To improve stability, we proposed a strategy of coating ZnO with CsPbBr3 quantum dots (QDs). The luminescence performance of CsPbBr3 QDs can be significantly enhanced by coating ZnO with CsPbBr3 QDs. Importantly, CsPbBr3-ZnO QDs exhibited higher stability under ultraviolet light and thermal conditions, retaining 67% and 72% of their photoluminescence (PL) intensity after seven cycles of heating and cooling and 7 h under 365-nm ultraviolet light. Time-resolved PL spectra revealed that the increase in the average lifetime of CsPbBr3-ZnO QDs mainly comes from the increase in radiative recombination and the decrease in non-radiative recombination (including surface state recombination and defect-level-related recombination). In addition, we fabricated green light-emitting diodes with CsPbBr3-ZnO QDs, which show great potential in the field of display screens.
Chiral metasurfaces with dual-band circular dichroism (CD) hold significant promise for advancing polarization-sensitive imaging, molecular sensing, and wavelength-division optical communication. However, simultaneously achieving high CD values (>0.8) and precise dual-wavelength selectivity within sub-100 nm spectral ranges remains a significant challenge. This challenge is addressed through a dielectric metasurface design that exploits distinct multipolar resonances. Under right-handed circularly polarized light incidence, a magnetic quadrupole (MQ) mode at 1482 nm enables cross-polarization conversion (T-LR=0.87, CD = 0.82), whereas a magnetic dipole (MD) mode at 1533 nm sustain co-polarized transmission (TRR=0.88, CD = 0.83). The ultra-narrow 51 nm band separation demonstrates new possibilities for multiwavelength polarization manipulation in integrated photonic systems. Furthermore, this structure exhibits remarkable refractive index sensing capabilities. The MQ mode shows a real-part sensitivity of 161 nm/RIU and an imaginary-part sensitivity of 65,259 RIU-1, whereas the MD mode achieves a higher real-part sensitivity of 423 nm/RIU, along with an imaginary-part sensitivity of 33,591 RIU-1. We provide a new strategy for designing compact, high-performance chiral metasurfaces with dual-band selectivity, particularly valuable for wavelength-multiplexed chiral sensing and ultra-dense photonic circuits.
Efficient conversion of mid-infrared (MIR) radiation into electricity remains a challenge for thermoelectric devices. We present multiresonant Ag-Si:B-Ni bowtie cross nanoantenna (BCN) arrays that exploit plasmon-enhanced photothermal effects to achieve broadband MIR absorption and voltage generation via the Seebeck effect. The 9 & times;9 BCN arrays, fabricated by electron beam lithography, exhibit multiple plasmonic resonances from 18 to 48 THz with a similar to 30 THz bandwidth. COMSOL simulations reveal strong field confinement and open-circuit voltages up to 11.19 mu V under 1000 W & centerdot;m2 illumination, which are experimentally validated by Fourier Transform Infrared measurements. The broadband response, geometry-dependent tunability, and efficient heat-to-electric conversion establish BCNs as promising candidates for waste-heat harvesting, MIR sensing, and plasmonic metasurface thermoelectrics.
In this study, we present a biosensor that utilizes a microfluidic approach to fabricate nematic liquid crystal (NLC) microspheres for the detection of phospholipase A1 (PLA(1)), a biomarker associated with Alzheimer's disease (AD). We fabricated uniform-diameter NLC microspheres using a custom-designed microfluidic chip and functionalized them with phosphatidylcholine (PC), which promotes radial arrangement. Subsequently, the NLC microspheres transitioned from a radial to a bipolar arrangement through hydrolysis of PC by PLA(1).This method offers the advantage that the detection process can be directly observed using a polarizing microscope (POM). Eventually, image binarization is applied to enhance detection sensitivity, reducing the detection limit of PLA(1) to 400pg/mu L. Additionally, the detection time is shortened by more than twelve-fold compared to traditional methods. The rapid response capability of NLC microspheres holds significant potential for the detection of various diseases and biomarkers. This technology could be further developed into a low-cost, rapid, and portable diagnostic tool.
