A kind of plasmonic nanostructure is proposed that can generate the arbitrary superposition of orbital angular momentum (OAM) states in surface plasmons (SPs), which is achieved by combining the segmented spirals with nanoslit pairs. The structures can independently modulate both the phase and amplitude of SP waves, and thus enable the superposition of two OAM states with arbitrary topological charges (TCs) as well as free control of their relative amplitudes. Superposed states distributed over the entire Bloch sphere and hybrid superposed states with different TCs were constructed and experimentally demonstrated. This work will offer more opportunities for multifunctional plasmonic devices.
Hybrid organic-inorganic perovskite shows a great potential in the field of photoelectrics. Embedding methyl ammonium lead bromide (MAPbBr3) in a mesoporous silica (mSiO2) layer is an effective method for maintaining optical performance of MAPbBr3 at room temperature. In this work, we synthesized MAPbBr3 quantum dots, embedding them in the mSiO2 layer. The nonlinear optical responses of this composite thin film have been investigated by using the Z-scan technique at a wavelength of 800 nm. The results show plural nonlinear responses in different intensities, corresponding to one- and two-photon processing. Our results support that composites possess saturation intensity of ~27.29 GW/cm2 and varying nonlinear coefficients. The composite thin films show high stability under ultrafast laser irradiating. By employing the composite as a saturable absorber, a passively Q-switching laser has been achieved on a Nd:YVO4 all-solid-state laser platform to generate a laser at ~1 μm.
Metasurfaces with orthogonal nano-slit pairs arranged on spirals are proposed to generate vector beams (VBs) of Bell-like states and slanted polarizations. The design of the metasurfaces is based on the theoretically derived parameter condition for manipulation of the two vector vortex modes, which is satisfied by matching the three parameters of rotation order
m
, the spiral order
n
, and incident polarization helicity
σ
. The linear polarization states of the VBs are controlled by the initial orientation angle
φ
0
of slit pairs. VBs of satisfying quality are experimentally obtained, with the analytical and simulated results validated.
The manipulation of high-quality vector beams (VBs) with metasurfaces is an important topic and has potential for classical and quantum applications. In this paper, we propose a Fresnel zone (FZ) metasurface with metallic nanoslits arranged on FZs, which sets alternate binary geometric and propagation phases to cancel the incident spin component and focus the converted spin component (CSC). The rotation designs of nanoslits transform the incident polarization state on the conventional Poincaré sphere to VBs on the higher-order Poincaré (HOP) sphere. The two orbital angular momentum states of the CSCs were manipulated, and the focused HOP beams were generated. The experimental results demonstrate the broadband generation of arbitrarily focused HOP beams of high quality under the illumination of the red (632.8 nm), green (532 nm), and blue (473 nm) light. This work will be of significance for the applications of VBs in different areas, such as precision metrology, optical micromanipulation, and quantum information.
The trefoil and cinquefoil vector field are of essential significance for fundamental topology properties as the Hopf link and trefoil knots in the light field. The spatially multiplexing metasurfaces were designed with two sets of periodical nanoslits arranged alternately, each had independent geometric spiral phases and metalens phases to produce and focus vortex of the corresponding circular polarized (CP) light. By arranging the orientations of the two slit sets, the two CP vortices of the desired topological charges were obtained, the superposition of the vortices were realized to generate the vector field. With the topological charges of the vortices set to one and two, and three and two, respectively, the focused trefoil and cinquefoil vector light fields were acquired. The work would be important in broadening the applications of metasurface in areas as vector beam generations and topology of light field.
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