Thin film optical elements exhibiting translational invariance, and thus robustness to optical misalignment, are crucial for rapid development of compact and integrated optical devices. In this letter, we experimentally demonstrate a beam-shaping element that generates an annular beam by spatially filtering the fundamental Gaussian mode of a laser beam. The element comprises of a one-dimensional photonic crystal cavity fabricated using sputtered thin films. The planar architecture and in-plane symmetry of the element render our beam-shaping technique translationally invariant. The generated annular beam is sensitive to the polarization direction and the wavelength of the incident laser beam. Using this property of the annular beam, we show simultaneous generation of concentric annular beams of different wavelengths. Our experimental observations show an excellent agreement with simulation results performed using finite-difference time-domain method. Such a beam-shaping element has applications in areas ranging from microscopy and medicine to semiconductor lithography and manufacturing in microelectronics industry.

中文翻译：

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使用薄膜的环形梁平移不变生成

薄膜光学元件表现出平移不变性，从而对光学未对准具有鲁棒性，对于紧凑型和集成光学器件的快速开发至关重要。在这封信中，我们通过实验演示了一种光束整形元件，该元件通过空间过滤激光束的基本高斯模式来产生环形光束。该元件包括使用溅射薄膜制造的一维光子晶体腔。元件的平面结构和平面内对称性使我们的光束整形技术具有平移不变性。产生的环形光束对入射激光束的偏振方向和波长很敏感。使用环形光束的这种特性，我们展示了同时产生不同波长的同心环形光束。我们的实验观察显示与使用有限差分时域方法执行的模拟结果非常吻合。这种光束整形元件的应用范围从显微镜和医学到半导体光刻和微电子行业的制造。