A high extinction ratio modulator using the epsilon-near-zero (ENZ) material of cadmium oxide (CdO) is proposed. The proposed device consists of a shoulder-coupled cavity at the middle of a photonic crystal (PC) structure where input light is coupled through a PC line defect waveguide. The shoulder-coupled resonant cavity is infiltrated with high mobility CdO. The structure is simulated by the two-dimensional finite-difference time-domain method. According to the presented results, a high extinction ratio of 21.32 dB as well as a low insertion loss of 0.22 dB around the operating wavelength of 1.55 mu m are achieved when a low voltage of 3.18 V is applied to the ENZ material. The modulation speed is as high as 14.4 GHz. Owing to the high quality-factor resonance of 1244, a strong field localization in the microcavity is obtained. The proposed modulator based on the high-mobility ENZ material of CdO could have a promising impact on future optical communications systems.
Photonic Crystal Light Sails offer an innovative way to achieve propellant-free space propulsion by enabling continuous laser-driven acceleration with minimal onboard mass. We detail the design, simulation, and fabrication of nanoscale photonic crystal structures comprising three dielectric regions: high-index germanium pillars, air holes, and a low-index PMMA matrix. Using the finite-difference time-domain and plane-wave expansion methods, we evaluate various photonic crystal slab patterns and identify configurations that exhibit photonic band gaps with high reflectivity in a structure primarily composed of voids. These gaps provide high reflectivity at laser-propulsion wavelengths while remaining transparent across most of the electromagnetic spectrum, thereby reducing thermal loads. Fabrication was carried out using electron-beam lithography and vacuum deposition at the Center for Nanophase Materials Sciences at Oak Ridge National Laboratory, yielding proof-of-concept devices with controlled nanoscale features. Samples show the feasibility of integrating three different dielectric materials into robust photonic crystal membranes. Challenges related to scaling up to three-dimensional multilayer structures are discussed, with plans to explore alternative materials and advanced fabrication techniques.
Plasmonic metasurfaces enable exceptional control over subwavelength light-matter interactions, but their practical applications are often hindered by intrinsic ohmic losses in metals, which limit the achievable quality factors (Q-factors). Surface lattice resonances, arising from collective diffraction-mediated coupling in periodic nanoparticle arrays, offer a pathway to overcome this limitation by supporting spectrally narrow resonances. We present a design of metasurfaces consisting of metallic ellipse-shaped unit cells embedded in a homogeneous silica environment. Through numerical simulations, we show record Q-factors of similar to 9100 and similar to 5500 for gold and silver nanoparticles, respectively. The Q-factors show strong dependence on geometric parameters of the unit cell, thus requiring tight fabrication tolerances. Moreover, we examine how imperfections from lower-quality metals affect the Q-factors and find that they remain relatively stable for such defects. The ultrahigh-Q metasurfaces can be used for advanced nanophotonic applications such as nonlinear optical processes, optical filtering, and highly sensitive detection. (C) 2025 Society of Photo-Optical Instrumentation Engineers (SPIE)
We present a deep-learning-optimized bidirectional metamaterial perfect absorber (BMPA) that achieves switchable dual-mode operation for narrowband sensing and broadband energy harvesting. The proposed BMPA integrates a multilayer architecture of Al, Si3N4, MgF2, Au, and Ti, with structural parameters optimized via a neural network trained on numerically simulated datasets. Under top illumination, the absorber exhibits narrowband responses with four distinct peaks at 725, 820, 1005, and 1180 nm, each exceeding 98.69% absorptance and offering exceptional spectral selectivity. Under bottom illumination, the device switches to broadband absorption across 740 to 1830 nm, maintaining >90% absorptance and an average absorptance of 97.45%. The bidirectional absorption arises from coupled plasmonic and Fabry-P & eacute;rot resonance mechanisms, enabling multifunctional performance within a simplified design. Furthermore, the BMPA demonstrates polarization insensitivity and robust stability up to 60-deg incident angle, making it well suited for diverse applications in optical sensing, solar energy harvesting, and reconfigurable photonic devices. We introduce a practical strategy for overcoming the limitations of conventional photonic absorbers by combining deep learning optimization with multifunctional tunability in a single compact platform.
We present an all-optical full-adder (FA) design that employs the technique of power combiner and divider, as well as Y-shaped plasmonic metal-insulator-metal waveguide in a compact size of 20 mu mx12 mu m and wavelength of 1.55 mu m. The combiner tends to make use of the linear interference principle to achieve the desired output. The preferred all-optical FA design has an extinction ratio (ER) of 10.96 dB for sum, 11.54 dB for carry. In addition, various other characteristics, such as transmission rate (69.5%), bit rate (sum = 10.25 Tbps and carry = 13.8 Tbps), response time (sum = 105 fs and carry = 71 fs), and insertion loss (sum = 2.22 dB, & carry = 0.13 dB) have also been simulated and calculated.
