Yanjun Han

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A feedback modification method based on variable separation mapping is proposed in the design of free-form optical system with uniform illuminance for LED source. In this method, the non-negligible size of LED source is taken into account, and a smooth optical system is established with single freeform surface regenerated by adding feedback to the lens(More)
A systematic method is proposed for designing an optical system for road lighting using an LED and a freeform lens that is optimized to produce a certain luminance distribution on the road surface. The proposed design method takes account of the luminance characteristics of the road surface, the energy efficiency of the system, the glare problem of the(More)
A combined feedback design method based on variable separation mapping is proposed in this paper to design free-form optical systems for an extended LED source with complicated illumination patterns. In this method, macro energy division and micro illuminance distribution feedback modifications are carried out according to the deviation between the(More)
Taking color quality scale (CQS) as color rendering assessment criterion, the parameters including each color LED's peak wavelength λi and fractional radiant flux Ii are optimized using genetic algorithm to maximize the luminous efficacy of radiation (LER) of the spectral power distributions (SPDs) of multi-color white light source with 3 to 7 components(More)
The freeform optical system plays a key role in illumination engineering, and several methods have been reported to manage the design of such system. In this paper, an approach to generate the polar-grids based flux transportation mapping for an arbitrarily-shaped target is proposed based on the conventional variable separation method. The source emitting(More)
Xianwen Liu,1 Changzheng Sun,1, ∗ Bing Xiong,1 Lai Wang,1 Jian Wang,1 Yanjun Han,1 Zhibiao Hao,1 Hongtao Li,1 Yi Luo,1 Jianchang Yan,2 Tongbo Wei,2 Yun Zhang,2 and Junxi Wang2 1Tsinghua National Laboratory for Information Science and Technology, State Key Lab on Integrated Optoelectronics, Department of Electronic Engineering, University, Beijing 100084,(More)
Designing an illumination system for a surface light source with a strict compactness requirement is quite challenging, especially for the general three-dimensional (3D) case. In accordance with the two key features of an expected illumination distribution, i.e., a well-controlled boundary and a precise illumination pattern, a two-step design method is(More)
Indium tin oxide (ITO)/ indium oxide (In<sub>x</sub>O) double layer structure was adopted as the transparent conduction and light scattering function layer to improve the light extraction efficiency of the GaN-based blue LEDs. The double layer structure was first deposited in one run by electron beam evaporation using ITO and Indium as the source(More)
We demonstrate aluminum nitride (AlN) on sapphire as a novel platform for integrated optics. High-confinement AlN microring resonators are realized by adopting a partially etched (pedestal) waveguide to relax the required etching selectivity for exact pattern transfer. A wide taper is employed at the chip end facets to ensure a low fiber-to-chip coupling(More)
An all-optically tunable microwave photonic phase shifter is demonstrated based on an epitaxial aluminum nitride (AlN) microring with an intrinsic quality factor of 3.2×10<sup>6</sup>. The microring adopts a pedestal structure, which allows overcoupling with 700 nm gap size and facilitates the fabrication process. A phase shift for broadband signals from 4(More)