| 1. |
- Bao, Fanglin, et al.
(författare)
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Inhomogeneity-Induced Casimir Transport of Nanoparticles
- 2018
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 121:13
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Tidskriftsartikel (refereegranskat)abstract
- We propose a scheme for transporting nanoparticles immersed in a fluid, relying on quantum vacuum fluctuations. The mechanism lies in the inhomogeneity-induced lateral Casimir force between a nanoparticle and a gradient metasurface and the relaxation of the conventional Dzyaloshinskii-Lifshitz-Pitaevskii constraint, which allows quantum levitation for a broader class of material configurations. The velocity for a nanosphere levitated above a grating is calculated and can be up to a few microns per minute. The Born approximation gives general expressions for the Casimir energy which reveal size-selective transport. For any given metasurface, a certain particle-metasurface separation exists where the transport velocity peaks, forming a "Casimir passage." The sign and strength of the Casimir interactions can be tuned by the shapes of liquid-air menisci, potentially allowing real-time control of an otherwise passive force, and enabling interesting on-off or directional switching of the transport process.
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| 2. |
- Shi, Kezhang, et al.
(författare)
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Colossal Enhancement of Near-Field Thermal Radiation Across Hundreds of Nanometers between Millimeter-Scale Plates through Surface Plasmon and Phonon Polaritons Coupling
- 2019
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Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 19:11, s. 8082-8088
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Tidskriftsartikel (refereegranskat)abstract
- Coupling modes between surface plasmon polaritons (SPPs) and surface phonon polaritons (SPhPs) play a vital role in enhancing near-field thermal radiation but are relatively unexplored, and no experimental result is available. Here, we consider the NFTR enhancement between two identical graphene-covered SiO2 heterostructures with millimeter-scale surface area and report an experimentally record-breaking, similar to 64-fold enhancement compared to blackbody (BB) limit at a gap distance of 170 nm. The energy transmission coefficient and radiation spectra show that the physical mechanism behind the colossal enhancement is the coupling between the surface plasmon and phonon polaritons.
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| 3. |
- Shi, Kezhang, et al.
(författare)
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Enhanced Near-Field Thermal Radiation Based on Multilayer Graphene-hBN Heterostructures
- 2017
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Ingår i: ACS Photonics. - : AMER CHEMICAL SOC. - 2330-4022. ; 4:4, s. 971-978
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Tidskriftsartikel (refereegranskat)abstract
- Graphene-covered hexagonal boron nitride (hBN) can exceed blackbody thermal radiation in near-field due to the coupling of surface plasmon polaritons (SPPs) and hyperbolic phonon polaritons (HPPs). As previous research found that the thickness of hBN in a graphene-hBN cell can be very thin while still presenting strong radiation enhancement, multilayer graphene-hBN heterostructures are proposed in this paper to further enhance the near-field thermal radiation. We found that a heterostructure consisting of five or more graphene-hBN cells performs better than all existing graphene-hBN configurations, and the infinite cell limit exhibits 1.87- and 2.94-fold larger heat flux at 10 nm separation than sandwich and monocell structures do, respectively, due to the continuously and perfectly coupled modes. The heat flux is found to be 4 orders of magnitude larger than that of the blackbody. The effective tunability of the thermal radiation of the multicell structure is also observed by adjusting the chemical potentials of graphene with an optimized thickness of 20 nm on each hBN, which is instructive for both experimental design and fabrication of thermal radiation devices.
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| 4. |
- Shi, Kezhang, et al.
(författare)
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Enhancing thermal radiation by graphene-assisted hBN/SiO2 hybrid structures at the nanoscale
- 2018
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Ingår i: Optics Express. - : OPTICAL SOC AMER. - 1094-4087. ; 26:10, s. A591-A601
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Tidskriftsartikel (refereegranskat)abstract
- A graphene-assisted hBN/SiO2, hybrid structure is proposed and demonstrated to enhance near-field thermal radiation (NFTR). Due to the complementarity between the hyperbolic phonon polaritons of hBN and the surface phonon polaritons of SiO2, at mid-infrared frequencies, coupling modes can remarkably improve the photon tunneling probability over a broad frequency band, especially when assisted by the surface plasmon polaritons of graphene sheets. Thus, the heat flux can exceed the blackbody limit by 4 orders of magnitude at a separation distance of 10 nm and reach 97% of the infinite limit of graphene-hBN multilayers using only two layers with a thickness of 20 nm each. The first graphene layer controls most of the heat flux, while the other layers can be used to regulate and optimize. The dynamic relationship between the chemical potential mu and the gap distance d are thoroughly discussed. Optimal heat flux of our graphene-assisted hBN/SiO2 hybrid structure with proper choices of (mu(1), mu(2), mu(3)) for different d (from 10 nm to 1000 nm) is further increased by 28.2% on average in comparison with the existing graphene-hBN triple-layer structure.
