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 ∼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.

Metasurfaces have provided a promising approach to enhance the nonlinearity at subwavelength scale, but usually suffer from a narrow bandwidth as imposed by sharp resonant features. Here, we counterintuitively report a broadband, enhanced second-harmonic generation, in nanopatterned hyperbolic metamaterials. The nanopatterning allows the direct access of the mode with large momentum, rendering the rainbow light trapping, i.e. slow light in a broad frequency, and thus enhancing the local field intensity for boosted nonlinear light-matter interactions. For a proof-of-concept demonstration, we fabricated a nanostructured Au/ZnO multilayer, and enhanced second harmonic generation can be observed within the visible wavelength range (400-650 nm). The enhancement factor is over 50 within the wavelength range of 470-650 nm, and a maximum conversion efficiency of 1.13×10−6 is obtained with a pump power of only 8.80 mW. Our results herein offer an effective and robust approach towards the broadband metasurface-based nonlinear devices for various important technologies.

A dual-resonance all-dielectric metasurface was demonstrated to enhance the signals emitted by upconversion nanoparticles (NaYF4:Yb/Tm).

Compared to natural materials, artificial subwavelength structures can enhance chiroptical effects in a stronger way, and the requirement of low material loss and wideband operation is desired in many situations. Here, we propose an all-dielectric chiral metasurface as a periodic array of centrosymmetric staggered silicon cuboid pairs to achieve strong circular dichroism in a wide band. As a demonstration, the designed chiral metasurface may strongly reflect the chosen circularly polarized light with the spin preserved in the operating wavelength range of 1.51 ∼ 1.60 µm while highly transmit (with an efficiency greater than 95%) the opposite circularly polarized light with the spin flipped. Then, two application cases are given for the designed chiral metasurface. A flat chiral meta-lens is constructed to produce wideband focusing in the transmission/reflection side while the disturbing from the opposite circular polarization is well blocked by high reflection/transmission. A chiral Fabry-Perot cavity is also constructed, which has an extremely high quality factor (2.1E4). The proposed method provides an efficient way to produce strong chiroptical effects and has a promising potential for various applications such as signal processing, sensing, radiation and detection.

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A process using plentiful and inexpensive caustic calcined magnesia (CCM; main component is MgO) to prepare lamellar MH of high purity is described. The process begins with the reaction of MgO in CCM with NH4NO3 at ∼100 °C to produce ammonia gas and Mg(NO3)2 solution and the subsequent filtration of Mg(NO3)2 solution to remove impurities (e.g., SiO2). Then, the obtained ammonia is introduced into the Mg(NO3)2 solution to produce MH precipitate and NH4NO3. After the MH precipitate is separated by filtration, the filtrate containing NH4NO3 is returned to the initial step. The overall reaction of this process is the hydration of MgO to MH. Therefore, this process is called the apparent-hydration method. This apparent-hydration method overcomes the disadvantages of the true hydration method, such as the inability to remove impurities. A crucial finding is that, because of the presence of trace SO4 2– in the obtained Mg(NO3)2 solution, a MH product with a narrow particle size distribution cannot be produced. After removal of the SO4 2– with Ba(NO3)2, lamellar MH with a narrow particle size distribution can be synthesized at 120 °C in one step. This work provides a promising route to the use of CCM to prepare MH.

A facile polymethyl methacrylate-assisted turnover-transfer approach is developed to fabricate uniform hexagonal gold nanobowl arrays. The bare array shows inferior light trapping ability compared to its inverted counterpart (a gold nanospherical shell array). Surprisingly, after being coated with a 60-nm thick amorphous silicon film, an anomalous light trapping enhancement is observed with a significantly enhanced average absorption (82%), while for the inverted nanostructure, the light trapping becomes greatly weakened with an average absorption of only 66%. Systematic experimental and theoretical results show that the main reason for the opposite light trapping behaviors lies in the top amorphous silicon coating, which plays an important role in mediating the excitation of surface plasmon polaritons and the electric field distributions in both nanostructures.

Optical phased arrays occupy the predominant position in the solid-state light detection and ranging; however, their applications are limited by high insertion loss, complex control, and the need for tunable lasers. Here, by assembling a quadratic silicon metalens onto the end face of a single-mode fiber array to form a metafiber, we propose an all-solid-state beam steering module. With the introduction of the flat metalens, the module is highly compact, and the field of view may be extremely wide. A large field of view up to about 60°is testified experimentally based on a one-dimensional module. The application for parking space monitoring is also demonstrated based on a two-dimensional module. The beam steering module can be switched between the scanning mode and the flash mode compatibly and can also be extended to a larger scale with a higher scanning precision by increasing the size of the fiber array and scaling the metalens. The presented scheme featured with high compactness, high performance, and good compatibility provides a distinctive beam steering candidate for light detection and ranging or optical wireless communication applications.