We predict a positive effect of metal nanoparticles on optical limiter performance. For genuine two-photon absorbers, the effect is straightforward and comes from incident local field enhancement. The only apparent limitation may result from intrinsic metal absorption and dissipation, which requires the designer to keep the volume fraction of metal low enough. For optical limiting based on two-step processes and known as reverse saturable absorption (RSA), the positive effects from plasmonic nanostructures exist only if the local incident intensity rise is higher than the total decay rate enhancement in the proximity of metal nanoparticle(s). The enhancement of RSA-limiter performance is readily attainable with Ag and Au nanoparticles for low intrinsic quantum yield, which is typical for efficient RSA molecules such as metalloporphyrins and metallophtalocyanines. The consideration also holds for genuine absorption saturation and can be used in the design of saturable absorbers for Q-switched and mode-locked lasers.
This work presents a high-performance metamaterial absorber (MMA) designed for efficient solar energy harvesting across a broad spectral range from 100 to 1000 nm. The absorber features a compact unit cell measuring 100x100x12 nm(3), incorporating nickel as both the resonator and ground layers, with quartz serving as the dielectric substrate. High broadband absorption is achieved through a multi-faceted mechanism: First, the structural parameters are carefully optimized to realize near-perfect impedance matching with free space, thereby suppressing reflection at the interface. Second, the metal-insulator-metal configuration facilitates the strong hybridization of localized surface plasmon resonances, which collectively broaden the absorption spectrum. Finally, the introduction of the dielectric spacer enables strong magnetic resonance due to anti-parallel surface currents, which confine the magnetic field and significantly enhance dissipation within the nickel layers. The proposed MMA demonstrates exceptional broadband absorption exceeding 90% across the 130- to 1000-nm wavelength range, with an average absorption of 96.63% considering the entire 100- to 1000-nm span. Notably, a peak absorption of 97.57% is observed at 201 nm, whereas the proposed structure achieves over 99% absorption consistently within the 700- to 900-nm near-infrared region. Electromagnetic field analyzes encompassing electric field distribution, magnetic response, surface current flow, and effective parameter retrieval offer insights into the underlying absorption mechanisms. Excellent polarization insensitivity up to 60 deg has also been demonstrated by the proposed MMA. In addition, a machine learning framework was developed to enhance predictive modeling of the absorber's behavior, using five advanced algorithms across three test scenarios. Among these, the extra trees regressor achieved superior performance with a validation accuracy of 99.91% and 99.96% for both resonator and substrate thickness, respectively. The absorber also yields a high solar absorption efficiency of 95.87%, indicating strong potential for use in next-generation solar energy harvesting applications.
We designed a multifunctional chiral metasurface comprising vanadium dioxide (VO2), a polyimide (PI) dielectric layer, and an aluminum substrate. The metasurface can switch between circular dichroism (CD) and wavefront modulation in the terahertz regime by taking advantage of VO2's temperature-based phase transition. When VO(2 )is in the dielectric state (sigma=200S/m), the metasurface shows a large CD up to 0.93. Moreover, by changing the temperature, the CD can be adjusted from 0.93 to 0.01. When VO(2 )is in a metallic state (sigma=2x10(5)S/m), we designed a metalens based on the Pancharatnam-Berry (PB) phase, achieving a focal length of 1003.8 mu m and NA approximate to 0.85. Furthermore, by arranging meta-atom reasonably, we obtained two orbital angular momentum (OAM) generators capable of generating vortex beams with topological charges of 1 and 2. Besides, the mechanics of the metasurface to produce CD and OAM were also analyzed theoretically.
In recent years, the demand for high-resolution, highly integrated, and low-cost three-dimensional intelligent sensors in fields such as autonomous driving has been continuously increasing. Optical phased arrays (OPA), with their integration, high beam scanning rate, and excellent reliability, have gradually become one of the hot research topics in the LiDAR field. Here, we propose a mode-multiplexed OPA system. Two longitudinal vertical modes use the same one-dimensional double-layer planar grating as a single emission source to achieve beam steering. The results show that a 97 degx30 deg beam scan is achieved in the field of view, and the wavelength tuning efficiency is as high as 0.3 deg/nm, which provides ideas for the development of OPAs in the LiDAR systems.
