Investigation of super-resolution in microsphere-assisted microscopy with the Poynting vector of the dipole model.

In this paper, the Fourier spectrum of an image in microsphere-assisted microscopy (MAM) and the wavenumber decomposition of the Poynting vector of the dipole model are compared for the first time to study the super-resolution performance within several wavelengths in MAM. Firstly, an experiment using microsphere-assisted microscopy is performed, and the fast Fourier transformation (FFT) spectra of the images along the distance are studied. Then the Poynting vector in the point dipole field is theoretically investigated based on the spectral decomposition of dyadic Green's function. Our study finds that the result of decomposition of the Poynting vector corresponds with the propagation results of components with different transverse wavenumbers kρ in an experiment. Even when kρ reaches 1.7k0, the waves can still arrive outside one wavelength. Our work is the first effort (to our knowledge) to associate the Fourier spectrum and the decomposition of the Poynting vector together, and it may contribute to the quantitative exploration of super-resolution performance in MAM in the future.

Thickness-modulated optical nonlinearity of colloidal CdSe-CdS core-shell nanoplatelets: large two-photon absorption and self-focusing effects.

As a one-dimensional quantum confined material, colloidal semiconductor nanoplatelets have been widely studied as potential nonlinear materials due to their strong exciton effect and large two-photon absorption cross-section similar to that of two-dimensional materials. In this work, CdSe-CdS core-shell nanoplatelets were synthesized and third-order nonlinear optical properties related to shell thickness were measured using the Z-scan method. Measurement revealed a monotonic increase in the imaginary part of the third-order nonlinear susceptibility (Imχ(3)) of CdSe-CdS nanoplatelets, ranging from 0.62 × 10-13 esu to 2.43 × 10-13 esu, with the growth of shell thickness. The real part of the third-order nonlinear susceptibility (Reχ(3)) shows a non-monotonic change between 4.28 × 10-13 esu and 1.99 × 10-13 esu. The trends were further elucidated by analyzing the optical properties of the nanoplatelets, such as absorption, photoluminescence, and quantum yield, and understanding the variations in defect distribution, exciton binding energy, and quantum confinement effects. The results indicated that the appropriate passivation of the CdS shell effectively enhanced the luminescent performance and third-order nonlinearity of the nanoplatelets, while the induced defects and weakened quantum confinement effects due to the continued shell growth resulted in the opposite effect.

Anisotropic nonlinear Kerr media: Z-scan characterization and interaction with hybridly polarized beams.

The interaction of intense laser with matter gives rise to a variety of novel nonlinear optical effects, reflects the nonlinear optical property of a material, and modulates the light propagation behavior. Herein, we investigate anisotropic Kerr nonlinearities induced by both scalar and vectorial optical fields. Firstly, we present the anisotropic third-order nonlinear refraction indexes related to left-hand and right-hand components, which depend on the ellipticity, the dichroism coefficient, the anisotropy coefficient, as well as the crystal orientation angle. Secondly, we develop the elliptically polarized light Z-scan technique for characterizing third-order nonlinear susceptibility tensor in anisotropic nonlinear Kerr media, which is demonstrated experimentally. Lastly, with the known nonlinear optical parameters, we numerically study both the vectorial self-diffraction behaviors and spin angular momentum (SAM) characteristics of hybridly polarized beams induced by an anisotropic Kerr nonlinearity. It is shown that the anisotropic Kerr nonlinearity offers a new approach to manipulate the polarization-structured light field, which has potential applications in SAM manipulation, three-dimensional crystal orientation, and polarization-sensitive detection and sensing.

Configurations and characteristics of boron and B36 clusters.

Characteristics of the ring and linear structures of the boron cluster B36 and its doped clusters were investigated with DFT/B3LYP/6-31G. The results illustrate that the ring B3 structure is the most stable configuration compared with other rings. Odd and even linear structures have different bonding; there is one different bond in the center of even linear structures, while the remaining bonds have left and right symmetry. The B36 cluster upholds the configuration rule of pure ring and linear molecules. However, the N-doped B36N cluster exhibits obvious distortion compared with the B36 molecule. The impurity N changes the structure of the energy band of the B36 cluster. The wavelength of absorption spectra and electronic circular dichroism of the N-doped B36N cluster shifts to a longer wavelength compared with that of the B36 cluster.

Size-dependent dual emission of Cu,Mn:ZnSe QDs: Controlling both emission wavelength and intensity.

Cu,Mn:ZnSe quantum dots (QDs) of tunable size, controllable photoluminescence (PL) intensity ratio and PL range were prepared. A study of the experimental conditions confirmed that the size of Cu,Mn:ZnSe QDs is affected by the pH of the solution, the speed at which the Zn solution is injected and the reaction temperature. In general, high pH, low injection speed and high reaction temperature are optimal for preparing large QDs. Based on this knowledge, different sizes of Cu,Mn:ZnSe QDs were synthesized. Moreover, white emission Cu,Mn:ZnSe QDs were designed by controlling the experimental conditions and the feeding mole ratio of Mn:Cu.

Joint effect of ferromagnetic and non-ferromagnetic cations for adjusting room temperature ferromagnetism of highly luminescent CuNiInS quaternary nanocrystals.

In this work, highly luminescent quaternary CuNiInS nanocrystals (NCs) are put forward as a good prototype for investigating defect-induced room temperature ferromagnetism. A ferromagnetic Ni cation can preserve the strong luminescence of NCs without introducing intermediate energy levels in the center of the forbidden band. The strong luminescence of NCs is used as an indicator for monitoring the concentration of vacancy defects inside them, facilitating the investigation of the origin of room temperature ferromagnetism in CuNiInS NCs. Our results reveal that the patching of Cu vacancies [Formula: see text] with Ni will result in bound magnetic polarons composed of both [Formula: see text] and a substitution of Cu by Ni [Formula: see text] giving rise to the room temperature ferromagnetism of CuNiInS NCs. Either the ferromagnetic Ni or the non-ferromagnetic Cu cation can tune the magnetism of CuNiInS NCs because of the change of bound magnetic polaron concentration at the altered concentration ratio of [Formula: see text] and [Formula: see text].

Coherent Control of Optical Spin-to-Orbital Angular Momentum Conversion in Metasurface.

Efficient control over the conversion of optical angular momentum from spin to orbital form in a metasurface system is achieved. Under coherent symmetric incidence, it can support nearly 100% conversion and unitary output, while it can support 50% conversion with 25% transmittance under one beam incidence.

Controlling the morphology and optoelectronic properties of graphene hybrid materials by porphyrin interactions.

An approach to reversibly control the curling and unfolding of graphene hybrid materials by porphyrin interactions on the basal planes of graphene has been developed, and the curled graphene hybrid materials have enhanced photoelectrochemical and optical limiting performance.