Under the framework of generalized Lorenz-Mie theory, we calculate the radiation force and torque exerted on a chiral sphere by a Gaussian beam. The theory and codes for axial radiation force are verified when the chiral sphere degenerates into an isotropic sphere. We discuss the influence of a chirality parameter on the radiation force and torque. Linearly and circularly polarized incident Gaussian beams are considered, and the corresponding radiation forces and torques are compared and analyzed. The polarization of the incident beam considerably influences radiation force of a chiral sphere. In trapping a chiral sphere, therefore, the polarization of incident beams should be chosen in accordance with the chirality. Unlike polarization, variation of chirality slightly affects radiation torque, except when the imaginary part of the chirality parameter is considered.

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In this paper, a dual-band dual-polarized reflectarray for generating dual beams with respect to carrying two different orbital angular momentum (OAM) topological charges operating in the C-band in horizontal polarization and in the X-band in vertical polarization is proposed, with two separate horns performing on the two proposed bands as the feeding. The proposed reflectarray consists of two band reflective element cells operating in two orthogonal directions. Owing to the two composing elements orthogonally interleaved on the reflectarray surface, the corresponding phase compensation performance in one band can be slightly affected by the elemental resonance in another band; thus, the degree of the coupling between the elements with different-band operations can be neglected, resulting in fairly independent phase compensation. In other words, the desired OAM generation reflectarray, to some extent, can be developed based on two different frequency band OAM reflectarrays at the same aperture. In addition, simulations and measurements strongly suggest the feasibility and the validity of the approach, which provides a solid foundation for the application of multi-band reflectarrays to the multi-OAM-mode generation.

BiOX x Y 1−x (X, Y = Cl, Br, and I) solid solutions have been regarded as promising photocatalysts attributed to their unique layered structure, tunable band structure, and chemical and optical stability. In this study, BiOBr x I 1−x nanoplate solid solutions with a high exposure of {001} crystal facets were prepared by a facile alcoholysis method at room temperature and atmospheric pressure. X-ray diffraction (XRD) peaks exhibited a slight shift to lower diffraction angle with the increase of I content in BiOBr x I 1−x samples, which resulted in a gradual increase in their cell parameters. Field emission scanning electron microscopy (FESEM) and transmission electron microscope (TEM) images revealed that BiOBr x I 1−x samples exhibited 2D plate-like structure with the in-plane wrinkles. The regular changes in optical absorption threshold and E g value seen in UV-vis diffuse reflectance spectra (UV-vis DRS) indicated that the optical absorption property and band structure could be modulated by the formation of BiOBr x I 1−x solid solutions. The photocatalytic degradation of active dye Rhodamine B (RhB) over BiOBr x I 1−x solid solutions showed that BiOBr 0.75 I 0.25 had the best photocatalytic activity. The RhB photodegradation processes followed a pseudo-first-order kinetic model. The synergistic effect of structural factors (including amount of exposed {001} facets, interlayer spacing of (001) plane, and energy-level position of the valence band) determined the photocatalytic performance of BiOBr x I 1−x solid solutions.

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