Metal doping is one effective way to improve the optoelectronic characteristics of hybrid perovskite compounds. We examine the influence of copper (Cu), silver (Ag), and gold (Au) doping on the photovoltaic and optical properties of the room temperature stable tetragonal phase of methylammonium lead iodide (MAPbI3). Density functional theory (DFT) computations were used to calculate the electronic structure and optical absorption properties of undoped and doped MAPbI3 systems. It is observed from the results that Au and Cu doping could greatly improve the absorption in the 550 to 900 nm wavelength range by 7.77% and 21.13%, respectively. Doping with Ag causes absorption to decrease by 6.47%. To evaluate the device-level performance, DFT absorption profiles were integrated into SCAPS-1D simulations. The Au-doped MAPbI3 showed the best predicted power conversion efficiency (PCE) of 19.12% via a short-circuit current density (Jsc) of 68.20 mA/cm2. Cu-doped devices realized balanced performance at 14.91% PCE, whereas Ag doping resulted in the lowest efficiency at 13.80%, caused by decreased light absorption and enhanced series resistance. These findings identify the potential of noble metal doping, particularly with Au and Cu, to improve the photovoltaic efficiency of MAPbI3-based solar cells. Theoretical predictions are made as a roadmap for future experimental validation. Constraints due to the omission of spin-orbit coupling and the idealized nature of SCAPS simulations are considered, and directions for future research are indicated. (c) 2025 Society of Photo-Optical Instrumentation Engineers (SPIE)
Mode converters play a critical role in on-chip photonic mode field manipulation systems. This paper proposes a topology optimization method for mode converters based on B-spline parameterization. The initial structure's density field is represented using B-spline surfaces, with the density values determined by control coefficients. The control coefficients are iteratively optimized using the sequential quadratic programming algorithm. The optimized TE0-TE1, TE0-TE2, and TE3-TE1 mode converters, with footprints of 2 mu mx1.6 mu m, 2 mu mx1.6 mu m, and 2 mu mx1.9 mu m, respectively, achieve average conversion efficiencies of 93.38%, 88.39%, and 88.83% over bandwidths of 400, 290, and 340 nm. Their maximum conversion efficiencies are 98.62%, 92.45%, and 92.72%, respectively. By cascading these mode converters, arbitrary-order mode conversions among TE0, TE1, TE2, and TE3 can be realized. The method demonstrates great potential for application in nanophotonic device design, providing an effective solution for high-capacity optical communications and optical interconnects.
Deep learning has emerged as a transformative approach for on-demand inverse design of chiral metamaterials and nanophotonic devices. However, the inherent black-box nature of neural networks (NNs) poses significant challenges in interpreting the multimodal optical responses predicted by data-driven models. We develop a hybrid architecture that integrates an expanding-width NN with a Gaussian parsing NN to achieve spectral decoding and inverse design of chiral plasmonic nanoantennas. The expanding-width NN adopts a neuron-doubling architecture across successive layers, effectively broadening gradient propagation pathways to mitigate vanishing gradients, thereby enabling accurate predictions of nanoantenna scattering, absorption, and near-field spectra (mean squared error <0.0077). Importantly, the Gaussian parsing NN decomposes complex plasmonic spectral responses into fundamental eigenmodes, quantitatively resolving critical parameters such as the dominant mode count, linewidth, and resonance wavelengths. Furthermore, we utilize this framework to establish an end-to-end mapping from geometric parameters to tailored plasmonic modes that govern circular dichroism and Fano resonance. Our methodology not only bridges data-driven design with physical interpretability but also paves the way for new applications in topological photonic circuits, single-molecule biosensors, and hyperspectral computational imaging. (c) 2025 Society of Photo-Optical Instrumentation Engineers (SPIE)
We numerically study a resonant planar chiral dielectric metasurface that can be constructed to realize low-threshold lasing. The designed metasurface is made of a periodic array of a square lattice of a slanted ring formed by two half-rings staggered from each other placed on a glass substrate and supports chiral quasi-bound states in the continuum dominated by the magnetic quadrupole. Exploiting the chiral quasi-bound states in the continuum (BIC) response with high Q-factor and strongly localized fields inside the ring, we study the lasing action of the slanted ring. The results reveal that the chiral quasi-BIC exhibits the polarization-dependent threshold. We theoretically demonstrate that the threshold can be reduced to 6.72 and 8.11 mu J/cm(2) for left and right circularly polarized pumping, respectively. These results promise various practical applications including chiral emission and lasing applications. (c) 2025 Society of Photo-Optical Instrumentation Engineers (SPIE) [
