Nonlinear generation of Airy vortex beam

Author(s):
Hui Li and Haigang Liu and Xianfeng Chen

Abstract:

“Recently, hybrid beams have sparked considerable interest because of their properties coming from different kinds of beams at the same time. Here, we experimentally demonstrate Airy vortex beam generation in the nonlinear frequency conversion process when the fundamental wave with its phase modulated by a spatial light modulator is incident into a homogeneous nonlinear medium. In our experiments, second harmonic Airy circle vortex beams and Airy ellipse vortex beams were generated and the topological charge was also measured. The parabolic trajectory of those Airy vortex beams can be easily adjusted by altering the fundamental wave phase. This study provides a simple way to generate second harmonic Airy vortex beams, which may broaden its future use in optical manipulation and light-sheet microscopy.”

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Publication: Optics Express
Issue/Year: Optics Express Volume 26, Issue 16
DOI: 10.1364/oe.26.021204

On-Chip Detection of Orbital Angular Momentum Beam by Plasmonic Nanogratings

Author(s):

Ji Chen and Xi Chen and Tao Li and Shining Zhu

Abstract:

“Thanks to the unlimited orthogonal states, the orbital angular momentum (OAM) light is widely accepted as a promising carrier for high information multiplexing in optical communications, in which the OAM detection is an important issue. To keep up with the ever‐growing demand for compact integration, here, a plasmonic grating is employed to spatially couple the OAM modes into two separated propagating surface plasmon polariton (SPP) beams with different splitting angles. These splitting angles are found to strongly rely on the topological charges of the incident beams and are insensitive to the specific location of the OAM beam illumination, which provides an intuitive detection of the OAM modes without particular alignment. Besides, a further unidirectional SPP launching from the OAM beam is also achieved by a particular composite grating. With such composite grating, both the topological charge value and sign of OAM beam in a single measurement can be detected. Our results provide a convenient method for alignment‐free OAM detection by a compact device, and would inspire more multiplexing applications in nanophotonics.”

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Publication: Laser & Photonics Reviews
Issue/Year: Laser & Photonics Reviews Volume 12, Issue 8 (2018)
DOI: 10.1002/lpor.201700331

Experimental demonstration of tunable refractometer based on orbital angular momentum of longitudinally structured light

Author(s):

Dorrah, Ahmed H and Zamboni-Rached, Michel and Mojahedi, Mo

Abstract:

“The index of refraction plays a decisive role in the design and classification of optical materials and devices; therefore, its proper and accurate determination is essential. In most refractive index (RI) sensing schemes, however, there is a trade-off between providing high-resolution measurements and covering a wide range of RIs. We propose and experimentally demonstrate a novel mechanism for sensing the index of refraction of a medium by utilizing the orbital angular momentum (OAM) of structured light. Using a superposition of co-propagating monochromatic higher order Bessel beams with equally spaced longitudinal wavenumbers, in a comb-like setting, we generate nondiffracting rotating light structures in which the orientation of the beam’s intensity profile is sensitive to the RI of the medium (here, a fluid). In principle, the sensitivity of this scheme can exceed ∼ 2700°/RIU with a resolution of ∼ 10-5 RI unit (RIU). Furthermore, we show how the unbounded degrees of freedom associated with OAM can be deployed to offer a wide dynamic range by generating structured light that evolves into different patterns based on the change in RI. The rotating light structures are generated by a programmable spatial light modulator (SLM). This provides dynamic control over the sensitivity, which can be tuned to perform coarse or fine measurements of the RI in real time. This, in turn, allows high sensitivity and resolution to be achieved simultaneously over a very wide dynamic range, which is a typical trade-off in all RI sensing schemes. We thus envision that this method will open new directions in refractometry and remote sensing.”

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Publication: Light: Science \& Applications
Issue/Year: Light: Science & Applications accepted article preview 18 May 2018
DOI: 10.1038/s41377-018-0034-9

Spin-orbit interaction of light induced by transverse spin angular momentum engineering

Author(s):

Zengkai Shao and Jiangbo Zhu and Yujie Chen and Yanfeng Zhang and Siyuan Yu

Abstract:

“The investigations on optical angular momenta and their interactions have broadened our knowledge of light’s behavior at sub-wavelength scales. Recent studies further unveil the extraordinary characteristics of transverse spin angular momentum in confined light fields and orbital angular momentum in optical vortices. Here we demonstrate a direct interaction between these two intrinsic quantities of light. By engineering the transverse spin in the evanescent wave of a whispering-gallery-mode-based optical vortex emitter, a spin-orbit interaction is observed in generated vortex beams. Inversely, this unconventional spin-orbit interplay further gives rise to an enhanced spin-direction locking effect in which waveguide modes are unidirectionally excited, with the directionality jointly controlled by the spin and orbital angular momenta states of light. The identification of this previously unknown pathway between the polarization and spatial degrees of freedom of light enriches the spin-orbit interaction phenomena, and can enable various functionalities in applications such as communications and quantum information processing.”

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Publication: Nature Communications
Issue/Year: Nature Communicationsvolume 9, Article number: 926 (2018)
DOI: 10.1038/s41467-018-03237-5

Controllable mode transformation in perfect optical vortices

Author(s):

Xinzhong Li and Haixiang Ma and Chuanlei Yin and Jie Tang and Hehe Li and Miaomiao Tang and Jingge Wang and Yuping Tai and Xiufang Li and Yishan Wang

Abstract:

“We report a novel method to freely transform the modes of a perfect optical vortex (POV). By adjusting the scaling factor of the Bessel–Gauss beam at the object plane, the POV mode transformation can be easily controlled from circle to ellipse with a high mode purity. Combined with the modulation of the cone angle of an axicon, the ellipse mode can be freely adjusted along the two orthogonal directions. The properties of the “perfect vortex” are experimentally verified. Moreover, fractional elliptic POVs with versatile modes are presented, where the number and position of the gaps are controllable. These findings are significant for applications that require the complex structured optical field of the POV.”

