.2018.180003 Cite this Article

Ruishan Chen, Jinghao Wang, Xiaoqiang Zhang, Junna Yao, Hai Ming, Anting Wang. Fiber-based mode converter for generating optical vortex beams[J]. Opto-Electronic Advances, 2018, 1(7): 180003 Copy Citation Text

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Abstract

In this work, an all-fiber-based mode converter for generating orbital angular momentum (OAM) beams is proposed and numerically investigated. Its structure is constructed by cascading a mode selective coupler (MSC) and an inner elliptical cladding fiber (IECF). OAM modes refer to a combination of two orthogonal LPlm modes with a phase difference of ±π/2. By adjusting the parameters and controlling the splicing angle of MSC and IECF appropriately, higher-order OAM modes with topological charges of l = ±1, ±2, ±3 can be obtained with the injection of the fundamental mode LP01, resulting in a mode-conversion efficiency of almost 100%. This achievement may pave the way towards the realization of a compact, all-fiber, and high-efficiency device for increasing the transmission capacity and spectral efficiency in optical communication systems with OAM mode multiplexing.

Keywords

fiber optics mode-division multiplexing optical vortices singular optics

$ {P_{\rm{c}}} = \frac{{{P_0}}}{{1 + {{(\kappa \delta )}^2}}}{\sin ^2}(\sqrt {{\kappa ^2} + {\delta ^2}} \cdot L), $

(1)

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$ \begin{array}{l} \kappa = {( - 1)^l}\frac{{2\sqrt 2 k{\rho _2}{\Delta _2}{u_1}{u_2}{n_{{\rm{co}}}}}}{{{\rho _1}{v_1}v_2^3}}\\ \times \frac{{{K_l}({\omega _1}d/{\rho _1})}}{{{K_1}({\omega _1})\sqrt {{K_{l - 1}}({\omega _2}){K_{l + 1}}({\omega _2})} }}{\rm{cos}}(l\alpha ) \end{array} $

(2)

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$ OA{M_{ \pm l1}} = LP_{l1}^\theta \pm {\rm{i}} \times LP_{l1}^{ - \theta }{\rm{ = }}{F_{l1}}(r)\exp ( \pm {\rm{i}}l\varphi ). $

(3)

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$ \begin{array}{l} LP_{l1}^\theta + LP_{l1}^{ - \theta } = {F_{l1}}(r)/\sqrt 2 \cos (l\varphi )\;\;\;{\rm{or}}\\ LP_{l1}^\theta - LP_{l1}^{ - \theta } = {F_{l1}}(r)/\sqrt 2 \sin (l\varphi ), \end{array} $

(4)

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$ \Delta {n_{{\rm{eff}}}} = {n_{{\rm{eff}}}}(LP_{l1}^{ - \theta }) - {n_{{\rm{eff}}}}(LP_{l1}^\theta ). $

(5)

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$ {\kern 1pt} LP_{l1}^\theta + {\rm{exp(i}}\omega {\rm{)}} \cdot LP_{l1}^{ - \theta }{\rm{ = }}{A_{l1}}(r, p, \varphi )\exp [{\rm{i}}\alpha (p, \varphi )], $

(6)

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$ \begin{array}{l} {\kern 1pt} {A_{l1}}(r, p, \varphi ) = {F_{l1}}(r)\sqrt {1 + 2\cos (l\varphi )\sin (l\varphi )\cos p}, \\ {\kern 1pt} \alpha (p, \varphi ) = \arctan [\frac{{\sin p\sin (l\varphi )}}{{\cos (l\varphi ) + \cos p\sin (l\varphi )}}], \end{array} $

(7)

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$ \frac{{\partial \alpha (p, \varphi )}}{{\partial \varphi }}{\rm{ = }}\frac{{\sin p}}{{1 + \sin (2l\varphi )\cos p}}. $

(8)

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Ruishan Chen, Jinghao Wang, Xiaoqiang Zhang, Junna Yao, Hai Ming, Anting Wang. Fiber-based mode converter for generating optical vortex beams[J]. Opto-Electronic Advances, 2018, 1(7): 180003

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