集成超表面模式转换的全光纤柱矢量MOPA激光器

All-fiber cylindrical vector beam MOPA laser based on integrated metasurface mode convertor

柱矢量光束因其独特的偏振分布特性而在光镊、高分辨率成像、遥感、等离子体聚焦等领域发挥着重要作用。为实现全光纤高功率柱矢量MOPA激光器,采用自主设计基于集成超表面的模式转换光纤器件,进行了理论分析与实验验证。自主设计集成超表面的模式转换光纤器件可直接稳定输出数瓦功率的径向偏振柱矢量种子光,且输出模式纯度可达95%以上。实验中通过降低弯曲损耗并对模式进行控制,获得了单级放大输出功率为52.2 W的径向偏振柱矢量光稳定输出,且模式光场分布在输出功率增加过程中并未出现明显变化。为进一步分析输出的模式特性,采用旋转检偏器的方法检测输出光的偏振特性及偏振纯度,并利用非相干模式叠加方法计算了输出的径向偏振柱矢量光的模式纯度。结果表明,集成超表面模式转换的全光纤柱矢量MOPA激光器在最大输出功率情况下,输出光的偏振纯度约为95.2%,模式纯度约为94%,验证了该全光纤方案的可行性。

Driven by the unique polarization distribution characteristics,cylindrical vector beams play an important role in optical tweezers,high resolution imaging,remote sensing,plasma focusing,and other related fields.To realize all-fiber high-power cylindrical vector beams MOPA laser,a mode conversion fiber device based on integrated metasurface is independently designed,whose feasibility is analyzed and verified in this demonstration.The self-designed integrated metasurface mode conversion fiber device can act as a radially polarized vector beam seed with several watts,and the mode purity is more than 95%.In the experiment,a radially polarized vector beam with an output power of 52.2 W was achieved in the case of a single-stage amplifier by decreasing bending loss and controlling the mode.Moreover,the mode field distribution was maintained well during the amplification.To further analyze the obtained mode characteristics,a rotatable polarizer method was used to measure the polarization characteristics and polarization purity,and the mode purity was measured by an incoherent mode superposition method.The results show that the polarization purity of the radially polarized vector beam is approximately 95.2%and the mode purity is about 94%with the maximum output power,which verify the feasibility of the all-fiber scheme.