Generation and characteristics of hollow structured optical fields based on multiple off-axis vortices.

In this paper, various hollow structured optical fields are generated by skillfully adjusting the number and positions of multiple off-axis vortices loaded in a Gaussian beam. The focal-field characteristics of the generated hollow structured optical fields after passing through an ordinary lens are studied based on the scalar diffraction theory. Firstly, a variety of hollow structured optical fields are theoretically simulated by adjusting the number and positions of multiple off-axis vortices loaded in the Gaussian beam. The focal-field characteristics of the hollow structured optical fields after passing through a lens are theoretically analyzed. On this basis, the experiments are implemented in the built optical system for multi-off-axis vortex beam focusing through an ordinary lens. In the experiments, various hollow structured optical fields are detected in CCD which are consistent with the theoretical results. The manipulations of size and rotation direction of the hollow structured optical fields are realized. We believe that this study will contribute to extending the potential applications of off-axis vortex beams in fields such as optical field shaping, optical manipulation and laser processing.

Underwater polarization imaging for visibility enhancement of moving targets in turbid environments.

Polarization imaging techniques have more prominent advantages for imaging in strongly scattered media. Previous de-scattering methods of polarization imaging usually require the priori information of the background region, and rarely consider the effect of non-uniformity of the optical field on image recovery, which not only reduces the processing speed of imaging but also introduces errors in image recovery, especially for moving targets in complex scattering environments. In this paper, we propose a turbid underwater moving image recovery method based on the global estimation of the intensity and the degree of polarization (DOP) of the backscattered light, combined with polarization-relation histogram processing techniques. The full spatial distribution of the intensity and the DOP of the backscattered light are obtained by using frequency domain analysis and filtering. Besides, a threshold factor is set in the frequency domain low-pass filter, which is used to adjust the execution region of the filter, which effectively reduces the error in image recovery caused by estimating the DOP of the backscattered light as a constant in traditional methods with non-uniform illumination. Meanwhile, our method requires no human-computer interaction, which effectively solves the drawbacks that the moving target is difficult to be recovered by traditional methods. Experimental studies were conducted on static and moving targets under turbid water, and satisfactory image recovery quality is achieved.

Distinguishing between halogenated alkanes containing the same halogen based on the reaction kinetic parameter using negative ion mobility spectrometry at atmospheric pressure.

Electron adsorption ionization ion mobility spectrometry can be used to detect halogen-containing volatile organic compounds with high sensitivity. However, this traditional electron attachment detection method cannot distinguish between volatile organic compounds containing the same halogen. For different organic compounds containing the same halogen, the product ions formed by the dissociation electron attachment process are the same. In this article, we propose a novel negative corona discharge ion mobility spectrometry method to distinguish between and detect halogenated alkanes containing the same halogen according to the different electron attachment rates and reaction kinetic parameters of the different halogenated alkanes. Although these halogenated alkanes, which contain the same halogen, produce the same type of ions through the electron attachment process, their electron attachment rates are different from each other. In this work, the kinetic information is used as the fingerprint information for the tested samples to distinguish different halogenated alkanes. Five halogenated alkanes were successfully detected using this method. The results show that the method based on the electron attachment rate constant is feasible for the determination of halogenated alkanes containing the same halogen.

Self-assembled MoS2/rGO nanocomposites with tunable UV-IR absorption.

MoS2/reduced graphene oxide (rGO) nanocomposites were synthesized using an ultrasonic pretreatment with a single-stage hydrothermal and reduction process. Self-assembled MoS2 layers in the rGO matrix were obtained. The effect of quantum confinement in the structure, controlled by the degree of reduction of graphene oxide and the size of the 2D MoS2 nanocrystals, made it possible to obtain tunable optical absorption. MoS2/rGO layered nanocomposites exhibit a wide UV-IR absorption in the wavelength range from 280 nm to 973 nm, which is attractive for highly efficient multiband solar cells and advanced photonics.

Experimental study on optical image encryption with asymmetric double random phase and computer-generated hologram.

Optical image encryption, especially double-random-phase-based, is of great interest in information security. In this work, we experimentally demonstrate the security and feasibility of optical image encryption with asymmetric double random phase and computer-generated hologram (CGH) by using spatial light modulator. First of all, the encrypted image modulated by asymmetric double random phase is numerically encoded into real-value CGH. Then, the encoded real-value CGH is loaded on the spatial light modulator and optically decrypted in self-designed experimental system. Experimental decryption results are in agreement with numerical calculations under the prober/mistaken phase keys condition. This optical decryption technology opens a window of optical encryption practical application and shows great potential for digital multimedia product copyright protection and holographic false trademark.