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中国物理学会期刊

基于猫眼逆反射器的大范围免调试激光器

CSTR: 32037.14.aps.72.20221956

Cat-eye retroreflectors based large-dynamic-range alignment-free laser

CSTR: 32037.14.aps.72.20221956
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  • 利用具有逆反射特性的光学元件构成激光器的谐振腔, 能够赋予激光器大范围免调试工作的潜力. 本文讨论了谐振激光自适应无线传能/通信等新兴应用对激光器免调试工作范围的要求, 设计了基于猫眼逆反射器的大范围免调试激光器, 采用腔内望远镜系统和复合腔结构分别拓展激光器的工作距离范围和提升激光安全性. 通过对激光谐振腔的稳定性分析和对猫眼逆反射器的像差分析, 明确了球差和场曲导致的猫眼离焦分别是限制免调试激光器工作距离和视场的关键因素. 实验中通过优化光学设计补偿像差, 实现了端面泵浦Nd:GdVO4激光器的大范围免调试运转. 16.6 W泵浦功率下, 激光器接收端在1—5 m工作距离范围内移动和在±30°接收端视场范围内转动时输出功率保持在5 W以上, 功率波动小于10%, 无需重新准直调节. 5 m工作距离下, 在4.6°发射端视场内输出功率保持在其最大值的50%以上, 对应接收端横向移动范围达到40 cm. 本工作明确了猫眼腔免调试激光器的设计优化原则, 为相关研究提供了实验结果参考.

     

    Lasers with cavities consisting of retroreflecting elements can give the potential for large-dynamic-range alignment-free operation, which makes the important applications in adaptive wireless laser power transfer/communication possible. In such an emerging approach based on resonant laser beam in the cavity, the laser is delivered to the photovoltaic cell for charging application (or photodiode for communication application) at the receiver automatically, without the necessity of positioning and aiming the receiver in conventional laser wireless power transfer techniques. The laser capable of operating alignment-free efficiently across large-dynamic-range is essential for the application. In this work, the requirements for the dynamic range of alignment-free operation are summarized. An alignment-free laser with a cavity consisting of cat-eye retroreflectors is designed, and a large alignment-free dynamic range as never before is experimentally demonstrated. Telescope system in the laser cavity is adopted to suppress the beam expansion to enhance the working distance between the laser transmitter and the receiver. Coupled cavity scheme is used to reduce the laser intensity between the transmitter and the receiver for laser safety. By calculating the stability zone of the laser cavity, it is found that the stability zone of the receiver cat-eye distance is quite narrow. Hence, the laser operation is very sensitive to the defocusing of the cat eye defocusing. Moreover, the cat eye defocusing induced by optical aberrations of spherical aberration and field curvature can be rather serious, when the long working distance results in a large beam size and the angle of incidence is large, hence limiting the effective working distance and the field of view of the alignment-free laser significantly. In the experiment, the improved optical designs with the aberrations compensation are adopted for large-dynamic-range alignment-free operation. The end-pumped Nd:GdVO4 laser at 1063 nm can deliver over 5-W output within a working distance range of 1–5 m, and a receiver field of view of ±30°, without cavity realignment. The transmitter field of view reaching 4.6° (full width at half maximum) at a working distance of 5 m is also realized, with a corresponding receiver transverse movement range of 40 cm. Our work clarifies the optimizing criteria of the large-dynamic-range alignment-free laser based on cat-eye retroreflectors.

     

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