The dynamics of Airy beams modeled by the fractional Schrödinger equation (FSE) with the potential barrier are numerically investigated. Adjusting the Lévy index provides a convenient way to control the diffraction of Airy beams which presents the non-diffraction and splitting property. It has been found that the total reflection of beams occurs when the depth of the single potential barrier exceeds the threshold, and that the number of reflected waves is influenced by the Lévy index and the location of potential barrier. However, the periodic self-imaging phenomenon of Airy beams is shown under a symmetric potential barrier when the Lévy index is equal to one, and the self-imaging period of the asymmetric Airy beams is analytically demonstrated and is as twice as that of symmetric Gaussian beams, moreover, the chaoticon of light field is formed during propagation as the Lévy index increases. All the properties of Airy beams modeled by FSE confirm the potential application in optical manipulation.

Based on the extended Huygens-Fresnel principle, we have derived the analytical expression of the average intensity of optical coherence lattices (OCLs) in oceanic turbulence with anisotropy, and then the beam quality parameters including the Strehl ratio (S_R) and the power-in-the-bucket (PIB) are obtained. One can find that the OCLs will eventually evolve into Gaussian shape with the periodicity reciprocity gradually breaking down when propagating through the anisotropic ocean water, and that the trend of evolving into Gaussian can be accelerated for increasing the ratio of temperature and salinity contributions to the refractive index spectrum ω, the lattice constant a and the rate of dissipation of mean square temperature χ_T or decreasing the anisotropic factor ξ and the rate of dissipation of turbulent kinetic energy per unit mass of fluid ε. Further, the S_R and PIB in the target plane under the effects of oceanic parameters are discussed in detail, and the S_R and PIB can be increased for the larger ξ and ε or the smaller χ_T and ω, namely, the beam quality becomes better. Our results can find potential application in the future optical communication system in an oceanic environment.

In an imaging system, resolution and signal-to-noise ratio (SNR) are two important indexes to characterize imaging quality. Ghost imaging is a novel imaging method whose imaging resolution and SNR are affected by the speckle size. In this paper, the relation between speckle size and resolution as well as that between speckle size and SNR in the GI system is analyzed in detail. It is shown that the critical resolution, resolvable minimum-separation between two adjacent objects, is approximately equal to the speckle size (speckle diameter). There exists an optimum SNR when the speckle size is larger than the object size. Based on our conclusion, we propose a scheme to enhance the critical resolution of the GI system by using a vortex beam, and the enhancement ability under different topological charges is clearly presented, which can be quantized by a simple formula.

Research towards practical applications of ghost imaging lidar system especially in longer sensing distance has been urgent in recent years. In this paper we develop a ghost imaging lidar system to boost an extension of remote imaging, where the transmission distance of the collimated pseudo-thermal beam can be improved hugely over long range and just shifting the adjustable lens assembly generates wide field of view suiting for short-range imaging. Based on the proposed lidar system, the changing tendency of illuminating field of view, energy density, and reconstructed images is analyzed and verified experimentally. Some considerations on the improvement of this lidar system are also discussed.

Robot-assisted therapy is regarded as an effective and reliable method for the delivery of highly repetitive rehabilitation training in restoring motor skills after a stroke. This study focuses on the rehabilitation of fine hand motion skills due to their vital role in performing delicate activities of daily living (ADL) tasks. The proposed rehabilitation system combines an adaptive assist-as-needed (AAN) control algorithm and a Virtual Reality (VR) based rehabilitation gaming system (RGS). The developed system is described and its effectiveness is validated through clinical trials on a group of eight subacute stroke patients for a period of six weeks. The impact of the training is verified through standard clinical evaluation methods and measuring key kinematic parameters. A comparison of the pre- and post-training results indicates that the method proposed in this study can improve fine hand motion rehabilitation training effectiveness.

We have numerically investigated the propagation properties of ring Airy beams modeled by a fractional Schrödinger equation (FSE). Beam splitting is exhibited and clarified from the view of group delay. Compared with the case of the condition in free space, the focal intensity is greatly enhanced and presents a trend from increasing to decreasing with the decrement of the Lévy index, while the focal length largely increases; in addition, the parabolic trajectory is distorted with the Bessel pattern gradually disappearing. However, both the focal intensity and its length get decreased due to the absence of the initial phase of ring Airy beams; simultaneously, the size of the focal spot decreases for a larger Lévy index. The changes of focusing properties are clearly clarified. Moreover, without initial phase, the ratio of focal intensity under the Lévy index to the condition in free space is given to show the faster growth of focal intensity when the Lévy index is lower than 1.25; otherwise, the trend gets reversed. The autofocusing properties of ring Airy beams modeled by FSE can find applications in optical trapping and manipulation.