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The bound state in the continuum (BIC) is widely applied to metamaterial study in order to obtain robust resonance and high quality (Q) factor. In this paper, we propose a metallic metasurface structure that can support double types of BICs, and acquire quasi-BIC state by restructuring each type with a specific approach. Electric field distribution is investigated to explore the physic mechanism behind the evolution of BICs. Moreover, we substitute structured graphene with corresponding metal counterparts. The promoted design is able to switch freely between BIC and quasi-BIC state even after the fabrication, as the graphene would convert from semiconductor-like to metal-like when increasing the Fermi level. Further exploration on electric field distribution demonstrates the metallicity difference between graphene and gold, which leads to the exotic phenomenon emerge on the proposed metal-graphene structure. Finally, the proposed metal-graphene structure is applied to a digital coding display through Fermi level regulating. Therefore, our work provides deep insights to the BIC metasurface investigation, and introduces a desirable improvement for current BIC metasurface design to achieve the free conversion between BIC and quasi-BIC states.

Superoscillation is a kind of phenomenon which can generate oscillation faster than the fastest component of a band-limited function. For optics, superoscillation is generated by coherence of low spatial frequency waves. It can bring a localized region named “hot spot”, which has a smaller size than the diffraction-limit, and this character has potential applicaions in super-resolution imaging. Using a high-order radially polarized Laguerre-Gaussian beam tightly focused by high-NA objective lens, we can easily obtain and control the superoscillation hot spot. Using a metasurface, which has compact volume and sub-wavelength pixel size, we can generate the high-order radially polarized Laguerre-Gaussian beam more simply than conventional methods like using a liquid crystal mode converter. We first analyze the properties of unit cells of the metasurface and simulate the performance of the metasurface. Then we analyze the property of the tightly focused high-order radially polarized Laguerre-Gaussian beam and design a super-resolution imaging system using our designed metasurface. Therefore, the 2-fold lateral resolution enhancement is realized in our approach. This method can be used to improve lateral resolution in conventional confocal imaging systems.

Erratum to “Creating perfect composite vortex beams with a single all-dielectric geometric metasurface.” [Opt. Express 30, 40231 (2022)10.1364/OE.475158]. Here are some mistakes in the paper, which needs to be revised.

Vortex beams are playing an increasingly crucial role in wireless optical communications. Traditional vortex beam generators based on spiral phase plates and metasurfaces have a geometric center in real space, which limit their convenience in practical applications. In this work, we propose that the creation of a vortex beam can be achieved by using the bound state in the continuum (BIC) supported by a photonic crystal slab structure. Theoretical analysis shows that the proposed structure can be used as a kind of “momentum-space resonators” and thus can generate vortex beams. Moreover, higher-order vortex beams can also be achieved by changing the symmetry of photonic crystal slab, thus paving the way for the application of vortex beams in the fields of quantum information processing and micro optical micromanipulation.

Optical vortex beam carrying orbit angular momentum has been extensively researched and applied recently. Among which a perfect vortex beam (PVB) has attracted much attention owing to its topological charge (TC)-irrelevant intensity profile. However, the morphology singularity, as well as implementation complexity of the PVB tie the degree of freedom for multiplexing. Herein, by introducing the concept of a composite vortex beam, we originally propose a novel kind of PVB – perfect composite vortex beam (PCVB) – which possesses a rosette-like intensity pattern that is exactly correlated with the TC and can be directly generated using a single all-dielectric geometric metasurface rather than bulky optical systems. We numerically simulate the broadband generation of the proposed PCVB with various TCs, sizes, and rotation angles. To further explore the potential of our design in practical applications, we demonstrated the coaxial array of the PCVBs and detected their optical angular force for manipulating nanoparticles. We believe that our fruitage may pave a desirable avenue for optical communication, information processing, and optical manipulation.

Quantum coherence has been considered as a resource for quantum information process in recent years. Sharing the quantum resource distantly is a precondition for quantum communication. In this paper, we explore the quantum coherence properties of the prepared state starting from initially incoherent thermal light source. It is shown that the quantum coherence is directly proportional to the dimension of Hilbert space and therefore employ the orbital angular momentum (OAM) to encode resources. The distribution of biphoton thermal OAM state via the one-sided noisy channel (non-Kolmogorov turbulent atmosphere) is then investigated. It is found that the prepared OAM state can have large amount of quantum coherence, which is maximized when the thermal source is completely incoherent. The turbulence effects on quantum coherence are studied and compared to those on the fidelity and quantum channel capacity. Contrasting to the monotonic decay, the dynamics of coherence displays a peak during the propagation and the mechanism behind is presented. Finally, the dynamics of quantum thermal state can be more robust than that of Bell-like pure state since more interference can be induced. We believe our results is of importance to OAM quantum communication using quantum coherence as a resource.

A device incorporating a series of periscope-like waveguides to achieve bidirectional focusing and plasmon launching is proposed. Optimizing the number, positions, and dimensions of the waveguides and tuning the waveguide optical paths both produce the required phase shifts to shape wavefronts and achieve constructive interference at the desired points. Due to the symmetry and reversibility of the structure, the lens can focus the light incident on both sides. Energy redistribution to a specific multi-focus can also be achieved by applying appropriate phase shifts. This simple and high performance structure makes the bidirectional plasmonic launcher easy to implement in various application situations.

