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表面等离子体透镜(PL)具有优异的光聚束效应,能够形成突破衍射极限的近场光斑,具有广泛的应用前景.为了获得较小的近场光斑,需要选用较短波长的激光入射.选用355 nm径向偏振光作为入射条件,使用COMSOL多物理场耦合仿真软件优化了同心圆环沟槽型PL的结构参数.结果显示,当圆环沟槽半径与槽间距都与表面等离子激元(SPPs)波的波长相等,且增加同心圆环槽数时,SPPs波在PL中心能形成相长干涉,可以获得较大的光增强效应;随着金属膜厚和槽宽的增加,中心处光强先增大后减小,存在最优值.使用聚焦离子束(FIB)加工制备了所设计的PL结构,加工结果具有较好的尺寸精度,但沟槽截面存在一定的锥度.进一步的仿真结果表明,沟槽横截面的小锥度对PL的聚束效应和光增强效应影响较小.
The surface plasmon lens (PL) has excellent optical bunching effect and can form a near-field spot that has a diffraction limit, and has wide application prospects. In order to obtain a smaller near-field spot, a shorter wavelength laser should be selected for use. 355 nm radial polarized light as the incident condition, the structural parameters of the concentric ring grooved PL were optimized using the COMSOL multiphysics coupled simulation software. The results show that when both the ring groove radius and the groove spacing are close to that of the surface plasmon polariton SPPs) wave are equal, and increasing the number of concentric ring slots, the SPPs wave can form constructive interference in the center of PL, and a larger light enhancement effect can be obtained. With the increase of metal film thickness and groove width, the central light The first increases and then decreases, there is an optimal value. The designed PL structure was fabricated by FIB, the processing result has better dimensional accuracy, but the groove cross section has a certain degree of taper.Further simulation The results show that the small taper of groove cross section has little effect on the bunching effect and light enhancement effect of PL.