Ghost hyperbolic surface polaritons in bulk anisotropic crystals

Ma, Weiliang; Hu, Guangwei; Hu, Debo; Chen, Runkun; Sun, Tao; Zhang, Chi; Dai, Qing; Zeng, Ying; Alù, Andrea; Qiu, Cheng‐Wei; Li, Peining

doi:10.1038/s41586-021-03755-1

Cited by 130 publications

(105 citation statements)

References 38 publications

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“…In this section, we show that the CNN is capable of quantifying polaritonic oscillations with multiple wavelengths that are simultaneously present in the same field of view of nano-IR images. For example, complex profiles of near-field amplitude composed of multiple waveguide modes are commonly observed in hyperbolic vdW materials. ,,− When the thickness of the crystal is relatively large, the air mode and multiple waveguide modes can be simultaneously excited and probed by s-SNOM. , However, the analysis toolset suitable for processing the multiwavelength data are limited. Fourier transformation (FT) is widely applied to separate multiple modes in momentum space, ,,− but its accuracy suffers when the polaritonic data are impacted by losses with only a few fringes seen in raw images.…”

Section: Resultsmentioning

confidence: 99%

Deep Learning Analysis of Polaritonic Wave Images

McLeod

Chen

et al. 2021

ACS Nano

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Deep learning (DL) is an emerging analysis tool across the sciences and engineering. Encouraged by the successes of DL in revealing quantitative trends in massive imaging data, we applied this approach to nanoscale deeply subdiffractional images of propagating polaritonic waves in complex materials. Utilizing the convolutional neural network (CNN), we developed a practical protocol for the rapid regression of images that quantifies the wavelength and the quality factor of polaritonic waves. Using simulated near-field images as training data, the CNN can be made to simultaneously extract polaritonic characteristics and material parameters in a time scale that is at least 3 orders of magnitude faster than common fitting/processing procedures. The CNN-based analysis was validated by examining the experimental near-field images of charge-transfer plasmon polaritons at graphene/α-RuCl3 interfaces. Our work provides a general framework for extracting quantitative information from images generated with a variety of scanning probe methods.

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Section: Resultsmentioning

confidence: 99%

Deep Learning Analysis of Polaritonic Wave Images

McLeod

Chen

et al. 2021

ACS Nano

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“…The interplay between grating diffraction and material anisotropy enables unprecedented opportunities for directional, bidirectional, and unidirectional excitation and steering of ultraconfined polariton waves. The concept can be readily extended to other frequency ranges and other anisotropic materials (6,9,(29)(30)(31). We foresee that, beyond the grating orientation angle, other parameters (or degrees of freedom), including incident angle (32), polarization, and grating geometric structures, may be used to further control the polariton diffraction.…”

Section: Discussionmentioning

confidence: 99%

Unidirectionally excited phonon polaritons in high-symmetry orthorhombic crystals

Zhang

et al. 2022

Sci. Adv.

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Advanced control over the excitation of ultraconfined polaritons—hybrid light and matter waves—empowers unique opportunities for many nanophotonic functionalities, e.g., on-chip circuits, quantum information processing, and controlling thermal radiation. Recent work has shown that highly asymmetric polaritons are directly governed by asymmetries in crystal structures. Here, we experimentally demonstrate extremely asymmetric and unidirectional phonon polariton (PhP) excitation via directly patterning high-symmetry orthorhombic van der Waals (vdW) crystal α-MoO 3 . This phenomenon results from symmetry breaking of momentum matching in polaritonic diffraction in vdW materials. We show that the propagation of PhPs can be versatile and robustly tailored via structural engineering, while PhPs in low-symmetry (e.g., monoclinic and triclinic) crystals are largely restricted by their naturally occurring permittivities. Our work synergizes grating diffraction phenomena with the extreme anisotropy of high-symmetry vdW materials, enabling unexpected control of infrared polaritons along different pathways and opening opportunities for applications ranging from on-chip photonics to directional heat dissipation.

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“…It is noted that in the current study, as a demonstration of principle, we only employ the simplest form of patterns, and only demonstrate with one type of material. In fact, patterns can be chosen depending on desirable applications, and also materials as long as supporting HPhPs in the THz and LWIR regimes 7,68 . The tuner allows us to modulate the wavefront of the incident light and control their power flow in an engineered space 22−29 , which therefore enables a variety of interesting applications, such as negative refraction, beam steering, holography, metalens, polarization conversion, and among others, in visible and near-infrared ranges to be expanded into the THz and LWIR spectral regimes.…”

Section: Conclusion and Prospectsmentioning

confidence: 99%

In-plane hyperbolic polariton tuners in terahertz and long-wave infrared regimes

Huang

Folland

Sun

et al. 2022

Preprint

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Development of terahertz (THz) and long-wave infrared (LWIR) technologies is mainly bottlenecked by the limited intrinsic response of traditional materials. Hyperbolic phonon polaritons (HPhPs) of van der Waals semiconductors couple strongly with THz and LWIR radiation. However, the mismatch of photon−polariton momentum makes far-field excitation of HPhPs challenging. Here, we propose an In-Plane Hyperbolic Polariton Tuner and demonstrate a first device responding to direct far-field excitation and giving rise to a unique set of characteristic functions at far-field. Such a device is based on patterned surface directly written on van der Waals semiconductors; here α-MoO3. The resonances are found to strongly rely on in-plane hyperbolic polariton of patterned α-MoO3, exhibiting high quality factors up to 300, and to determine the characteristics of resultant tunable polarization and selection of the wavelength of reflection and transmission and regulation of output intensity. This is important to development of THz and LWIR miniaturized devices.

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Ghost hyperbolic surface polaritons in bulk anisotropic crystals

Cited by 130 publications

References 38 publications

Deep Learning Analysis of Polaritonic Wave Images

Deep Learning Analysis of Polaritonic Wave Images

Unidirectionally excited phonon polaritons in high-symmetry orthorhombic crystals

In-plane hyperbolic polariton tuners in terahertz and long-wave infrared regimes

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