基于聚合物材料的回音壁模式卵形微腔,打破了传统微腔的圆对称性,利用微腔边缘波长级的缺口,实现了远场发散角极小的定向出射。通过三维时域有限差分法仿真分析了卵形微腔的回音壁模式及定向输出特性,重点讨论了不同的变形参数对于远场特性的影响。选用最优的变形参数,得到了波长在536 nm附近的回音壁模式的近场、远场的光场分布特性,以及缺口尺寸对微盘输出光谱的影响,并将卵圆形微盘结构拓展到卵体形微球结构,进一步缩小了光束发散角(约为2.5°),其最高的定向出射效率达93%。该结构不仅可以作为光与物质相互作用的新颖的研究平台,拓展了缺陷变形微腔在定向出射领域的研究范畴,而且有利于推动微型光子器件在生物医学及环境检测等领域的发展。

In this paper, a whispering-gallery-mode (WGM) oval-shaped microcavity based on polymers was proposed, breaking the circular symmetry of traditional microcavities, and its wavelength-level notch on the boundary achieved unidirectional emission at an extremely low far-field divergence angle. In addition, the three-dimensional finite-difference time-domain method was used to investigate the WGM and unidirectional emission performances of the proposed microcavity, especially the influence of different deformation parameters on the far-field properties. With the optimal deformation parameters, the WGM near- and far-field performances of light field distribution near the wavelength of 536 nm were obtained. Besides, the effect of notch size on the output spectrum of the proposed microdisk was also analyzed. Then, extending the oval microdisk to an ovoid microsphere further reduced the beam divergence (~2.5°), with the highest unidirectional emission efficiency being 93%. Therefore, the proposed structure can function well as an excellent platform to explore the light-matter interaction, expand the research range of notched microcavities in the field of unidirectional emission, and promote the development of photonic microdevices in the fields of biomedicine and environmental detection.