A new multiple-image optical encryption scheme based on phase retrieval algorithm and fractional Talbot effect is proposed. In encryption process, by using Fresnel domain phase retrieval algorithm, each image is encoded into a pure phase distribution with different spatial constraints. The spatial constraints are chosen as complementary square aperture array. A Talbot illuminator is designed according to the fractional Talbot effect, which is treated as a decoder to obtain the designed square aperture array. Then all obtained phase distributions are combined into the final ciphertext image. In decryption process, the images can be decoded from the ciphertext by using the Talbot illuminator and keys. Benefit from the use of fractional Talbot effect, the demultiplexing setup of the cryptosystem is very simple and straightforward, with no need of lens. The simulation results prove that the multiplexing capability is considerably enhanced. At the same time, the security analysis proves that the system can resist various attacks.

Halogen perovskites have high refractive indexes and adjustable bandgaps, making them promising materials for all-dielectric and tunable metasurfaces. Herein, we design tunable polarization-converted halogen-perovskite metasurfaces and explained their characteristics in theory by using the Jones matrix. We propose a halogen-perovskite color holographic metasurface with low crosstalk owing to the excellent monochromatic permeability of three halogen perovskites (MAPbCl3: 450 nm; MAPbBr3: 550 nm; MAPbI3: 740 nm). In addition, we build three independent imaging channels to prevent color crosstalk between them to achieve fantastic imaging applications. This study serves as a good reference for research on optical information storage, polarization optics, holographic image encryption.

Because of the low temporal resolution, it is difficult to imaging a moving object using single-pixel imaging. In previous studies, either the frame rate is limited, or the speed and direction is limited to constant. In this work, a fast tracking and imaging method for moving objects is proposed. By using cake-cutting order Hadamard illumination patterns and the TVAL3 algorithm, low-resolution images of each frame are obtained. The displacement is calculated via the cross-correlation between the low-resolution images, and the illumination patterns are modified according to the location results. Finally, a high-quality object image is obtained. This scheme is suitable for moving object imaging with varying speeds and directions. The simulation and experimental results prove that for a 128 × 128 pixels scene, the location and imaging can be realized when 30 samplings are performed for each time interval. We experimentally demonstrate that the proposed method can image a moving object with variational speed with a resolution of 128 × 128 pixels at a frame rate of 150 fps by using a 9 kHz digital micromirror device. The proposed scheme can be used for three-dimensional and long-distance moving object imaging.

In this paper, we propose a tunable, multi-band, selective absorber composed of multiple layers. Each layer consisted of SiO2/graphene/SiC, and a layer of silver was used as the ground plane of the entire structure. Simulation results show that we can passively and actively coordinate the resonant frequency of the perfect absorption peak by changing the geometric parameters of the array and the Fermi level of the graphene. The absorber is not sensitive to the angle of incidence and the direction of polarization. We propose a theoretical basis for the formation of multiple absorption peaks. The theoretical calculations are in good agreement with the simulation results. In addition, we simulated the three- and four-layer structures. The results show that in the terahertz (THz) band, composite structures of three and four layers can obtain three and four perfect absorption peaks, respectively. Our results provide new insights into the THz band of harmonizable multi-band absorbers that can be applied to THz imaging to coordinate sensors and other optoelectronic devices.

We investigate the dynamics of quantum coherence and quantum correlation of two qubits mediated by a one-dimensional plasmonic waveguide. The analytical expression of the dissipative dynamics of the two qubits is obtained for the initial X state. The dynamical behaviors of the quantum coherence and quantum correlation are shown to be largely dependent on the parameters of the initial state. Starting from a product state, quantum coherence and quantum correlation can be induced by the plasmonic waveguide. Under continuous drivings, steady quantum correlation can be obtained at specific distance larger than the operating wavelength and large values of steady quantum coherence are attainable at arbitrary distance. The detuning effect on the dissipation-driven generation of steady quantum coherence and quantum correlation is also explored.

We study the plasmonic properties of face-to-face phosphorene pairs, including their optical constraints and optical gradient forces. The symmetric and anti-symmetric plasmonic modes occur due to the strong anisotropic dispersion of phosphorene. Compared with the anti-symmetric mode, the symmetric mode has a stronger optical constraint and much larger gradient force. Especially, the optical constraint of the symmetric mode can even reach as high as 96% when the two phosphorene layers are along the armchair and zigzag direction respectively. We also propose a scheme of an ultra-small phase shifter using phosphorene-based photonic devices.

A grating-coupled Otto configuration consisting of multilayer films including a few layers of graphene and a germanium prism is proposed. A sharp and sensitive Fano resonance appears when a graphene surface plasmon polaritons (GSPPs) mode from the graphene-dielectric interface couple with the planar waveguide (PWG) mode. We utilize the classical harmonic oscillator (CHO) to explain Fano resonance and study the influence of various parameters of the configuration on the reflection spectra. The highly sensitive sensor can be achieved by introducing detected materials into Otto structure. In addition, we investigated the effects from material loss arising in our designs. All of the simulations are performed by a finite element method (FEM).

We report a new optical technique to map two-dimensional temperature distributions in liquid solutions based on the thermal motion of fluorescent molecules. We simultaneously capture the fluorescence images of different numerical apertures (NAs) to resolve the temperature-dependent orientations of emission dipoles. In this work, we use two numerical apertures (2NA) prove the concept. This 2NA technique is robust against the intensity variations caused by photobleaching, unsteady illumination and nonuniform molecule distribution. Moreover, as the measured intensity of directional emission is insensitive to polarization changes, this method can be applied to polarizing materials, such as metal surfaces. Under this configuration, the 2NA technique offers another advantage of naturally filtering out the emission background that falls out of collection cones. We foresee the 2NA technique to open a new detection scheme of fluorescence thermometry.