This is a list of reviewers who served the Journal of Nanophotonics in 2020.

The canonical boundary-value problem for Dyakonov-surface-wave propagation in a fixed direction guided by the planar interface of a uniaxial dielectric material and an isotropic nondissipative dielectric material was solved. Both partnering materials were taken to be homogeneous and the constitutive parameters for both to lie within the ranges of available materials. Solutions were found for which the phase speed of the Dyakonov surface wave is greater than the phase speed of a plane wave in the bulk isotropic partnering material.

In the current study, the linear combination operator (LCO) and Lee–Low–Pines unitary transformation (LLPUT) are adopted to verify the effect of the anisotropic parabolic potential (APP) on the polaron’s properties in the asymmetric Gaussian quantum well (AGQW). Relations of the vibrational frequency (VF) and the ground state energy (GSE) of weak coupling polaron in the AGQW for GaAs crystal varying with the effective confinement strengths of the APP, the barrier height, and range of the asymmetric Gaussian confinement potential (AGCP) are derived. The numerical calculated results illustrate that the GSE and VF of the weak coupling polaron in the AGQW can increase according to the effective confinement strengths’ growth for given values of the barrier height and range of the AGCP. They will increase by increasing the barrier height of the AGCP. However, they are decreasing functions of the range of the AGCP for the determined values of the effective confinement strengths and the barrier height of the AGCP.

The enhanced Fabry–Perot (F–P) resonance caused by adding a layer of AlN film to different metal substrates (AlN/metals) was analyzed by controlling the thickness of AlN film. The obtained results using the finite-difference time-domain (FDTD) method show that the absorption capacity of visible light was changed by the film interference effect. Then, the light absorption of Au/AlN/Fe (AAF) trilayer structures exhibits that the addition of the ultra-thin Au layer to the AlN/Fe surface improves the light absorption, the color gamut, and purity. Both the transfer-matrix theory and Fresnel–Airy equation were used to compare the FDTD simulations, the calculations show that all the results are consistent. Systematic analyses revealed that AlN film as an F–P resonant cavity is a promising strategy for optical applications, and AAF is an ideal structure in the applications to optical filters, no-ink printing, and optical anti-counterfeiting.

We numerically analyzed the influence of geometric structures of gradient Al component Al_xGa_{1  −  x}N nanowire on their light-trapping properties, ranging from nanopillars, inverted conical frustums, to inverted hexagonal frustums. COMSOL^® Multiphysics package based on the finite element method is used to systematically study the effects of geometric parameters such as base radii (R), pillar height (H), period (P), and angle of incident light on the optical absorption. The simulation results show that compared with the other nanostructure counterparts, the inverted hexagonal frustum can effectively couple photons into the nanoarrays to achieve wide spectrum and effective optical absorption for Al_xGa_{1  −  x}N nanowire-based UV photocathode. The inverted hexagon frustum with optimum height can obtain an optical absorption above 95% over a wide wavelength of 200 to 380 nm and a broad angle of incident light between 0 deg and 70 deg. All these findings not only show that the gradient Al component Al_xGa_{1  −  x}N material has a great potential advantage for the UV photocathode, but it also provides an efficient broadband and omni-directional light trappers for the UV photocathode.

A plasmonic structure, constituted by metal insulator metal waveguides and split annular cavity connected with rectangular resonator (SACRR), is proposed and investigated. Numerical simulation by the finite element method (FEM) has been done to investigate the transmittance properties of the proposed structure and four Fano resonances arise in the results. To analyze and verify the simulation results, multimode interference coupled mode theory is engaged, theoretically. In addition, the structural parameters are analyzed and discussed to design and control the proposed structure, which shows sufficient flexibility. Due to multi-Fano resonances providing multiple monitoring points and the extremely sharp asymmetry of Fano resonance, the structure can service as a high-performance multichannel refractive index nanosensor with a sensitivity of 1000 nm/RIU and maximum figure of merit of 1.358  ×  10⁵. The designed structure can surely meet extensive applications for nanoscale devices and integrated optical devices.

Plasmonic metasurfaces with in-plane phase elements have a limit in transmission because they only affect the electric field of incident EM radiation. Recently, a set of out-of-plane plasmonic phase elements was designed using a genetic algorithm to work in the infrared as a Huygens metasurface with significantly improved transmission efficiency. A beam-steering metasurface (i.e., blazed transmissive diffraction grating) was fabricated from this design using membrane projection lithography (MPL) and characterized for its bidirectional transmittance distribution function as a function of scatter angle for normally incident light, and linear incident and transmitted polarizations. Measurements were compared with the designed behavior as predicted by finite element method (FEM) simulations that generated near fields for each phase element and propagated them to the far field as a metasurface using a Stratton–Chu formulation, but measurements showed strong zero-order diffraction not present in the simulation along with the designed +1-diffraction order. We analyze this disagreement between measured and ideal results. Further FEM modeling included the introduction of defects into the phase elements consistent with defects expected from the fabrication process and identified lateral displacement of the plasmonic decoration in the MPL structure as a potential cause for the reduced performance of the fabricated device.

