Flexible generation of vector beams based on the noncommutation of Pancharatnam–Berry phase elements

AbstractThe Berry phase picture provides important insights into the electronic properties of condensed matter systems. The intrinsic anomalous Hall (AH) effect can be understood as the consequence of non-zero Berry curvature in momentum space. Here, we fabricate TI/magnetic TI heterostructures and find that the sign of the AH effect in the magnetic TI layer can be changed from being positive to negative with increasing the thickness of the top TI layer. Our first-principles calculations show that the built-in electric fields at the TI/magnetic TI interface influence the band structure of the magnetic TI layer, and thus lead to a reconstruction of the Berry curvature in the heterostructure samples. Based on the interface-induced AH effect with a negative sign in TI/V-doped TI bilayer structures, we create an artificial “topological Hall effect”-like feature in the Hall trace of the V-doped TI/TI/Cr-doped TI sandwich heterostructures. Our study provides a new route to create the Berry curvature change in magnetic topological materials that may lead to potential technological applications.

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Steering Nonlinear Twisted Valley Photons of Monolayer WS2 by Vector Beams

Nano Letters ◽

10.1021/acs.nanolett.1c02290 ◽

2021 ◽

Author(s):

HongWei Yang ◽

Jintao Pan ◽

Shuang Zhang ◽

Wenguo Zhu ◽

Li Zhang ◽

...

Keyword(s):

Vector Beams

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All-fiber cylindrical vector beams laser based on the principle of mode superposition

Optics & Laser Technology ◽

10.1016/j.optlastec.2021.106965 ◽

2021 ◽

Vol 139 ◽

pp. 106965

Author(s):

Zhipeng Dong ◽

Yimin Zhang ◽

Hongxun Li ◽

Runxia Tao ◽

Chun Gu ◽

...

Keyword(s):

Mode Superposition ◽

Vector Beams

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A hybrid broadband metalens operating at ultraviolet frequencies

Scientific Reports ◽

10.1038/s41598-021-81956-4 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Farhan Ali ◽

Serap Aksu

Keyword(s):

Dielectric Material ◽

Berry Phase ◽

Uv Light ◽

Fdtd Method ◽

Numerical Aperture ◽

Limited Range ◽

Unit Cell ◽

Dielectric Constants ◽

Phase Method ◽

Frequency Range

AbstractThe investigation on metalenses have been rapidly developing, aiming to bring compact optical devices with superior properties to the market. Realizing miniature optics at the UV frequency range in particular has been challenging as the available transparent materials have limited range of dielectric constants. In this work we introduce a low absorption loss and low refractive index dielectric material magnesium oxide, MgO, as an ideal candidate for metalenses operating at UV frequencies. We theoretically investigate metalens designs capable of efficient focusing over a broad UV frequency range (200–400 nm). The presented metalenses are composed of sub-wavelength MgO nanoblocks, and characterized according to the geometric Pancharatnam–Berry phase method using FDTD method. The presented broadband metalenses can focus the incident UV light on tight focal spots (182 nm) with high numerical aperture ($$\hbox {NA}\approx 0.8$$ NA ≈ 0.8 ). The polarization conversion efficiency of the metalens unit cell and focusing efficiency of the total metalens are calculated to be as high as 94%, the best value reported in UV range so far. In addition, the metalens unit cell can be hybridized to enable lensing at multiple polarization states. The presented highly efficient MgO metalenses can play a vital role in the development of UV nanophotonic systems and could pave the way towards the world of miniaturization.

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Generation of terahertz vector beams using dielectric metasurfaces via spin-decoupled phase control

Nanophotonics ◽

10.1515/nanoph-2020-0112 ◽

2020 ◽

Vol 9 (10) ◽

pp. 3393-3402 ◽

Cited By ~ 3

Author(s):

Yuehong Xu ◽

Huifang Zhang ◽

Quan Li ◽

Xueqian Zhang ◽

Quan Xu ◽

...

Keyword(s):

High Performance ◽

Special Kind ◽

Phase Control ◽

High Resolution Imaging ◽

Plasmon Excitation ◽

Bessel Beams ◽

Dynamic Phase ◽

Vector Beams ◽

Resolution Imaging ◽

Spatially Variant

AbstractCylindrical vector beams (CVBs), being a special kind of beams with spatially variant states of polarizations, are promising in photonics applications, including high-resolution imaging, plasmon excitation, optical trapping, and laser machining. Recently, generating CVBs using metasurfaces has drawn enormous interest owing to their highly designable, multifunctional, and integratable features. However, related studies remain unexplored in the terahertz regime. Here, a generic method for efficiently generating terahertz CVBs carrying orbital angular momentums (OAMs) is proposed and experimentally demonstrated using transmission-type spatial-variant dielectric metasurfaces, which is realized by designing the interference between the two circularly polarized transmission components. This method is based on spin-decoupled phase control allowed by simultaneously manipulating the dynamic phase and geometric phase of each structure, endowing more degree of freedom in designing the vector beams. Two types of metasurfaces which respectively generate polarization-dependent terahertz vector vortex beams (VVBs) and vector Bessel beams (VBBs) are experimentally characterized. The proposed method opens a new window to generate versatile vector beams, providing new capabilities in developing novel, compact, and high-performance devices applicable to broad electromagnetic spectral regimes.

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