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1. Rainbow Archimedean spiral emission from optical fibres

   https://doi.org/10.1038/s41598-021-92313-w  

   Mangini, F.; Ferraro, M.; Zitelli, M.; Kalashnikov, V.; Niang, A.; Mansuryan, T.; Frezza, F.; Tonello, A.; Couderc, V.; Aceves, A. B.; et al (December 2021, Scientific Reports)

   null (Ed.)

   Abstract We demonstrate a new practical approach for generating multicolour spiral-shaped beams. It makes use of a standard silica optical fibre, combined with a tilted input laser beam. The resulting breaking of the fibre axial symmetry leads to the propagation of a helical beam. The associated output far-field has a spiral shape, independently of the input laser power value. Whereas, with a high-power near-infrared femtosecond laser, a visible supercontinuum spiral emission is generated. With appropriate control of the input laser coupling conditions, the colours of the spiral spatially self-organize in a rainbow distribution. Our method is independent of the laser source wavelength and polarization. Therefore, standard optical fibres may be used for generating spiral beams in many applications, ranging from communications to optical tweezers and quantum optics. 

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2. Optical trapping and manipulation for single-particle spectroscopy and microscopy

   https://doi.org/10.1063/5.0086328  

   Chen, Zhenzhen; Cai, Zhewei; Liu, Wenbo; Yan, Zijie (August 2022, The Journal of Chemical Physics)

   Optical tweezers can control the position and orientation of individual colloidal particles in solution. Such control is often desirable but challenging for single-particle spectroscopy and microscopy, especially at the nanoscale. Functional nanoparticles that are optically trapped and manipulated in a three-dimensional (3D) space can serve as freestanding nanoprobes, which provide unique prospects for sensing and mapping the surrounding environment of the nanoparticles and studying their interactions with biological systems. In this perspective, we will first describe the optical forces underlying the optical trapping and manipulation of microscopic particles, then review the combinations and applications of different spectroscopy and microscopy techniques with optical tweezers. Finally, we will discuss the challenges of performing spectroscopy and microscopy on single nanoparticles with optical tweezers, the possible routes to address these challenges, and the new opportunities that will arise. 

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3. Beam steering at the nanosecond time scale with an atomically thin reflector

   https://doi.org/10.1038/s41467-022-29976-0  

   Andersen, Trond I.; Gelly, Ryan J.; Scuri, Giovanni; Dwyer, Bo L.; Wild, Dominik S.; Bekenstein, Rivka; Sushko, Andrey; Sung, Jiho; Zhou, You; Zibrov, Alexander A.; et al (June 2022, Nature Communications)

   Abstract Techniques to mold the flow of light on subwavelength scales enable fundamentally new optical systems and device applications. The realization of programmable, active optical systems with fast, tunable components is among the outstanding challenges in the field. Here, we experimentally demonstrate a few-pixel beam steering device based on electrostatic gate control of excitons in an atomically thin semiconductor with strong light-matter interactions. By combining the high reflectivity of a MoSe₂monolayer with a graphene split-gate geometry, we shape the wavefront phase profile to achieve continuously tunable beam deflection with a range of 10°, two-dimensional beam steering, and switching times down to 1.6 nanoseconds. Our approach opens the door for a new class of atomically thin optical systems, such as rapidly switchable beam arrays and quantum metasurfaces operating at their fundamental thickness limit. 

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4. Mode conversion of hyperbolic phonon polaritons in van der Waals terraces

   https://doi.org/10.1038/s41467-025-68030-7  

   Noh, Byung-Il; Jafari_Ghalekohneh, Sina; Chen, Mingyuan; Shen, Jialiang; Janzen, Eli; Zhou, Lang; Chen, Pengyu; Edgar, James_H; Zhao, Bo; Dai, Siyuan (December 2025, Nature Communications)

   Abstract Electromagnetic hyperbolicity has driven key functionalities in nanophotonics, including super-resolution imaging, efficient energy control, and extreme light manipulation. Central to these advances are hyperbolic polaritons—nanometer-scale light-matter waves—spanning multiple energy-momentum dispersion orders with distinct mode profiles and incrementally high optical momenta. In this work, we report the mode conversion of hyperbolic polaritons across different dispersion orders by breaking the structure symmetry in engineered step-shape van der Waals (vdW) terraces. The mode conversion from the fundamental to high-order hyperbolic polaritons is imaged using scattering-type scanning near-field optical microscopy (s-SNOM) on both hexagonal boron nitride (hBN) and alpha-phase molybdenum trioxide (α-MoO₃) vdW terraces. Our s-SNOM data, augmented with electromagnetics simulations, further demonstrate the alteration of polariton mode conversion by varying the step size of vdW terraces. The mode conversion reported here offers a practical approach toward integrating previously independent different-order hyperbolic polaritons with ultra-high momenta, paving the way for promising applications in nano-optical circuits, sensing, computation, information processing, and super-resolution imaging. 

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5. Multifunctional resonant wavefront-shaping meta-optics based on multilayer and multi-perturbation nonlocal metasurfaces

   https://doi.org/10.1038/s41377-022-00905-6  

   Malek, Stephanie C.; Overvig, Adam C.; Alù, Andrea; Yu, Nanfang (August 2022, Light: Science & Applications)

   Abstract Photonic devices rarely provide both elaborate spatial control and sharp spectral control over an incoming wavefront. In optical metasurfaces, for example, the localized modes of individual meta-units govern the wavefront shape over a broad bandwidth, while nonlocal lattice modes extended over many unit cells support high quality-factor resonances. Here, we experimentally demonstrate nonlocal dielectric metasurfaces in the near-infrared that offer both spatial and spectral control of light, realizing metalenses focusing light exclusively over a narrowband resonance while leaving off-resonant frequencies unaffected. Our devices attain this functionality by supporting a quasi-bound state in the continuum encoded with a spatially varying geometric phase. We leverage this capability to experimentally realize a versatile platform for multispectral wavefront shaping where a stack of metasurfaces, each supporting multiple independently controlled quasi-bound states in the continuum, molds the optical wavefront distinctively at multiple wavelengths and yet stay transparent over the rest of the spectrum. Such a platform is scalable to the visible for applications in augmented reality and transparent displays. 

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