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| 5. |
- Shi, Kezhang, et al.
(författare)
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Spectral Control of Near-Field Thermal Radiation With Periodic Cross Resonance Metasurfaces
- 2018
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Ingår i: IEEE Journal of Quantum Electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9197 .- 1558-1713. ; 54:1
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Tidskriftsartikel (refereegranskat)abstract
- Near-field thermal spectra can be engineered using periodic cross resonance metasurfaces. Structures consisting of single crosses, double crosses, and multiple crosses are proposed to control the spectral heat flux from narrow band to broadband with the Fabry-Perot-cavity-like effect and the interaction between the emitter and receiver. Radiation peaks originating from the cross structures split into two adjacent peaks in the near-field, due to the separate contributions of s- and p-polariton modes. Their frequency can be manipulated by adjusting the length of the crosses. Multiple radiation peaks can be generated by double crosses, and due to the strong coupling of resonance modes, multiple crosses can yield a broadband thermal spectrum ranging from 100-180 THz, with the total heat flux two orders of magnitude above the blackbody limit. The inherent physical mechanisms are illustrated by analyzing the energy transmission coefficients of the cross structures. The features of the radiation peaks and spectra are robust to the change of the gap distance or the temperature, which is advantageous for both the experimental design and fabrication of thermal radiation devices.
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| 6. |
- Sun, Yuwei, et al.
(författare)
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Enhancing Circularly Polarized Emission by a Planar Chiral Dielectric Metasurface
- 2023
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Ingår i: Advanced Optical Materials. - : Wiley. - 2162-7568 .- 2195-1071. ; 11:14
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Tidskriftsartikel (refereegranskat)abstract
- Circularly polarized emission (CPE) has attracted great interest in optoelectronics, biosensing, etc. Here, a resonant planar chiral dielectric metasurface that can be constructed to provide a preferable way for CPE is demonstrated. The planar metasurface is easy to fabricate, and the corresponding far-field circular polarization degree is extremely high and angle-insensitive. The designed metasurface is made of a periodic array of in-plane mirror-asymmetric silicon pillar dimers and supports a low-leakage chiral band-edge mode. Experimentally, the photoluminescence of a thin film of PbS/CdS quantum dots coated on such a metasurface is enhanced by 57 times with the far-field degree of circular polarization as high as 0.74. The planar platform provides a flexible and efficient way for manipulating CPE, in which other periodic coupling effects may also be adopted to enhance the light–matter interaction, such as quasi-bound states in the continuum and lattice resonance.
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| 7. |
- Zheng, Jiapeng, et al.
(författare)
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Hybrid optofluidics and three-dimensional manipulation based on hybrid photothermal waveguides
- 2018
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Ingår i: NPG Asia Materials. - : Nature Publishing Group. - 1884-4049 .- 1884-4057. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Despite enormous breakthroughs in lab-on-a-chip techniques, light-driven manipulation faces two long-standing challenges: the ability to achieve both multiform manipulation and tunable manipulation range and the means to avoid potential thermal damage to the targets. By harnessing the optical heating of hybrid photothermal waveguides (HPW), we develop a hybrid optofluidic technique involving buoyancy and thermocapillary convection to achieve fluid transport with controllable modes and tunable strength. Switching of the optofluidic mode from buoyancy to thermocapillary convection, namely, from vertical to horizontal vortices, is employed for three-dimensional manipulation. The strong confinement and torque in the vortices are capable of trapping and rotating/spinning particles at the vortex centers rather than the HPW. Buoyancy convection provides a trapping circle to achieve collective trapping and vertical rotation/spin, while thermocapillary convection offers a trapping lattice to achieve distributed trapping and horizontal rotation/spin. By integrating micro/nanoparticles with various properties and sizes, further investigations of the optofluidic arrangement, mixing, and synthesis will broaden the potential applications of the hybrid optofluidic technique in the fields of lab-on-a-chip, materials science, chemical synthesis and analysis, photonics, and nanoscience.
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