A plasmonic refractive index (RI) sensor based on photonic crystal fiber is proposed. A chemically stable thin film of gold (Au) is used as an active plasmonic layer and high RI material Ta₂O₅ is used as an overlayer over the gold thin film. The effect of Ta₂O₅ thin film on the sensor performance is analyzed in detail and a novel, as per the authors’ best knowledge, operating analyte RI range tunable property is reported. It is observed that the operating range is tuned toward the lower RI region with increasing Ta₂O₅ layer thickness. Furthermore, the sensor is optimized and its sensitivity is realized using both wavelength and amplitude interrogation techniques. A maximum wavelength sensitivity and amplitude sensitivity of 16,354 nm/RIU (refractive index unit) and 1574  RIU^−  1, respectively, are obtained corresponding to the operating RI range of 1.39 to 1.41 for the optimized structure. Moreover, the detection accuracy of the sensor is found of the order of 10^−  6 with a high figure of merit up to 282 representing an overall good sensing performance. The sensor performance is realized using surface plasmon resonance phenomenon and numerically analyzed using finite element method. Our study, no doubt, provides a new direction of designing RI sensor that could tune the RI range to the desired operating range. In addition, the simple design feasibility, low fabrication cost, and portable nature of the proposed sensor make it suitable for industrial and chemical sensing applications.

We experimentally investigated simultaneous microfluidic control and visualization of a heated region using gold nanoisland/VO₂ thin films. By focusing a laser on the film, we photothermally generated an air microbubble in nondegassed water. After the bubble generation, another laser spot was irradiated 48  μm away from the bubble center. As a result, a sudden onset of the rotational Marangoni flow was observed at 130 ms after the laser was turned on. At the same time, the heated region above 70°C was visualized based on the thermochromic property of the thin film. The heated area did not vary significantly at the onset of the flow, indicating that there is a threshold temperature or temperature gradient on the bubble surface for generating the rotational Marangoni flow. To understand the flow generation, we decreased the distance between the bubble and the laser spot. The resulting visualized heated region suggests that a part of the bubble surface has to be heated above 70°C to generate the rotational flow. In addition, the heated area during the flow generation remained small as the distance decreased. The gold nanoisland/VO₂ thin film is suitable for understanding and optimizing the rapid Marangoni flow generation.

In recent years, antibody-labeled fluorescent probes have attracted wide attention in fluorescence immunochromatography. Quantum dots (QDs) are excellent fluorescent materials with some unique optical properties, including strong stability against photobleaching, broad excitation spectra, high emission intensity, good fluorescence efficiency, and narrow excitonic emission. The CdSe/ZnS QDs microbeads were prepared by encapsulation in-situ of CdSe/ZnS QDs in polyisobornyl methacrylate (PIBOMA) herein and then functional QDs microbeads were produced by the binding of active carboxyl-modified QDs microbeads to the C-reactive protein (CRP) antibody. Their fluorescence properties were also investigated and functional QDs microbeads were further evaluated as fluorescent probes to detect different CRP concentrations using the fluorescence immunoassay test strips. The experiment data indicated that functional QDs microbeads possessed good stability, high fluorescence efficiencies, narrow fluorescence spectra, and good linear relationship of detection line signal versus quality inspection line signal (T₁  /  C) to the CRP concentration varying from 0.001 to 0.2  mg  /  l. Therefore, functional CdSe/ZnS QDs microbeads encapsulated in PIBOMA bioconjugated to CRP antibody can be used as the potential fluorescent probes to achieve quantitative detection in the immunochromatographic technology.

In this work, a photonic sensor based on photonic crystal fiber and surface plasmon resonance to analyze the refractive index (RI) of analytes varying from 1.440 to 1.480 is presented. A dual hexagonal lattice of air holes is reported in this proposed sensor design. The combination of titanium dioxide (TiO₂) and gold (Au) is used as a plasmonic material in this sensor. The sensing capability of the proposed sensor is inspected in terms of wavelength sensitivity, amplitude sensitivity, sensor resolution, linearity of resonance wavelength, and figure of merit (FOM). Theoretical analysis of the sensor is performed for both quasi TM mode and quasi TE mode. Numerical investigation shows that wavelength sensitivity of 12  ,  000  nm RIU^−  1, is obtained for both TM mode and TE mode using the wavelength interrogation method. AS of 3307 and 3619  RIU^−  1 is obtained for TM mode and TE mode, respectively, using the amplitude interrogation method. A maximum sensor resolution of 8.33  ×  10^−  6  RIU is obtained for both TM mode and TE mode, respectively. The linear relationship of resonant wavelength with RI produces R²  =  0.9991 and R²  =  0.9970 for degree 2, for TM mode and TE mode, respectively. The FOM obtained from the proposed sensor is 139.53 and 187.50 for TM mode and TE mode, respectively.

We report on surface-enhanced Raman scattering (SERS) activity of bimetallic core-shell Au@Ag nanorods. These nanostructures feature four plasmon maxima in the UV-visible range. Their application for SERS analysis enables matching individual optical properties of organic analytes using the optimal excitation wavelength resonant both for plasmon nanostructures and analytes. It promotes higher sensitivity of surface-enhanced resonance Raman scattering (SERRS) of specific analytes. The intensity of SERRS spectrum is higher up to 2 orders of magnitude for alizarin and up to 4 times for malachite green as compared to the corresponding SERS spectra. Thus Au@Ag nanorods can be used as a single SERRS substrate for sensitive analysis of a number of dyes.