Sandwich nano-fin to reduce the aspect ratio requirement of metasurface

Wei Lun Hsu, Chen Yi Yu, Hao Ting Lai, Yen Chun Chen, Chih Ming Wang

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


The current high-aspect-ratio Pancharatnam–Berry (PB)-phase metasurfaces in which vertical dimensions are much larger than the lateral dimensions are challenging to fabricate. Therefore, reducing the aspect ratio requirement has become a research priority. We propose a sandwich nano-fin consisting of GaN/amorphous silicon (a-Si)/GaN on a silica substrate to reduce the strict aspect ratio requirement of current PB-phase metasurfaces. The phase modulation ability and polarization conversion efficiency (PCE) of sandwich nano-fins were investigated. Compared with a conventional GaN nano-fin, the aspect ratio of sandwich nano-fin decreased from 6 to 4 under the same geometric dimension. The PCE of the sandwich nano-fin was up to 68.27%, 1.5 times higher than that of a GaN nano-fin under the same aspect ratio of 4. Moreover, after adding the a-Si layer, the overall PCE improved from 32.17 to 40.54% for the sandwich nano-fin. The sandwich structure simultaneously reduces the challenge of manufacturing and improves efficiency compared to current PB-phase metasurfaces.

Original languageEnglish
Pages (from-to)134-140
Number of pages7
JournalOptical Review
Issue number1
StatePublished - Feb 2023


  • Aspect ratio
  • Metasurface
  • Polarization conversion efficiency
  • Sandwich nano-fin


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