JNP thanks the reviewers who served the journal in 2022.

Optical perfect absorbers have attracted much attention due to their wide applications in areas including optical sensors, energy utilization, and photocatalysis. We present the design, characterization, and experimental demonstration of a narrowband, polarization- and angular-insensitive, high-performance plasmonic metasurface absorber in near-ultraviolet region. A measured absorption peak of 89% is achieved at the wavelength of ∼380 nm, though the calculated results give near-perfect absorption at the resonance wavelength. Our findings will promote more research on metasurface absorbers in near-ultraviolet region.

The ability to modify and shape the surface of polymer and composite materials is crucial for a number of biological and electronics applications. Molybdenum disulfide (MoS₂) and graphene are two-dimensional materials that have distinctive electrical and optical properties that are useful in many optoelectronic applications. The latest applications of graphene / MoS₂, as well as heterostructure manufacturing, properties, and applications, are discussed. Heterostructured materials, as opposed to single-component materials, are designed to provide additional functionality or flexibility. Our study focuses on their unique traits and capabilities, as well as applications, notably in the field of photodetector technology.

In search of next-generation optical information functional materials, magneto-optical microstructures have attracted great attention since they can break Kirchhoff’s law and produce higher photoelectric conversion efficiency. Theoretical studies using finite-difference time-domain and transfer matrix methods have been performed to investigate the optical properties of magneto-optical microstructures. However, these methods are computationally intensive and require periodic conditions, which may not be satisfied with most fabricated samples. The equivalent medium algorithm is improved to make it suitable for the equivalent of magneto-optical materials. Based on the improved equivalent medium theory (EMT), a magneto-optical InSb film structure doped with Au particles (D-InSb) is designed. The effective dielectric functions of the D-InSb layer for transfer matrix waves are obtained from the Bruggeman approximation. Thin-film optics formulas incorporating the anisotropic wave propagation in uniaxial media are employed to calculate the nonreciprocal absorptance of the D-InSb film. The effect of geometric parameters, such as filling ratio and number of layers, is investigated. In addition to modeling the directional radiative properties at various angles of incidence, the hemispherical properties are also calculated to understand the light absorption. The results of our study can provide methods and ideas for the design of solar cells, infrared absorbers, and optical isolators.

A two-dimensional (2D) simple structured ultranarrow-band metamaterial perfect absorber (MPA) with nanocylindrical array is studied both theoretically and experimentally. Using a dielectric 2D cylindrical array as the top grating layer of the MPA, an ultranarrow nonpolarizing absorption peak at normal incidence is obtained. Furthermore, we use the same dielectric material to simplify the topology of the ultranarrow-band MPA, and the number of film layers in the MPA is reduced from 3 to 1. By optimizing its structural parameters and metal substrate, the highest ultranarrow nonpolarizing absorption peak that approaches 1 at normal incidence is obtained. To analyze the absorption physical mechanism, the heat power density distributions of the optimized MPA are simulated to see where the incident light is absorbed. Moreover, numerical simulation results show that the main transverse-electric absorption peak of the optimized MPA is insensitive to the incident angle, and the main transverse magnetic absorption peak is sensitive to the incident angle. Finally, we fabricate an MPA sample with dielectric nanocylindrical array and measure its absorption spectra to make a further comparison. The experimental data are consistent with the theoretical ones. This method might be helpful to reduce the manufacture difficulty and cost of the ultranarrow-band MPAs and also to promote the development of applications of the ultranarrow-band MPAs.

A yolk-shell structure is a double-layer hollow nanostructure, which is composed of a shell, a cavity, and a core. The yolk-shell structures have fascinating properties because of their attractive localized surface plasmon resonance (LSPR) feature, which arouses considerable interest in both optically active nanostructures and practical applications. Compared with the single metal nanostructure, a yolk shell has a more controlled degree of freedom, superior optical properties, and potential applications in photocatalysis and solar cell. However, the preparation of yolk shells often requires multiple steps, making it difficult to control the geometric parameters accurately, which leads to uncontrollability of the experimental results. Therefore, it is necessary to study how the size and composition of a yolk shell affect LSPR properties to further guide and optimize the experimental process. Based on the discrete dipole approximation (DDA) method, the absorption spectra, near-field enhancement, and sensing properties of yolk-shell nanoparticles were analyzed. By adjusting the diameters of cavities, cores, shells, and the materials of the shells, we study the influence of yolk-shell structures on the LSPR properties. In detail, the thicknesses of the shells are set from 5 to 20 nm, the diameters of the cavities being set from 50 to 70 nm and the diameters of the yolks are set from 20 to 40 nm. The materials of the shells are set to be dielectric TiO₂ and metallic Au, and both of them have Au cores. It is found that Au@Au yolk shells with large cavities or thick shells have better absorption efficiency, but Au @ TiO₂ yolk shells are just the opposite. For near-field intensity, Au@Au yolk shells are higher than Au @ TiO₂. A yolk-shell structure with larger cavity has smaller full width at half maximum. These results can effectively guide the design of yolk-shell structures for sensing and optoelectronic applications based on LSPR.

