Click the "blue character" button above to subscribe recently. Professor Hu Wei and Professor Lu Yanqing of Nanjing University School of modern technology led the liquid crystal assembly to achieve a specific refractive index plane distribution by reasonably presetting the plane structure orientation of the liquid crystal, and prepared a homogeneous and anisotropic integrated photon element. Based on the temperature and incident polarization control, the functional tuning and switching of a single element are realized. Furthermore, it is expected to realize the dynamic series parallel connection of discrete components on chip by combining the fixed-point control of electric field, optical field and other external fields. The "soft" integrated photon element will provide a feasible solution for the programmable integrated photon chip. This achievement is titled with liquid crystal mediated active waveguides toward programmable integrated optics and published online in advanced optical materials on March 18, 2020 (adv. opt. Mater. 2020, 1902033).
Modern photon technology is developing towards miniaturization, integration, multi-function and self-adaptive. On chip integrated photon chips play an important role in the fields of optical information processing, optical communication and sensing. Optical waveguide is the basis of realizing the function and connection of all kinds of integrated photon elements. It controls the directional propagation of light by controlling the spatial refractive index distribution to achieve the total internal reflection of electromagnetic wave. Optical waveguides are usually realized by setting the microstructure or doping distribution of materials such as silicon, silicon dioxide, III-V family, lithium niobate and polymer. Traditional integrated photon chips are like block printing. Functional components and connecting waveguides are copied in large quantities with fixed structure and material composition. Therefore, the organizational structure and function of chips are fixed. Once local damage occurs, the function of the whole chip is also damaged. If we can realize the dynamic waveguide connection of discrete components, we can realize the programmable control of the photon chip (which can be compared with movable type printing), and enable the chip on demand, which can greatly improve the safety and reliability of the chip.
Aiming at this goal, the research team uses the optical orientation technology to precisely control the distribution of the liquid crystal in the direction vector plane to obtain the preset anisotropic refractive index spatial distribution, thus preparing a series of graded index waveguide elements based on the homogeneous liquid crystal materials. In this paper, we show a variety of integrated photon elements, such as straight / U-shaped waveguide, ring resonator and so on. Based on the intrinsic and external field stimulation response characteristics of such soft materials as liquid crystal, the team also realized the tuning and switching of waveguide function through thermal regulation and incident polarization change. The above design is also applicable to the photopolymer liquid crystal film material, which endows this kind of liquid crystal waveguide element with excellent flexibility. Through selective local polymerization, combined with fixed-point control of external fields such as electric field and optical field, it is expected to realize dynamic waveguide connection between fixed functional elements, thus providing a possible scheme for future programmable integrated photon chip.
Fig. 1a is a schematic diagram of the spatial distribution of the director of the liquid crystal waveguide; B is a temperature controlled liquid crystal direct waveguide switch;
c. D, integrated "soft" photon chip.
Wei Ting and Chen Peng, associate researchers of 17 level master students, CO authored the paper. Professor Hu Wei and Professor Lu Yanqing were the corresponding authors of the paper. Tang Mingjie, Wu Guangxing, Chen Zhaoxian, Shen Zhixiong, Ge Shijun, associate researchers and Professor Xu Fei made important contributions to the paper. Professor Jiang Xiaoshun gave constructive suggestions. The research was funded by national key research and development plan, natural science foundation, Provincial Outstanding Youth and other projects, and supported by platforms and projects such as the collaborative innovation center of artificial micro structure science and technology, the 100 thousand project of Nanjing University, and the basic scientific research business fees of Central University.
Paper link:
https://onlinelibrary.wiley.com/doi/abs/10.1002/adom.201902033
Source: College of modern engineering and Applied Sciences, Nanjing University
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