光学
多模光纤
折射率
光子学
计算机科学
材料科学
光纤
物理
作者
Nicolas Barré,Alexander Jesacher
出处
期刊:Optics Express
[Optica Publishing Group]
日期:2022-03-15
卷期号:30 (7): 10573-10573
被引量:10
摘要
Graded-index optical elements are capable of shaping light precisely and in very specific ways. While classical freeform optics uses only a two-dimensional domain such as the surface of a lens, recent technological advances in laser manufacturing offer promising prospects for the realization of arbitrary three-dimensional graded-index volumes, i.e. transparent dielectric substrates with voxel-wise modified refractive index distributions. Such elements would be able to perform complex light transformations on compact scales. Here we present an algorithmic approach for computing 3D graded-index devices, which utilizes numerical beam propagation and error reduction based on gradient descent. We present solutions for millimeter-sized elements addressing important tasks in photonics: a mode sorter, a photonic lantern and a multimode intensity beam shaper. We further discuss suitable cost functions for all designs to be used in the algorithm. The 3D graded-index designs are spatially smooth and require a relatively small refractive index range in the order of $10^{-2}$, which is within the reach of direct laser writing manufacturing processes such as two-photon polymerization.
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