Yan Ying-Bai

Rigorous concept for the analysis of diffractive lenses with different axial resolution and high lateral resolution

We present a rigorous electromagnetic design and analysis of two-dimensional diffractive lenses (DLs) with different axial resolution and high lateral resolution. Without paraxial approximation, focusing characteristics of two kinds of DL, one with a long focal depth and a high lateral resolution, the other with high axial resolution and high lateral resolution, for f-numbers of 0.6, 1.0, 1.5, and 2.0 have been determined including the actual focal depth, the ratio between the focal depth of the designed DL and the focal depth of the conventional quadratic lens, and the spot size of the central lobe at the actual focal plane. Numerical and graphic results show that the designed DLs indeed have a long focal depth and a high lateral resolution, or high axial resolution and high lateral resolution by use of different preset focal depths.

Rigorous electromagnetic design of finite-aperture diffractive optical elements by use of an iterative optimization algorithm

We propose a rigorous electromagnetic design of two-dimensional and finite-aperture diffractive optical elements (DOEs) that employs an effective iterative optimization algorithm in conjunction with a rigorous electromagnetic computational model: the finite-difference time-domain method. The iterative optimization process, the finite-difference time-domain method, and the angular spectrum propagation method are discussed in detail. Without any approximation based on the scalar theory, the algorithm can produce rigorous design results, both numerical and graphical, with fast convergence, reasonable computational cost, and good design quality. Using our iterative algorithm, we designed a diffractive cylindrical lens and a 1-to-2-beam fanner for normal-incidence TE-mode illumination, thus showing that the optimization algorithm is valid and competent for rigorously designing diffractive optical elements. Concerning the problem of fabrication, we also evaluated the performance of the DOE when the DOE profile is discrete.

Optical Wavelet Packet Transform

We employ optical wavelet packet transform (OWPT) to propose an opto-electronic system based on volume holography to select the best bases of image banks for image compression, because of the superior processing ability to optical wavelet transform and the potentiality in new application fields. The simulation results show that the best bases chosen are the same as the bases selected by discrete wavelet packet transform (DWPT). Because DWPT is time consuming, especially when the volume of image bank is very large, processing time can be greatly shortened by OWPT.

Iterative optimization algorithm based on electromagnetic model for designing diffractive micro-optical elements

Abstract An iterative optimization algorithm for designing two dimensions, finite aperture, aperiodic diffractive micro-optical elements based on rigorous electromagnetic computation model––the finite-difference time-domain method has been proposed. All aspects relating to the algorithm such as the finite-difference time-domain method, and the optimization process have been discussed in detail. Without any approximation based on scalar theory, the algorithm can present rigorous design results with reasonable computational cost. An aspherical surface lens and four kinds of off-axis lenses for normally incident TE mode have been designed to illustrate our algorithm. Meanwhile, we also consider the influence of quantized-lenses profiles on their diffraction performance.

Designing diffractive phase plates for beam smoothing in the fractional Fourier domain

A new modification of the output plane constraint is used in the iterative algorithm for designing diffractive phase plates (DPPs) to produce spatial beam smoothing in the fractional Fourier (FRT) domain. Compared with previously published algorithms, this algorithm can provide faster convergence, more powerful ability to overcome the local minimum problem and better smoothing quality. By computer simulation, it has shown that the DPP designed by this algorithm has the advantages of high uniformity at the main lobe, low profile error and steep edge.

Making CGH By Using Electron Beam

The Electron-beam Lithography is a newly developed microfabrication technique. The principle and technology of making CGH by E-beam were discussed. The influences of error on the E-beam Generated Holograms have been analysed. The experimental results of the differential filters and a CGH scatter-plate have also been presented.