In recent years, there has been a growing interest in active metasurfaces. In particular, phase change material-based metasurfaces offering all-optical reconfigurability are being explored. Despite recent progress, further improvement in device reconfiguration energies and optical contrast achievable between the amorphous and crystalline states is desirable. In this work, we demonstrate that using a mirror-backed chalcogenide-based narrowband perfect absorber metasurface can significantly improve the device’s reflection contrast at much lower energies than its mirrorless case. By considering a GST₂₂₅ metasurface operating in the near IR, our systematic numerical study finds improved reflection contrast (up to −32 dB, Q-factor 19.22 compared with 9.59 dB, Q-factor 11 for the mirrorless case). For the mirrored case, the thermal study finds faster crystallization (up to 6 times) at reduced reconfiguration thresholds (72 times lower) compared with the mirrorless case. This results in a more than 2 orders of magnitude higher device figure of merit [defined as the change in reflection contrast (in dB) to a corresponding change in optical energy (in nJ)] compared with the mirrorless case. The results are promising for high-performance metasurfaces at reduced switching energies.

We have proposed reticulated photonic crystals (PhCs) on the top surface of conventional light-emitting diodes (LEDs) to increase the light extraction efficiency (LEE). The rigorous electromagnetic simulations based on the three-dimensional finite-difference time-domain method were carried out to investigate the optical properties of reticulated PhCs LEDs and mechanisms of reticulated PhCs improving the LEE of LEDs. Results from these simulations showed that more than 115% enhancement of LEE had been achieved for LEDs with reticulated PhCs period of 200 nm and depth of 200 nm. This study provides an innovative approach to the creation of high-efficiency LEDs of the upcoming generation.

Thermal imaging, particularly LWIR imaging, has several applications in commercial and security systems. The fundamental problem with the development of metalens is the lack of appropriate materials for LWIR applications. The development of silicon metalens is hampered by the material’s own LWIR spectral band absorption, although silicon is the ideal material for lithography due to its widespread use in CMOS applications. In this study, metalens working on LWIR spectral band has been designed and fabricated using the highly suitable material germanium and low-cost silicon. The focusing and imaging capacity of two types of metasurfaces has been investigated, and a comparison of the results has been presented in the paper.

A simulation framework is developed for the two-dimensional finite-difference time-domain to model multilayer photonic crystal structures. The framework includes the recording process in a photosensitive material through a coherent light source and then a subsequent interrogation with a broadband spectrum. Moreover, the tunable response of the photonic crystal is simulated for different film thicknesses (recorded from 5 to 20 μm), refractive indices contrast (ranging from 4% to 24%), film expansions (interrogated with expansions ranging 110% to 160%), and lattice spacings (recorded with wavelengths from 360 to 560 nm). A parallelization method was implemented in a computer cluster to alleviate the required high computational demand. Through this simulation framework, it is now possible to retrieve relevant information about realistic photosensitive multilayer structures. This method will support the design of multilayer structures utilized in sensors, lasers, and other functional nanostructured photonic devices.

We propose the multilayer silver-silica-graphene-based very large-scale integration interconnects assisted by a tunable perfect absorption structure over the infrared frequency spectrum of the third window of the optical communication for three-dimensional (3D) integrated circuits (ICs). This absorber is numerically investigated for the different cylindrical silver resonator-based squared geometries. The overall structure is investigated for the wavelength range of 1.4 to 1.6 μm over the infrared spectrum. The adjustable behavior of the absorption spectrum is observed when this structure is studied for various chemical potentials of the graphene sheet. We also present the electric and magnetic field intensity for the nearly perfect absorption conditions to identify the effect of energy concentration over different pixel structures and wavelengths. We also showcased the possible fabrication process for the proposed numerical investigation analysis. Resonator height and width have also been simulated numerically to find the resonance shift in the absorber. The adaptable behavior of the suggested structure has potential applications in a wide range of scientific fields, including biosensors, solar absorbers, optical communication, and the fabrication of 3D ICs. Simulations are performed using the COMSOL Multiphysics software module

To generate resonance in the ultraviolet (UV) wavelength region, we have developed a Bragg mirror structure with a SiO₂ top layer. This paper shows the wavelength at which sensitivity occurs by modifying the architecture of the one-dimensional photonic crystal (1D-PhC) structure appropriately. The structural parameters are adjusted to excite a Bloch surface wave with a wavelength of 256 and 281 nm at the top interface, which are the operational wavelengths. The spectrum’s distribution of electric fields and mode confinement confirmed the suggested structure with an 8-nm thick defect layer. The proposed design is empathetic at UV wavelength with varying analyte’s refractive index value. The investigation shows that the sensitivity is about 107.42 and 101.85 deg/RIU, and the quality factor is 1426.17 and 1708.14 nm at UV wavelengths of 281 and 256 nm, respectively.

