A metalens is an advanced optical element that uses a metasurface—an array of nanoscale resonators (NRs)—to manipulate light at the subwavelength scale. In contrast to conventional lenses, which focus light through curved glass or plastic surfaces, metalenses control optical wavefronts by precisely engineering the geometry, dimensions, and spatial arrangement of NRs. This approach enables effective aberration correction and high focusing efficiency and resolution, while offering a significantly thinner and lighter form factor compared to traditional lenses.

The widely used approach to design a metalens starts from the generation of a Look-Up Table (LUT), i.e., a pre-calculated library containing dissimilar NRs that can impart a phase in the 0-2π range by simply tuning a few geometrical parameters. Once the LUT is generated, the NRs are carefully placed in the metalens to assign, at every spatial point, the required phase to achieve the desired performance. However, to compute the LUT, the NRs are usually placed in a perfectly periodic array, an assumption that fails when the NRs are then displaced into the real metalens. Thus, the LUT method implies an intrinsic error limiting its performance. Some recent studies have raised concerns regarding the reported performance of metalenses in the existing literature. For this reason, the modelling of a full metalens to evaluate its actual focusing efficiency, and methods beyond the standard LUT approach for the metalens design, are necessary.

In this work, we consider a 2D cylindrical metalens focusing light in the NIR range. After calculating the LUT and engineering the metalens, we first evaluate its actual performance and then we envision how to improve them.

Colloidal suspensions are essential and found in various nano- and micro-scale engineering and scientific fields, such as slurries in chemical engineering, colloidal photocatalysts in environmental remediation, and milk in food science. High concentrations are in high demand across various industries, such as for improving product quality and reducing transport costs by reducing the weight of suspensions. The development of a method to non-destructively evaluate particle properties (such as particle size distribution and aggregation degree) of high-concentration colloidal solutions is urgently needed. Light-scattering techniques have been extensively developed as promising tools for evaluating particle properties. Meanwhile, most developed techniques require sample dilution, with the volume fraction typically less than 5%. Thus, the method is still under development. For this development, simultaneous and appropriate modeling of the particle properties and light scattering, along with a fast solution method, is essential. In this study, a fast calculation method was developed based on the local monodisperse approximation to the dependent scattering theory (DST). Previously, we proposed a rapid method for polydisperse systems without particle agglomeration; here, we extended it to agglomerated systems. The DST describes the far-field interference between the scattered electric fields in dense colloidal systems. We successfully achieved a speedup of over 800 times in computation, while maintaining the same accuracy in describing the DST results. Our findings provide forward modeling for developing nanotechnology to evaluate the particle properties non-destructively using scattered light.

LED lighting in urban areas has expanded exponentially over the years, mainly due to its energy and cost savings. Currently, most LED street lights operate at a constant power output, regardless of traffic and pedestrian activity. In this research, a simulation is developed using MATLAB software to design different adaptive regulation strategies with the aim of further improving the energy efficiency of these lights, while maintaining acceptable visibility conditions.

This work integrates LED photometric data, the behaviour of electronic PWM regulators and the calculation of illuminance on the road surface. Two main control strategies are considered: attenuation profiles according to the time of day and traffic-sensitive attenuation according to car detection events. This approach will allow a comparison to be made in terms of energy consumption, illuminance distribution and essential lighting requirements.

This study will enable both municipalities and designers to evaluate the main characteristics of adaptive lighting using a modelling approach together with test scenarios before its implementation on the streets and on any urban road. A flexible methodology is proposed to enable future research to include real sensor data, environmental factors, and additional attenuation algorithms. This will allow for more accurate assessments in decision-making in smart city applications.

Photon-limited imaging of weak scattering objects is strongly affected by shot noise, leading to reduced contrast and variable phase retrieval. Introduction of phase-encoding elements can improve image formation by converting phase variations into measurable intensity modulations; however, conventional phase plates such as Zernike or vortex designs impose fixed symmetries and often lack robustness when photon budgets are low. This work dives into a simulation-based investigation of random binary phase plates as an alternative encoding approach for photon-limited computational imaging.
Image formation is modelled using scalar diffraction theory and angular-spectrum propagation through transmission phase plates composed of randomly distributed binary phase regions. Low dose detection is explicitly incorporated using Poisson noise statistics. Image recovery is performed using regularized inverse filtering, followed through systematic comparison of different phase-encoding methods devoid of complex reconstruction algorithms.
The results indicate that random binary phase encoding introduces wavefront diversity that possibly improves spatial–frequency mixing and stabilizes image reconstruction under strong shot noise. Relative to conventional symmetric phase plates, the random designs exhibit better CNR [Contrast to noise ratio] and reduced sensitivity to photon loss at detected photon levels below 10³. The dependence of imaging performance on phase-plate feature size is also examined, identifying parameter combinations that enhance noise robustness while maintaining reconstruction fidelity.

