Search

Strong coupling between emitters and cavities underlies many of the current strategies aiming at generating and controlling quantum states at room temperature. Recent experiments reveal strong coupling between two-dimensional transition metal dichalcogenides (TMDCs) and individual plasmonic structures; however, the coupling strength is quite limited (<200 meV), and the active control of the coupling strength is challenging. Here, we demonstrate the active tuning of plexcitonic coupling in monolayer WS 2 coupled to a plasmonic nanocavity by immersing into a mixed solution of dichloromethane (DCM) and ethanol. By adjusting the mixture ratio, continuous tuning of the Rabi splitting energy ranged from 183 meV (in ethanol) to 273 meV (in DCM) is achieved. The results are mainly attributed to the remarkable increase of the neutral exciton density in monolayer WS 2 as the concentration of DCM is increased. It offers an important stepping stone toward a further study on plexcitonic coupling in layered materials, along with potential applications in quantum information processing and nonlinear optical materials.

Hybrid organic-inorganic perovskites have emerged as promising thermoelectric materials due to their attractive figure of merits. To further reduce their thermal conductances ( G ) and improve the thermoelectric efficiencies, fabrication of phononic crystals (PnCs) could be an effective approach. In this work, CH 3 NH 3 PbI 3 -based PnCs were developed and their thermal transports were engineered by optimizing the configurations of both basal bodies and scatterers. Our cross-scale simulations demonstrate that low relative G can be achieved in CH 3 NH 3 PbI 3 PnCs with large scatterers but low-symmetric PnC lattices, basal bodies, and scatterers. Moreover, we discovered the increased disorder of CH 3 NH 3 + cations from tetragonal to cubic transition significantly increases the phonon velocities and reverses the phonon transport from diffusive to quasi-ballistic, leading to an abnormal reduction of relative G . This work provides a new pathway for engineering thermal conductivity of hybrid perovskites and improving the performance of corresponding devices.

Here we study the Jahn-Teller (JT) effect on framework flexibility of two analogous hybrid organic-inorganic perovskites, [C(NH 2 ) 3 ][Zn(HCOO) 3 ] (1-Zn) and [C(NH 2 ) 3 ][Cu(HCOO) 3 ] (2-Cu). Single-crystal nanoindentation measurements show that the elastic moduli and hardnesses of 1-Zn are up to ∼52.0% and ∼25.0% greater than those of the JT active 2-Cu. Temperature-dependent X-ray diffraction measurements indicate that the thermal expansion along the b-axis is switched from negative to positive by replacing Zn 2+ with Cu 2+ on the B-site. These stark distinctions in framework flexibility are primarily attributed to the ∼10.0% elongation of Cu-O bonds induced by the JT effect and associated alterations in octahedral tilting and hydrogen-bonding. Our results demonstrate the prominence of the JT effect in the emerging hybrid perovskites and highlight the possibilities of tuning materials' properties using orbital order.

Recently, nonlinear hybrid metasurface comes into an attractive new concept in the research of nanophotonics and nanotechnology. It is composed of semiconductors with an intrinsically large nonlinear susceptibility and traditional plasmonic metasurfaces, offering opportunities for efficiently generating and manipulating nonlinear optical responses. A high second-harmonic generation (SHG) conversion efficiency has been demonstrated in the mid-infrared region by using multiquantum-well (MQW)-based plasmonic metasurfaces. However, it has yet to be demonstrated in the visible region. Here, we present a new type of nonlinear hybrid metasurfaces for the visible region, which consists of a single layer of tungsten disulfide (WS 2 ) and a phased gold nanohole array. The results indicate that a large SHG susceptibility of ∼10 -1 nm/V at 810 nm is achieved, which is 2-3 orders of magnitude larger than that of typical plasmonic metasurfaces. Nonlinear metalenses with the focal lengths of 30, 50, and 100 μm are demonstrated experimentally, providing a direct evidence for both generating and manipulating SH signals based on the nonlinear hybrid metasurfaces. It shows great potential applications in designing of integrated, ultrathin, compacted, and efficient nonlinear optical devices, such as frequency converters, nonlinear holography, and the generation of nonlinear optical vortex beams.

We report on the systematical study of the second-harmonic generation (SHG) in single zinc sulfide nanowires (ZnS NWs). The high-quality ZnS NWs with round cross-section were fabricated by chemical vapor deposition method. The transmission electron microscopy images show that the actual growth axis has a deviation angle of 0°∼20° with the preferential growth direction [120], which leads to the various polarization-dependent SHG response patterns in different individual ZnS NWs. The SHG response is quite sensitive to the orientations of c axis as well as the (100) and (010) crystal-axis of ZnS NWs; thus, all the three crystal-axis orientations of ZnS NWs are precisely determined by the SHG method. A high SHG conversion efficiency of 7 × 10(-6) is obtained in single ZnS NWs, which shows potential applications in nanoscale ultraviolet light source, nonlinear optical microscopy, and nanophotonic devices.

We report a direct observation on the laterally emitted surface second harmonic generation (SHG) in a single ZnTe nanowire. The highly directional surface SHG radiates vertically to the nanowire growth-axis with a high conversion efficiency of 5 × 10(-6) and a low divergence angle of 4°. Polarization state, emission intensity, and direction of the surface SHG are found to be dependent on the polarization of the pumping laser, which is further confirmed by numerical simulations. The laterally emitted surface SHG with a high efficiency and low divergence angle has great potential for short-wavelength nanolasers, nonlinear microscopic imaging, and polarization-dependent photonic integrating.

Highly flexible, robust, and sensitive infrared nanosensors were fabricated based on carbon nanoparticles that were synthesized through a simple and low-cost flame method. The infrared nanosensor devices showed sharp infrared photoresponse with a response time of ∼68 ms and a maximum photocurrent change of ∼52.9%. The devices showed a superhydrophobic property with a contact angle larger than 150° and a sliding angle of ∼4°. The mechanism for the enhanced infrared photoresponse from carbon nanoparticles is discussed.