期刊
ADVANCED MATERIALS
卷 34, 期 23, 页码 -出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/adma.202105590
关键词
alpha-MoO3; hyperbolic materials; phonon polaritons; planar subwavelength focusing; tunable focusing
类别
资金
- National Key Research and Development Program of China [2020YFB2205701]
- National Natural Science Foundation of China [51902065, 52172139, 51925203, U2032206, 52072083, 51972072]
- Beijing Municipal Natural Science Foundation [2202062]
- Strategic Priority Research Program of Chinese Academy of Sciences [XDB36000000, XDB30000000]
- ERC [834742]
- Spanish MICINN [PID2020-112625GB-I00, SEV2015-0522]
- CAS President's International Fellowship Initiative (PIFI)
- Academy of Finland [314810, 333982, 336144, 336818]
- Business Finland [320167]
- European Union [820423, 965124]
- EU [H2020-MSCA-RISE-872049]
A tunable planar focusing device operating in the mid-IR region is reported by exploiting highly oriented in-plane hyperbolic phonon polaritons in alpha-MoO3. The device allows for unprecedented control of the effective focal length of polariton waves through the dimension of the device, the employed light frequency, and engineering of phonon-plasmon hybridization.
Manipulation of the propagation and energy-transport characteristics of sub-wavelength infrared (IR) light fields is critical for the application of nanophotonic devices in photocatalysis, biosensing, and thermal management. In this context, metamaterials are useful composite materials, although traditional metal-based structures are constrained by their weak mid-IR response, while their associated capabilities for optical propagation and focusing are limited by the size of attainable artificial optical structures and the poor performance of the available active means of control. Herein, a tunable planar focusing device operating in the mid-IR region is reported by exploiting highly oriented in-plane hyperbolic phonon polaritons in alpha-MoO3. Specifically, an unprecedented change of effective focal length of polariton waves from 0.7 to 7.4 mu m is demonstrated by the following three different means of control: the dimension of the device, the employed light frequency, and engineering of phonon-plasmon hybridization. The high confinement characteristics of phonon polaritons in alpha-MoO3 permit the focal length and focal spot size to be reduced to 1/15 and 1/33 of the incident wavelength, respectively. In particular, the anisotropic phonon polaritons supported in alpha-MoO3 are combined with tunable surface-plasmon polaritons in graphene to realize in situ and dynamical control of the focusing performance, thus paving the way for phonon-polariton-based planar nanophotonic applications.
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