INTRODUCTION: Silver nanoparticles (AgNPs) are capable of producing a plasmonic effect, which can amplify the local electric field of certain materials, such as methylene blue (MB), resulting in fluorescence spectra with increased intensity. However, for this effect to occur, two conditions must be met: (i) spectral overlap between the extinction spectrum of the AgNPs and the absorption spectrum of MB, and (ii) an intermediate distance (10–20 nm) between the AgNPs and the material whose electromagnetic signal is to be amplified.

METHODOLOGY: Initially, AgNPs were synthesized using a bottom-up approach by reducing an Ag⁺ solution with NaBH₄, yielding nanoparticles with an extinction band overlapping the absorption band of MB. Subsequently, different volumes of AgNPs (10, 20, and 40 µL) were mixed with MB to obtain a final MB concentration of 10 µmol L⁻¹. A 10 µmol L-1 MB solution without AgNPs was used as a control. Spectrofluorimetric measurements were performed to evaluate the effects on the MB + AgNP systems and on MB alone.

RESULTS: Fluorescence measurements were carried out for each sample, revealing variations in fluorescence intensity relative to isolated MB. Upon the addition of 10, 20, and 40 µL of AgNPs, the fluorescence intensity increased by 5.7%, 2.5%, and 1.7%, respectively. These results indicate that higher volumes of AgNPs did not lead to the further enhancement of MB fluorescence intensity.

CONCLUSION: In conclusion, at the studied concentration, it is possible to achieve an amplification of the fluorescence signal of MB using the synthesized AgNPs; however, the optimal added volume was approximately 10 µL. These findings may contribute to the development of improved outcomes in treatments that employ phototherapy.

INTRODUCTION: Silver nanoparticles (AgNPs) exhibit optical properties associated with surface plasmon resonance, which can enhance the local electric field in the vicinity of molecules such as methylene blue (MB), leading to increased fluorescence intensity. For this amplification to be effective, two criteria must be fulfilled: (i) spectral overlap between the extinction spectrum of the AgNPs and the absorption spectrum of MB; and (ii) an appropriate distance, estimated to be between 10 and 20 nm, between the nanoparticles and the emitting molecule, enabling electromagnetic coupling without fluorescence quenching.

METHODOLOGY: AgNPs were synthesized using a bottom-up approach through the chemical reduction of Ag⁺ ions with sodium borohydride (NaBH₄), yielding nanoparticles with an extinction band compatible with the absorption region of MB. Subsequently, different volumes of the AgNP suspension (10, 20, and 40 µL) were added to MB solutions, adjusting the final dye concentration to 15 µmol L⁻¹. An MB solution at the same concentration, without AgNPs, was used as a control. The samples were analyzed by spectrofluorimetry to evaluate the fluorescence behavior of MB in the absence and presence of the nanoparticles.

RESULTS AND DISCUSSION: The association of MB with AgNPs resulted in changes in fluorescence intensity. An increase of 9.0% was observed with the addition of 10 µL of AgNPs, whereas volumes of 20 and 40 µL led to smaller enhancements of 6.1% and 5.4%, respectively. These findings indicate that increasing the amount of nanoparticles does not necessarily result in greater fluorescence signal amplification.

CONCLUSION: It is concluded that fluorescence enhancement of MB is feasible under the studied conditions, with the addition of 10 µL of AgNPs being the most effective. These results highlight the potential of this system for applications in phototherapy and other photoinduced processes.

Metalenses based on optical metasurfaces enable wavefront manipulation using subwavelength nanostructures and provide a promising route toward compact and integrated optical systems. However, strong chromatic aberration caused by wavelength-dependent phase responses remains a major obstacle for practical metalens applications in the visible regime.

In this work, we present the design and analysis of an achromatic metalens operating in the visible spectrum using silicon nitride (Si₃N₄) dielectric metasurfaces. The metalens employs a phase-engineering strategy based on propagation-phase modulation of polarization-independent nanostructures. By constructing a unit-cell phase library through systematic parameter scanning, the phase responses at different wavelengths are accurately mapped. An interleaved arrangement strategy is introduced, where meta-atoms designed for different target wavelengths are alternately distributed within a single metalens aperture, enabling multi-wavelength phase compensation without increasing structural complexity.

Numerical simulations demonstrate that the proposed metalens achieves near-coincident focal positions across a broad visible wavelength range. The focal length variation is significantly suppressed compared with conventional single-wavelength metalenses. The metalens exhibits stable focusing behavior with symmetric focal spots, consistent focal sizes, and improved chromatic tolerance. The results confirm that the interleaved design effectively mitigates chromatic focal shift while maintaining high transmission efficiency.

