We present electrically-driven generation and dynamics of the real-space optical vortices based on the high-dimensional gradient-thickness optical cavity. The structure consists of a metal-dielectric multi-layer that supports non-trivial topological phases, generating optical vortex lines and rings in three-dimensional generalized parameter space. We experimentally demonstrated the high-dimensional gradient-thickness optical cavity by liquid crystal-based multi-layer structure, which bijectively projects a surface slice of generalized parameter space into the real space. By electric control of the alignment of liquid crystal molecules, we successfully spanned the architecture of the high-dimensional optical singularity in real space, which actively generates and manipulates the optical vortex-antivortex pair.
Owing to the Purcell effect, optical micro-structures can control the radiative decay of the quantum emitters in transition metal dichalcogenide (TMDC) media. However, conventional optical microstructures change the local density of optical states (LDOS) not only at the photoluminescence (PL) wavelength of the TMDC quantum emitters and but also at the pump wavelength simultaneously and thus cause an inevitable influence on the excitation conditions. We propose and experimentally demonstrate a reflective metallic metasurface for independently engineering the excitation and radiation of quantum emitters in the TMDC monolayer
We present a sub-wavelength-scale plasmomechanical system consisting of an Au/hydrogen silsesquioxane (HSQ) plasmonic nano-resonator and a supporting HSQ nano-wall. The full footprint of the system in three dimensions is only ~0.15 μm^3, which is just ~0.59 times of cubic wavelength. Strong optical scattering and dissipation of plasmonic resonance enable interaction with mechanical motion. We experimentally demonstrate the optical excitation and readout of the fundamental longitudinal mechanical oscillation, of which the real displacement is in the order of pico-meter. The plasmonic resonance with a wide spectral width allows the optical measurement of the mechanical oscillation signal over a large wavelength range (>100 nm) of the probe laser. Our dissipatively coupled plasmomechanical system shows not only tunability of the resonance frequency of mechanical oscillation but also the thermoelastic damping effect on the mechanical quality factor depending on the pump laser power.
The interlayer exciton of van der Waals heterostructure has become a promising platform for realizing Bose-Einstein condensation and demonstrating novel excitonic devices. For increasing the critical temperature of bosonic condensation or long-range transport, the short lifetime of the interlayer excitons has to be improved by suppressing both the radiative and non-radiative recombination processes[1,2]. However, due to its out-of-plane electric dipole nature, the radiative recombination of the interlayer exciton has not yet been able to be suppressed with conventional optical approaches[3,4]. Here, we present a theoretical study on the reflective metasurface that can suppress the density of optical states for the out-of-plane dipole moment. The metasurface consists of Au nanodisks arranged in a square lattice on the Au substrate. We examined the out-of-plane dipole emitter inside the 20-nm-thick hexagonal-BN layer, which is placed on the flat surface of the 140-nm-thick SiO2 layer covering the Au disk array. We targeted the WSe2/MoSe2 interlayer exciton of which the radiation wavelength is 900 nm. Blocking the radiative decay channels of the dipole emitter to the horizontal directions as well as the vertical directions, the proposed metasurface strongly suppresses the Purcell factor down to ~0.011 at maximum (~0.018 on average), which corresponds to the enhancement of the radiative decay time as amount as ~91 times (~56 times).
We investigated resonant light scattering properties of single wavelength-scale metallic or dielectric nanorods in the energy-momentum space. High-refractive-index silicon nanostructures supporting strong Mie resonances allow light manipulation beyond the optical diffraction limit. Based on dark-field microscopy and numerical modal analysis, we revealed that the waveguide dispersion of the silicon nanorod determines and controls the resonant scattering properties. We also demonstrated for the first time quantitative measurement of the differential far-field scattering cross-section of a single metal nanostructure over the full hemisphere. While conventional back-focal-plane imaging suffers from optical aberration/distortion and numerical aperture limit of the objective lens, goniometer-based direct solid angle scanning provides quantitative and flawless information of far-field scattering from nanostructures on the wavelength scale or less.
We propose and demonstrate a metal-dielectric thin film that delivers low reflection and high absorption over the entire
visible spectrum. This thin black film consists of SiO2/Cr/SiO2/Al layers deposited on glass substrate. Measured
reflectance and absorptance of the black film are 0.7% and 99.3%, respectively, when averaged over the range 380-780
nm. The total thickness of the black film is only about 220 nm. This thin black film can be used as a thin absorbing layer
for displays that require both broadband anti-reflection and high contrast characteristics.
Lasing dynamics of photonic-crystal single-cell cavity is studied by Lorentz-dispersive Gain FDTD method. From hexapole mode of a photonic-crystal single-cell cavity, the generation of laser modes and the relaxation oscillation are observed.
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