All-fiber generation of arbitrary cylindrical vector
beams on the first-order Poincaré sphere
LIPENG FENG,
1
YAN LI,
1,
*SIHAN WU,
1
XUN GUAN,
2
CHEN YANG,
3
WEIJUN TONG,
3
WEI LI,
1
JIFANG QIU,
1
XIAOBIN HONG,
1
YONG ZUO,
1
HONGXIANG GUO,
1
ERHU CHEN,
4
AND JIAN WU
1
1
State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications,
Beijing 100876, China
2
Center for Optics, Photonics, and Lasers, Universite Laval, Quebec, QC G1V 0A6, Canada
3
State Key Laboratory of Optical Fibre and Cable Manufacture Technology, Yangtze Optical Fibre and Cable Joint Stock Limited Company,
Wuhan 430074, China
4
Beijing Institute of Tracking and Telecommunications Technology, Beijing 100094, China
*Corresponding author: liyan1980@bupt.edu.cn
Received 4 December 2019; revised 25 April 2020; accepted 3 May 2020; posted 4 June 2020 (Doc. ID 385007); published 10 July 2020
We propose a linear mapping relationship between the polarization of the fundamental mode and the cylindrical
vector (CV) modes on the first-order Poincaré sphere (FOPS) in fiber. The new method is based on the four-
dimensional complex Jones matrices in terms of the linearly polarized mode bases. With our theoretical model, an
all-fiber approach to generate arbitrary CV beams on the FOPS is proposed theoretically and verified experimen-
tally. In the experiment, through the combination of a mode converter and a two-segment cascaded few-mode
fiber with fixed stresses, it is possible to generate all CV modes on the FOPS by only adjusting the polarization of
the fundamental mode. The Stokes parameters of the output light are measured to verify our scheme, which shows
good agreement with the theoretical prediction. The method may provide a convenient way to generate CV beams
and evolve the polarization states in any path on the FOPS, which is expected to have potential applications in
encoding information and quantum computation.
© 2020 Chinese Laser Press
https://doi.org/10.1364/PRJ.385007
1. INTRODUCTION
Polarization, originated from the vectorial nature of electromag-
netic field, is exploited in many photonic applications. In the
past, the homogeneous polarization representation by Poincaré
sphere (PS), such as linear, elliptical, and circular polarizations
[1], has drawn great attention. Recently, a light beam with a
spatially inhomogeneous state of polarization (SOP), which is
referred to as a vector beam, has been investigated because of its
unique properties [2,3]. Unlike the conventional homogeneous
SOPs, the SOP of a vector beam depends on its transverse profile.
Among vector beams, cylindrical vector (CV) beams have re-
ceived much attention due to their cylindrical symmetry in both
polarization and phase, which can be represented by a higher-
order Poincaré sphere (HOPS) [4]. The modes on the poles and
the equator have especially attracted considerable attention in
multiple applications, including optical tweezers [5,6], quantum
information processing [7], nanoscale microscopy [8–11], and
large-capacity optical communication [12]. The modes along the
longitude, which carry tunable average orbital angular momen-
tum (OAM), introduce an extra dimension to control optical
systems and thus spur novel applications from atomic manipu-
lation [13,14] to quantum information processing [15].
Driven by their various applications, the generation of CV
beams has also emerged as a hot topic. In the free-space system,
the optical elements with spatially varying phase distribution,
including spatial light modulators (SLMs), q-plates, and meta-
surfaces, are proposed to generate the modes on the first-order
PS (FOPS). Benefitting from its programmability and polari-
zation property, an SLM can be used to generate the desired
light field, either in combination with quarter-waveplates
(QWPs) or by interfering two SLM-generated coaxial Laguerre
Gaussian modes [16–20]. Besides, the modes on FOPS can also
be generated by controlling the input polarization of the q-plate
and metasurface, which can convert the orthogonal circular
polarizations to OAM modes owning opposite topological
charges with orthogonal circular polarizations [21–26]. However,
the spatial devices are bulky and expensive. Theref ore, all-fiber
generation is preferred, especially in the scenario of medical
endoscopy and optical tweezers. Currently, the generation of
CV modes based on few-mode fiber or specially designed fiber
attracts increasing interest because these systems possess fea-
tures of excellent flexibility, robust mode confinement, and
compact structure. The all-fiber system CV mode generators
consist of two stages: a polarization controller (PC) on the
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Vol. 8, No. 8 / August 2020 / Photonics Research
Research Article
2327-9125/20/081268-10 Journal © 2020 Chinese Laser Press