Research output: Contribution to journal › Article › peer-review
Ultrahigh Numerical Aperture Metalens at Visible Wavelengths. / Liang, Haowen; Lin, Qiaoling; Xie, Xiangsheng; Sun, Qian; Wang, Yin; Zhou, Lidan; Liu, Lin; Yu, Xiangyang; Zhou, Jianying; Krauss, Thomas F.; Li, Juntao.
In: Nano Letters, Vol. 18, No. 7, 11.07.2018, p. 4460-4466.Research output: Contribution to journal › Article › peer-review
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TY - JOUR
T1 - Ultrahigh Numerical Aperture Metalens at Visible Wavelengths
AU - Liang, Haowen
AU - Lin, Qiaoling
AU - Xie, Xiangsheng
AU - Sun, Qian
AU - Wang, Yin
AU - Zhou, Lidan
AU - Liu, Lin
AU - Yu, Xiangyang
AU - Zhou, Jianying
AU - Krauss, Thomas F.
AU - Li, Juntao
N1 - © 2018 American Chemical Society. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details
PY - 2018/7/11
Y1 - 2018/7/11
N2 - Subwavelength imaging requires the use of high numerical aperture (NA) lenses together with immersion liquids in order to achieve the highest possible resolution. Following exciting recent developments in metasurfaces that have achieved efficient focusing and novel beam-shaping, the race is on to demonstrate ultrahigh-NA metalenses. The highest NA that has been demonstrated so far is NA = 1.1, achieved with a TiO2 metalens and back-immersion. Here, we introduce and demonstrate a metalens with a high NA and high transmission in the visible range, based on crystalline silicon (c-Si). The higher refractive index of silicon compared to TiO2 allows us to push the NA further. The design uses the geometric phase approach also known as the Pancharatnam-Berry (P-B) phase, and we determine the arrangement of nanobricks using a hybrid optimization algorithm (HOA). We demonstrate a metalens with NA = 0.98 in air, a bandwidth (full width at half-maximum, fwhm) of 274 nm, and a focusing efficiency of 67% at 532 nm wavelength, which is close to the transmission performance of a TiO2 metalens. Moreover, and uniquely so, our metalens can be front-immersed into immersion oil and achieve an ultrahigh NA of 1.48 experimentally and 1.73 theoretically, thereby demonstrating the highest NA of any metalens in the visible regime reported to the best of our knowledge. The fabricating process is fully compatible with microelectronic technology and therefore scalable. We envision the front-immersion design to be beneficial for achieving ultrahigh-NA metalenses as well as immersion metalens doublets, thereby pushing metasurfaces into practical applications such as high resolution, low-cost confocal microscopy and achromatic lenses.
AB - Subwavelength imaging requires the use of high numerical aperture (NA) lenses together with immersion liquids in order to achieve the highest possible resolution. Following exciting recent developments in metasurfaces that have achieved efficient focusing and novel beam-shaping, the race is on to demonstrate ultrahigh-NA metalenses. The highest NA that has been demonstrated so far is NA = 1.1, achieved with a TiO2 metalens and back-immersion. Here, we introduce and demonstrate a metalens with a high NA and high transmission in the visible range, based on crystalline silicon (c-Si). The higher refractive index of silicon compared to TiO2 allows us to push the NA further. The design uses the geometric phase approach also known as the Pancharatnam-Berry (P-B) phase, and we determine the arrangement of nanobricks using a hybrid optimization algorithm (HOA). We demonstrate a metalens with NA = 0.98 in air, a bandwidth (full width at half-maximum, fwhm) of 274 nm, and a focusing efficiency of 67% at 532 nm wavelength, which is close to the transmission performance of a TiO2 metalens. Moreover, and uniquely so, our metalens can be front-immersed into immersion oil and achieve an ultrahigh NA of 1.48 experimentally and 1.73 theoretically, thereby demonstrating the highest NA of any metalens in the visible regime reported to the best of our knowledge. The fabricating process is fully compatible with microelectronic technology and therefore scalable. We envision the front-immersion design to be beneficial for achieving ultrahigh-NA metalenses as well as immersion metalens doublets, thereby pushing metasurfaces into practical applications such as high resolution, low-cost confocal microscopy and achromatic lenses.
KW - crystalline silicon
KW - Dielectric metalens
KW - high numerical aperture
KW - oil immersion
UR - http://www.scopus.com/inward/record.url?scp=85049264651&partnerID=8YFLogxK
U2 - 10.1021/acs.nanolett.8b01570
DO - 10.1021/acs.nanolett.8b01570
M3 - Article
AN - SCOPUS:85049264651
VL - 18
SP - 4460
EP - 4466
JO - Nano Letters
JF - Nano Letters
SN - 1530-6984
IS - 7
ER -