Xing Zhao

Bio: Xing Zhao is an academic researcher from Nankai University. The author has contributed to research in topics: Integral imaging & Image processing. The author has an hindex of 11, co-authored 39 publications receiving 259 citations. Previous affiliations of Xing Zhao include Hong Kong Polytechnic University.

Modified optical vortices for encoding topological charges with principal-sidelobe ring relationships

Abstract: We study modified optical vortices for encoding topological charges based on radius ratios between principal and the modified first sidelobe rings. The method is immune to harassments from alignment and phase matching between the beams and optical elements. Moreover, it is demonstrated that the radius ratios and their corresponding modulation parameters are independent to wavelength and size of the spiral phase mask.

A single mirror magnifier with freeform surfaces using radial basis functions based on surface slope

Abstract: It is of great importance to utilize a model to characterize the surfaces while designing an optical imaging system with freeform surfaces. For this purpose, a model with radial basis function based on surface slope (RBF-slope) for optical freeform surfaces was investigated by establishing the relationship between the shape factor and local surface slope, and improving the distributions of the basis functions for circular apertures. We performed the fitting experiment for “bumpy” paraboloids; the results demonstrated that the RBF-slope model has stronger fitting ability than conventional RBF model. A prototype of single mirror magnifier for head-worn display was designed and fabricated, in which the freeform mirror was described and characterized using the RBF-slope model. It can be proved by the design results that the RBF-slope model for optical freeform surfaces has obvious advantages in aberration balancing over conventional model. The primary experiments showed that the freeform surface was well fabricated and expected image display can be achieved.

Investigation of Focusing Properties on Astigmatic Gaussian Beams in Nonlinear Medium

Abstract: Ultra-short laser filamentation has been intensively studied due to its unique optical properties for applications in the field of remote sensing and detection. Although significant progress has been made, the quality of the laser beam still suffers from various optical aberrations during long-range transmission. Astigmatism is a typical off-axis aberration that is often encountered in the off-axis optical systems. An effective method needs to be proposed to suppress the astigmatism of the beam during filamentation. Herein, we numerically investigated the impact of the nonlinear effects on the focusing properties of the astigmatic Gaussian beams in air and obtained similar results in the experiment. As the single pulse energy increases, the maximum on-axis intensity gradually shifted from the sagittal focus to the tangential focus and the foci moved forward simultaneously. Moreover, the astigmatism could be suppressed effectively with the enhancement of the nonlinear effects, that is, the astigmatic difference and the degree of beam distortion were both reduced. Through this approach, the acoustic intensity of the filament (located at the tangential focal point) increased by a factor of 22.8. Our work paves a solid step toward the practical applications of the astigmatism beam as the nonlinear lidar.

Optimization method using nodal aberration theory for coaxial imaging systems with radial basis functions based on surface slope

Abstract: The radial basis functions based on the surface slope (RBF-Slope) freeform surfaces model has demonstrated stronger fitting ability and better optical performance than the conventional RBF model. However, the large number of basis functions and optimization variables of the RBF-Slope model may result in convergence problems during optimization for optical systems consisting of freeform surfaces characterized by RBF-Slope. To overcome these drawbacks, we use Zernike polynomials to link the RBF-Slope model to aberration correction and propose a new optimization method for coaxial imaging systems using the RBF-Slope model based on nodal aberration theory (NAT). The aberrations generated by the conic parameter and Zernike terms up to Z17/18 of the Zernike freeform surface at the non-stop surface in the coaxial imaging system are analyzed, and the gradient descent is implemented to obtain the optimal coefficients of the Zernike surface, which is then fitted by the RBF-Slope surface for further optimization. The method is applied to the optimization of a secondary mirror using the RBF-Slope model in a two-mirror telescope and proved to have better results than traditional commonly used direct optimization. This research offers an important reference for optimization using NAT and provides valuable insight into the optimization method for RBF-Slope freeform surfaces.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Generation of the "perfect" optical vortex using a liquid-crystal spatial light modulator

Abstract: We introduce the concept of the perfect optical vortex whose dark hollow radius does not depend on the topological charge. It is shown analytically and experimentally that such a vortex can be approximately generated in the Fourier transforming optical system with a computer-controlled liquid-crystal spatial light modulator.

Advances in ultra-precision machining of micro-structured functional surfaces and their typical applications

Abstract: Micro-structured functional surfaces have achieved widespread applications in various advanced scientific, technological, industrial, and engineered fields due to their excellent performances, which are vitally limited by their feasible fabrication. Currently, ultra-precision machining, typically including ultra-precision diamond turning, ultra-precision diamond milling, ultra-precision diamond scratching, ultra-precision grinding, and ultra-precision polishing, is developed as a very-promising solution for the micro-structured functional surface fabrication with high quality, high efficiency, high flexibility, and low cost. Therefore, this paper aims to briefly review the current state of the art in the investigation into ultra-precision machining characteristics of micro-structured functional surfaces with a focus on their typical advanced applications as the significant achievements of their ultra-precision machining fabrication, discuss the key challenges, and further provide new insights into ultra-precision machining of micro-structured functional surfaces for the future research and their further advanced applications.

Nanophotonic projection system.

Abstract: Low-power integrated projection technology can play a key role in development of low-cost mobile devices with built-in high-resolution projectors. Low-cost 3D imaging and holography systems are also among applications of such a technology. In this paper, an integrated projection system based on a two-dimensional optical phased array with fast beam steering capability is reported. Forward biased p-i-n phase modulators with 200MHz bandwidth are used per each array element for rapid phase control. An optimization algorithm is implemented to compensate for the phase dependent attenuation of the p-i-n modulators. Using rapid vector scanning technique, images were formed and recorded within a single snapshot of the IR camera.