Strong couplings between localized surface plasmon resonance (LSPR) modes and single quantum emitters have been intensively investigated recently, and meanwhile the coupling between different LSPR modes inside individual metallic nanoparticle is still rarely researched. Herein, the strong coupling is investigated for different LSPR modes inside individual rectangular-grating-shaped gold nanostructure composed of one main-cuboid and two side-attached subcuboids. Original uncoupled LSPR modes are revealed to be longitudinal and U-shaped LSPRs. For the nanostructure with increased main-cuboid length, the dispersion curves of simulated dual-original LSPR scattering wavelengths and dual-coupled LSPR scattering wavelengths show typical strong coupling patterns featuring anti-crossing and large Rabi splitting of 598.1 meV. The strong coupling is considered to be caused by the overlap of longitudinal and U-shaped LSPR oscillation modes in the gold nanostructure. The extracted coupling strength is found in order of 10¹³ Hz and it increases with the LSPR overlap length. The spatial mode and time evolution of the coupled LSPR modes are also numerically investigated. The simulated results are well comprehended with the classical strong coupling model of oscillators, further confirming the coupling between the longitudinal and the U-shaped LSPRs. The experimental dark-field scattering spectrum shows the existence of U-shaped LSPR mode in the gold nanostructure.

Numerical simulations have become an essential design tool in the field of photonics, especially for nanophotonics. In particular, 3D finite-difference-time-domain (FDTD) simulations are popular for their powerful design capabilities. Increasingly, researchers are developing or using inverse design tools to improve device footprints and performance. These tools often make use of 3D FDTD simulations and the adjoint optimization method. We implement a commercial inverse design tool with these features for several plasmonic devices that push the boundaries of the tool. We design a logic gate with complex design requirements as well as a y-splitter and waveguide crossing. With minimal code changes, we implement a design that incorporates phase-encoded inputs in a dielectric-loaded surface plasmon polariton waveguide. The complexity of the requirements in conjunction with limitations in the inverse design tool force us to make concessions regarding the density of encoding and to use on–off keying to encode the outputs. We compare the performance of the inverse-designed devices to conventionally designed devices with the same operational behavior. Finally, we discuss the limitations of the inverse design tools for realizing complex device designs and comment on what is possible at present and where improvements can be made.

We present a germanium “Ge-on-Si” CMOS image sensor with backside illumination for the near-infrared (NIR) electromagnetic waves (wavelength range 300 to 1700 nm) detection essential for optical sensor technology. The microholes help to enhance the optical efficiency and extend the range to the 1.7-μm wavelength. We demonstrate an optimization for the width and depth of the microholes for maximal absorption in the NIR. We show a reduction in the crosstalk by employing thin SiO₂ deep trench isolation in between the pixels. Finally, we show a 26 to 50% reduction in the device capacitance with the introduction of a microhole. Such CMOS-compatible Ge-on-Si sensors will enable high-density, ultrafast, and efficient NIR imaging.

Motivated by atomic response to different initial coherent optical fields, we comparatively studied transient population grating (TPG) induced by successive pulse train. Time delay and pump pulse duration dependence of TPG is achieved by numerically solving the density matrix equations. Results reveal that the creation and erasure of TPG is possible by choosing the appropriate pulse parameters, which is illustrated by Bloch sphere model and quantitative validation. To obtain desired large grating amplitude for rectangular pulse, the allowed pulse duration can be extended to one order wider than that of Gaussian pulse. Population grating can be erased to near zero by a third pulse with time delay by an odd multiple of half the pulse width, and it also can be erased further to recover atom assembly back to the initial state by a fourth pulse with time delay equal to an integer multiple of pulse width. Atomic behaviors excited by different types of pulse presented here may be significant to manipulate TPG during coherent light-matter interaction.

We study an independently tunable Fano resonance from quasibound state in the continuum and polarization-independent toroidal dipole resonance in hybrid graphene–dielectric metasurface consisting of a nanoring and a cross-shaped nanobar. The unique structural properties of the proposed metasurface can support directional toroidal dipole mode, where the asymmetric magnetic field enhancement can be dynamically switched on and off while maintaining polarization-independent Fano spectral response. Through reducing or increasing inner radius of nanoring, an additional quasi-BIC dominated by magnetic dipole moment can be excited and independently tuned by altering the polarization direction of the incident wave. In addition, the quasi-BIC can be effectively modulated via adjusting the Fermi energy and layer numbers of the graphene. Our results can be of practical interest for a variety of applications including optical modulator, filter, switches, and light trapping.