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Publication: Opt. Express
Issue/Year: Opt. Express, Vol. 26, Issue 2, pp. 651-662 (2018)
DOI: 10.1364/OE.26.000651

Tailoring arbitrary hybrid Poincaré beams through a single hologram

Author(s):

Shiyao Fu and Yanwang Zhai and Tonglu Wang and Ci Yin and Chunqing Gao

Abstract:

“Hybrid Poincaré beams (HPBs) are a kind of structure field with anisotropic polarizations. Here, we demonstrate an approach to tailor HPBs with arbitrary states, through encoding a single hologram on a liquid-crystal display device along with a stable optical system. The state of the obtained HPB is determined only by the encoded holograms with special design, which means it is not necessary to adjust any optical elements or hardware when generating various HPB states. Moreover, perfect HPBs can also be generated through the proposed scheme. In the experiment, the obtained HPBs are analyzed through a polarizer and a special parameter S3/S0, showing good agreement with prediction. This work opens an insight in encoding single holograms for tailoring arbitrary HPBs and inspires various applications.”

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Publication: Applied Physics Letters
Issue/Year: Applied Physics Letters Volume 111, Issue 21
DOI: 10.1063/1.5008954

Non-diffractive Bessel-Gauss beams for the detection of rotating object free of obstructions

Author(s):

Shiyao Fu and Tonglu Wang and Zheyuan Zhang and Yanwang Zhai and Chunqing Gao

Abstract:

“Bessel-Gauss beams carrying orbital angular momentum are widely known for their non-diffractive or self-reconstructing performance, and have been applied in lots of domains. Here we demonstrate that, by illuminating a rotating object with high-order Bessel-Gauss beams, a frequency shift proportional to the rotating speed and the topological charge is observed. Moreover, the frequency shift is still present once an obstacle exists in the path, in spite of the decreasing of received signals. Our work indicates the feasibility of detecting rotating objects free of obstructions, and has potential as obstruction-immune rotation sensors in engine monitoring, aerological sounding, and so on.”

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Publication: Optics Express
Issue/Year: Optics Express , Vol. 25, Issue 17, pp. 20098- 20108 (2018)
DOI: 10.1364/OE.25.020098

Free-space optical communication link using perfect vortex beams carrying orbital angular momentum ({OAM})

Author(s):

Fuquan Zhu and Sujuan Huang and Wei Shao and Jie Zhang and Musheng Chen and Weibing Zhang and Junzhang Zeng

Abstract:

“We experimentally demonstrate a free-space optical communication link using perfect vortex beams. Perfect vortex beams with different topological charges are generated using a phase-modulation-type spatial light modulator (SLM) loaded with novel phase holograms based on the Bessel function. With the help of a microscope objective and simple lens, perfect vortex beams are transmitted effectively for a certain distance. After completing the demodulation of perfect vortex beams carrying OFDM 16-QAM signals and a series of offline processing on the Gaussian bright spot demodulated from the perfect vortex beams, we also achieve a communication link. The constellations and mean bit error rates (BER) of subcarriers are shown.”

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Publication: Optics Communications
Issue/Year: Optics Communications Volume 396, Pages 50-57
DOI: 10.1016/j.optcom.2017.03.023

Robust laser beam engineering using polarization and angular momentum diversity

Author(s):

Priyanka Lochab and P. Senthilkumaran and Kedar Khare

Abstract:

“We describe a laser beam engineered to carry l = 0 and l = 1 orbital angular momentum (OAM) states in orthogonal polarizations. It is observed that on collinear transmission through a random phase screen, the far field diffraction intensity patterns for the individual polarization states are complementary with significant negative correlation. As a result the combined intensity profile for the beam remains robust against time varying phase fluctuations. In our simulation and experiment the SNR for the central lobe of the combined far-field diffraction pattern defined as mean divided by the standard deviation of intensity values shows significant improvement over that for individual polarizations. The concept of polarization and OAM diversity as demonstrated here can be considered valuable for robust laser beam engineering without the requirement of any active real-time correction methods.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 25 , Issue 15 , pp. 17524-17524 (2018)
DOI: 10.1364/OE.25.017524

Selective acquisition of multiple states on hybrid Poincare sphere

Author(s):

Shiyao Fu and Tonglu Wang and Zheyuan Zhang and Yanwang Zhai and Chunqing Gao

Abstract:

“We experimentally demonstrate an approach to acquire multiple beams on a hybrid Poincare sphere, where different states are present at various diffraction orders. Moreover, the state in each diffraction order is controllable. Our scheme is accomplished by employing liquid crystal spatial light modulators, which act as anisotropic polarization diffraction gratings. The multiple states generated in the experiment, with various polarization distributions, are verified by a polarizer and a tilted lens, showing good agreement with the prediction. Such a proposed scheme has potential applications in the domains as laser machining, nanoparticle manipulations, and so on.”

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Publication: Applied Physics Letters
Issue/Year: Applied Physics Letters Volume 110, Issue 19
DOI: 10.1063/1.4983284