Zhao L, Duan Wenhui, Yelin S F
Department of Physics, Tsinghua University, Beijing, China.
Opt Express. 2011 Jan 17;19(2):981-93. doi: 10.1364/OE.19.000981.
We theoretically explore an all-optical method for generating tunable diffractive Fresnel lenses in coherent media based on electromagnetically induced transparency. In this method, intensity-modulated images in coupling light fields can pattern the coherent media to induce the desired modulo-2π quadratic phase profiles for the lenses to diffract probe light fields. We characterize the focusing and imaging properties of the induced lenses. In particular, we show that the images in coupling fields can flexibly control the images in probe fields by diffraction, where large focal length tunability from 1 m to infinity and high output (∼ 88% diffraction efficiency) can be achieved. Additionally, we also find that the induced Fresnel lenses can be rapidly modulated with megahertz refresh rates using image-bearing square pulse trains in coupling fields. Our proposed lenses may find a wide range of applications for multimode all-optical signal processing in both the classical and quantum regimes.
我们从理论上探索了一种基于电磁诱导透明性在相干介质中生成可调谐衍射菲涅耳透镜的全光方法。在这种方法中，耦合光场中的强度调制图像可以对相干介质进行图案化，以诱导透镜所需的模2π二次相位分布，从而使探测光场发生衍射。我们对诱导透镜的聚焦和成像特性进行了表征。特别地，我们表明耦合场中的图像可以通过衍射灵活地控制探测场中的图像，在此可以实现从1米到无穷大的大焦距可调性以及高输出（~88%的衍射效率）。此外，我们还发现，使用耦合场中携带图像的方脉冲序列，可以以兆赫兹刷新率对诱导菲涅耳透镜进行快速调制。我们提出的透镜可能在经典和量子领域的多模全光信号处理中找到广泛的应用。
