设计了一种适合集成的基于介质超表面的透射式光束偏转器, 可在1 550 nm附近的红外波段实现大角度偏转, 同时具有宽光谱、高效率的优势。根据广义斯涅尔定律设计并优化了光束偏转器的结构, 由横截面为梯形的非晶硅纳米柱周期性排列在石英玻璃衬底上构成, 相比于传统超表面采用多个纳米柱实现离散的相位梯度, 梯形纳米柱形成的连续相位梯度可以获得更好的偏转特性。利用时域有限差分算法对光束偏转器的效率、偏转角、宽光谱和入射角度依赖性等性能进行了仿真分析, 采用电子束光刻等工艺制备加工出上述器件并进行了测试。仿真结果表明: 偏转器在1 350~1 650 nm波段均具备良好的偏转特性, 平均透射率高于87%, 平均偏转率为81%; 器件在1 550 nm处实现了42.8°的大偏转角, 透射率为84%, 偏转率为80%, 且允许入射角度在-10°~5°变化。实验测试结果表明: 对于1 550 nm波长, 光束偏转角度在41°附近, 器件透射率约为76%, 约35%的入射光偏转到目标角度。上述方案为近红外超表面器件的设计提供了新的思路, 实现了效率、偏转角和适用波长的优化, 透射式光路更加适合集成, 应用潜力更大。

For the infrared band near 1 550 nm, a transmissive beam deflector based on a dielectric metasurface is proposed. This deflector can achieve a large deflection angle together with a broadband spectrum and high efficiency. The structural design of the deflector is optimized according to the generalized Snells law. It comprises amorphous silicon nanopillars with trapezoidal cross sections that are arranged periodically on a quartz glass substrate. The continuous phase gradient formed by the unique trapezoidal nanopillars in the proposed structure provides superior deflection characteristics compared with those provided by the discrete phase gradient formed by the discrete nanopillars utilized in traditional metasurfaces. The performance of the proposed device is simulated and analyzed with respect to efficiency, deflection angle, wavelength dependence, and incident angle dependence using the finite-difference time-domain method. The performance of this device is tested after its fabrication via processes such as electron beam lithography. The simulations indicate that this deflector realizes a deflection angle as large as 42.8° at 1 550 nm, as well as a transmissivity of 84%, a deflection efficiency of 80%, and an allowance of incident angle between -10° and 5°. Moreover, the deflector exhibits impressive deflection characteristics for wavelengths ranging from 1 350—1 650 nm, with an average transmissivity exceeding 87% and an average deflection efficiency of 81%. Experimental test results show that, at the wavelength of 1 550 nm, the beam deflection angle is nearly 41°, the device transmissivity is approximately 76%, and approximately 35% of the incident light is deflected to the target angle. The proposed device represents a new approach for the design of near-infrared metasurface devices and has application potential in numerous fields.