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中国物理学会期刊

基于超构表面光栅反射镜的垂直腔面发射激光器

Vertical-Cavity Surface-Emitting Laser Based on Metasurface Grating Reflector

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  • 研究制备了采用超构表面光栅(MSG)作为高反射率耦合输出镜的垂直腔面发射激光器(VCSEL)。超构表面光栅由GaAs/AlOx构成,且光栅齿下包含一个与其同为GaAs材料的同质亚层,从而形成零对比度界面,可以有效降低界面应力,而且仿真结果表明其对MSG的反射特性具有调制作用。实验结果表明,MSG-VCSEL实现了室温下稳定的TE偏振激射,工作波长940 nm,阈值电流2mA,25mA时单模光功率1.76mW,且能够在整个工作范围内保持稳定的单模状态。这种与VCSEL同材料体系、结构简单的MSG,不仅便于器件的单片集成与微型化,更以锁偏振、单模态的稳定输出为光谱学、原子钟等精密计量场景提供核心性能保障。

     

    Vertical-Cavity Surface-Emitting Lasers (VCSELs) are widely used as light sources in optical communication, lidar, biomedicine, and 3D sensing due to their low threshold current, high modulation bandwidth, single longitudinal mode, and natural suitability for high-density two-dimensional integration. However, VCSELs have inherent limitations. When the oxide aperture exceeds 4 μm, multimode lasing is likely to occur, and their polarization performance remains poor. These issues hinder their use in applications such as quantum communication and atomic clocks. To overcome these limitations and enable device miniaturization, this study designs and fabricates a VCSEL incorporating a metasurface grating (MSG) as a high-reflectivity output mirror. The key innovation lies in an MSG structure compatible with the VCSEL material system. Composed of GaAs/AlOx, the structure incorporates a GaAs homogeneous sublayer beneath the grating teeth to reduce interface stress. This sublayer also significantly modulates the reflectivity characteristics of the MSG. Simulations based on the rigorous coupled-wave method determine the optimal parameter range for the TE-polarized MSG. The results indicate a high-reflection band of nearly 100 nm around 940 nm, along with strong polarization selectivity and angle sensitivity. These properties support stable single-mode device operation. Experimentally, MOCVD epitaxial growth, ICP dry etching, and one-step dual-domain oxidation are combined to achieve monolithic integration of the MSG and VCSEL. Tests show that the device achieves stable TE-polarized lasing at room temperature, with an operating wavelength of 940 nm, a threshold current of 2 mA, and a single-mode output power of 1.76 mW at 25 mA. Stable single-mode operation is maintained throughout. This study demonstrates that MSG simplifies the VCSEL structure and facilitates integration and miniaturization, aligning with low-cost development trends. It also addresses multimode lasing and poor polarization in conventional VCSELs, improves device stability, and lays the foundation for applications in high-precision fields, highlighting its theoretical and practical significance.

     

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