This study provides a practical and scalable approach to achieving achromatic focusing in visible-wavelength metalenses. The proposed Si₃N₄-based interleaved design offers strong potential for compact imaging systems, integrated photonics, and visible-light optical devices.

Absorption optical spectroscopy allows measuring structural disorder and fundamental electronic properties (e.g., bandgap energy, E_g) of solid polymers by combining the interferometric and extinction information contained in UV-Vis-NIR spectra. Here, as an example, a thin polyethylene terephthalate (PET) film has been optically investigated before and after mild uniaxial/biaxial hand stretching, in order to establish the effect of such mechanical deformation on thickness, structural disorder, and bandgap energy. Thin PET films are frequently used in electronic packaging, magnetic tapes, and adhesive tape for various electronic purposes, like thermal insulators for battery, LCD and electromagnetic absorption board fixings, etc. These polymeric films typically undergo hand stretching during their use/application. The PET film thickness has been accurately calculated on the basis of the interference fringe spacing in the optical spectrum, and these values have been used for calculating the absorption coefficient and building Urbach and Tauc plots. The optical spectrum of thin PET film shows a cutoff threshold (transparent-opaque transition) at 300nm, corresponding to an E_g value of 3.96 eV. Such a transparent-opaque transition is characterized by sharp behavior (Urbach energy of 45.0 eV), which is indicative of a low structural disorder of the unstretched polymer. It has been verified that disorder and electronic structure remain practically unmodified by the slight stretching deformation (i.e., Urbach and bandgap energies do not change). Since the PET film E_g value does not depend on the deformation degree, this physical parameter can be considered as a ‘fingerprint’ of the solid polymer, thus allowing its distinction from other types of polymeric solids. Accurate E_g determination for solid polymer identification is a pivotal issue in the area of microplastics, where the required remediation/recycling approach strictly depends on plastic nature.

Widespread distribution of inexpensive CMOS image sensors has enabled researchers, including enthusiasts and educators, to create low-cost multispectral imagers for environmental studies. In this paper, we present the methods and results of some laboratory tests of a low-cost portable multispectral camera, previously designed for the monitoring of vegetation. The study was aimed at evaluating the parameters that affect the performance of the multispectral camera. The angular size of the field of view and the resulting focal length was calculated from an image of an object with known dimensions set at a predefined distance, using trigonometric relations. Depth of field and hyperfocal distance distributions were calculated from the aperture diameter and distance to the object. To test the spectral homogeneity of the field of view, parallel and uniform light from the overcast sky was directed at the sensor, and then the ratio between red and green values in the resulting image was considered. The study proposes some methods to resolve the tasks of performance assessment for a low-cost multispectral camera. The calculated total focal distance of the camera was 58 mm, and the angular size of its field of view was 3.6 degrees. The calculated depth of field ranged from 2 mm to infinity (following the definition of hyperfocal distance). Hyperfocal distance values ranged from 52.5 to 885.6 m for the smallest and the greatest aperture correspondingly. Adjustments of the optical system using the parallel daylight beam allowed us to reduce the standard deviation of the red-to-green ratio over the image down to 0.025, showing an acceptably small spectral inhomogeneity.

We report a long wave cutoff perfect absorber (LWCPA) with a nanocone array structure. Each nanocone unit comprises an InP cone grown on a SiO₂ substrate, with three layers of stacked structures nested inside: from bottom to top, these are Si₃N₄ blocks, Cr blocks, and Au cones. The structure exhibits outstanding absorption performance from ultraviolet to near-infrared wavelengths, achieving an average absorption of 97.9% in the 200–820 nm band. A sharp transition occurs as absorption drops dramatically from 95% at 820 nm to 10% at 1880 nm, with an average absorption of only 3.5% in the non-absorption band of 1880–4000 nm. Key performance metrics include an extinction ratio of 9.78 dB, an extinction difference of 85%, and a cutoff slope of 0.234 nm⁻¹. Considering that this structure may be applied to photoelectric conversion systems in the future, the present invention incorporates Si₃N₄ in advance and verifies that the absorption rate remains at a high level under its influence, thereby laying the groundwork for subsequent application of this structure in photoelectric conversion systems. The design was optimized via finite-difference time-domain (FDTD) simulations, with structural parameters such as nanocone height and base dimensions fine-tuned to enhance absorption and cutoff characteristics. This LWCPA offers an efficient strategy for ideal solar heat absorber design, with significant potential for applications in renewable energy technologies, including solar thermal photoelectric and solar thermal energy systems.