Engelberg Jacob, Levy Uriel
Department of Applied Physics, The Center for Nanoscience and Nanotechnology, The Hebrew University, Jerusalem 91904, Israel.
Nanophotonics. 2022 Jul 14;11(16):3559-3574. doi: 10.1515/nanoph-2022-0196. eCollection 2022 Sep.
A plethora of metalenses and diffractive lenses ("flat lenses") have been demonstrated over the years. Recently, attempts have been made to stretch their performance envelope, particularly in the direction of wide-band achromatic performance. While achromatic behavior has been demonstrated, showing an actual improvement in imaging performance relative to conventional (non-chromatically corrected) flat lenses has remained a major challenge. The reasons for this are use of inappropriate performance metrics, lack of comparison to a baseline conventional design, and lack of a performance metric that combines signal-to-noise ratio and resolution. An additional problem is that different published flat lens designs use different first order parameters, so they cannot be compared. In this work we present an overall performance metric that will allow comparison of different types of flat lenses, even if their first order optical parameters are not the same. We apply this metric to several published achromatic flat lens designs and compare them to the equivalent conventional flat lens, which we consider as the lower bound for achromatic flat lens performance. We found that the performance of the achromatic flat lenses studied does not surpass that of a conventional diffractive lens. Use of this metric paves the way for future developments in the field of achromatic flat lenses, which will display proven progress.
多年来，人们已经展示了大量的超透镜和衍射透镜（“平面透镜”）。最近，人们试图拓展它们的性能范围，特别是在宽带消色差性能方面。虽然已经证明了消色差行为，但相对于传统（非消色差校正）平面透镜，在成像性能上显示出实际的提升仍然是一个重大挑战。其原因包括使用了不恰当的性能指标、缺乏与基线传统设计的比较以及缺乏结合信噪比和分辨率的性能指标。另一个问题是，不同发表的平面透镜设计使用不同的一阶参数，因此无法进行比较。在这项工作中，我们提出了一种整体性能指标，即使不同类型平面透镜的一阶光学参数不同，也能对它们进行比较。我们将这个指标应用于几种已发表的消色差平面透镜设计，并将它们与等效的传统平面透镜进行比较，我们将传统平面透镜视为消色差平面透镜性能的下限。我们发现，所研究的消色差平面透镜的性能并未超过传统衍射透镜。使用这个指标为消色差平面透镜领域的未来发展铺平了道路，这将展示出已证实的进展。
