The deposition of uniform thin films is a critical process requirement in manufacturing precision optical components. Nonuniform thicknesses directly degrade device performance, creating a need for robust process control solutions. This paper presents an adaptive computational framework for the engineering and optimization of shadow masks, designed to correct deposition variations in physical vapor deposition systems over a large-aperture coating area of 20 cm in diameter. The simulation framework integrates a vector-based cosine power law for vapor distribution with a dynamic shadow projection model that couples mask geometry to the substrate's radial displacement. To ensure reliable convergence to the global minimum, a two-stage optimization strategy using the Nelder-Mead algorithm is employed to minimize thickness variance over a configurable set of monitoring points. The framework was experimentally validated by depositing MgF2 over the 20 cm target zone, achieving a final thickness uniformity of 1.02%. This represents a significant improvement over the >50% nonuniformity of the uncorrected system. The simulation accurately predicts the experimental outcome (uniformity of 0.91%), demonstrating the framework's effectiveness as a high-fidelity design-for-manufacturing tool for advanced optical coatings on extended surfaces.

Single-step Physical Vapor Deposition (PVD) using a static shadow mask offers a low-cost route to producing Gradient-Index (GRIN) optical filters; however, achieving high-fidelity, radially symmetric thickness profiles with standard off-axis evaporation sources remains a formidable inverse design challenge. In this work, we introduce a comprehensive computational framework that closes this gap by optimally engineering the mask geometry through a fully parametric representation coupled to a high-fidelity PVD simulation. The model rigorously accounts for the angular emission characteristics of the evaporation source, three-dimensional shadowing dynamics, and the substrate’s complete 360∘ rotation. A derivative-free Nelder-Mead optimization drives the inverse design, yielding a non-intuitive, highly asymmetric apodization mask that precisely compensates for system-level non-uniformities. For a 24 cm-diameter substrate with a cosine-shaped thickness profile (400 nm center, 200 nm edge), the method achieves a Root Mean Square Error of only 11.46 nm-an order-of-magnitude improvement in accuracy that is unattainable with analytical mask geometries. Functional optical simulations reveal that the resulting GRIN filter provides effective aberration correction and substantially enhances the imaging sharpness. Robustness analyzes, including studies of stochastic process noise and mask-placement tolerance, confirm the manufacturability and resilience of the design under real fabrication conditions. Together, we established a validated design-for-manufacturing paradigm that enables rapid, scalable, and high-precision fabrication of custom GRIN optics via a single-step PVD process.

We investigate the effect of iodine vapor on ionic transport in MAPbI(3) thin films using the photoelectromotive force (photo-EMF) technique. An abrupt shift in the interference pattern reveals a rapid, reversible quenching of the ionic signal upon iodine exposure. Full recovery in an inert atmosphere confirms that iodine vacancies-not interstitials-govern ion migration in ambient conditions. These insights clarify ion-related degradation mechanisms and inform defect passivation strategies for stable perovskite devices.

Humidity strongly influences ion migration in methylammonium lead iodide (MAPbI(3)) perovskite films, posing a challenge for device stability. Using photo-electromotive force (photo-EMF) measurements, we show that even minor humidity variations ( 10% RH) cause significant and reversible changes in ionic response, despite the presence of common encapsulation layers (PMMA, MgF2, SiO2). While epoxy-glass sealing blocks moisture, it distorts the film's intrinsic behavior. In contrast, paraffin-glass encapsulation effectively isolates the film from humidity without interfering with native ion dynamics, offering a reliable strategy for environmental stabilization.

The photo-EMF running grating technique revealed that multicationic perovskites exhibit superior charge transport compared to monocationic MAPI. While MAPI showed the shortest ambipolar diffusion length (0.43 +/- 0.01 mu m), CsFAMA and FAMA reached 0.58 +/- 0.04 mu m and 0.70 +/- 0.02 mu m, respectively. Temporal response analysis further indicated complex carrier dynamics, with CsFAMA and FAMA exhibiting distinct dual-relaxation behaviors. These results underscore the advantage of multication engineering for enhancing carrier transport in perovskite optoelectronics.

This work investigates the creation of nanostructured glass surfaces through the solid-state thermal dewetting of gold (Au) thin films, followed by the removal of the resulting Au nanoisland (AuNI) to form craters on the glass substrate. By varying the nominal thickness of the Au film and the annealing time, we controlled the size, density, and distribution of the AuNI, which in turn affected the dimensions of the resulting craters. Characterization of these nanostructured surfaces was performed using SEM and AFM analyses, revealing significant variations in the lateral and vertical characteristics. Experimental reflectivity measurements showed up to a 20% reduction, demonstrating the tunability of the nanostructured surfaces. The Maxwell-Garnett model (MGM) was employed to theoretically model the optical properties of these surfaces, treating the craters as air-filled cylinders. The MGM parameters, including the thickness of the nanostructured layer and the filling fraction of the cylinders, were derived to match experimental data. Further theoretical optimization indicated that achieving craters with a depth of approximately 100 nm could further reduce reflectivity. This tunability in nanostructuring enables the design of glass surfaces with specific optical properties, making the findings promising for applications such as solar cells, where minimizing Fresnel losses is crucial.

This study delves into the phenomenon of near-zero reflectance and phase singularity within a random array of gold nanoislands, employing a combination of theoretical and experimental approaches. The nanoislands are fabricated through the thermal dewetting of ultrathin gold films deposited via magnetron sputtering onto a glass substrate. Their morphology is characterized using scanning electron microscopy and atomic force microscopy. To unravel the plasmonic behavior, we conducted measurements of reflectance and phase spectra using a common-path interferometer in an attenuated total reflectance configuration. Our analysis reveals a partial state of topological darkness in the examined sample, characterized by near-zero reflection for the p polarization component. This discovery is further substantiated by the observation of phase singularity, as evidenced by abrupt +/-pi phase jumps in the differential phase spectra. Moreover, our study demonstrates the utility of measuring the phase and its derivative at resonance near the singularity for highly sensitive detection of changes in the bulk refractive index of the surrounding medium. The experimental findings are rigorously validated by comparing them with analytically calculated reflectance and phase spectra using the island film theory, yielding a good agreement.

This study provides theoretical and experimental evidence that the voltage generated in perovskite films by interference fringes' motion at low velocities can be used as a tool for assessing ions' electric mobility in these materials. We introduce a theoretical model for running fringe (RF) photo-electromotive force (EMF) in bipolar semiconductors, which considers the effects of mobile ions. This model leads to an analytical expression for the dispersion relation of space charge waves in the presence of mobile ions. Notably, it predicts a peak in the RF photo-EMF voltage when the velocity of fringe displacement matches the ion velocity in the photo-induced space charge field. To validate this, we conducted RF photo-EMF measurements on thin films of the methylammonium lead iodide semiconductor. The observed experimental dependencies align closely with theoretical predictions, and the determined values of ions' electric mobilities and activation energies are consistent with those previously reported in the literature.

In this study, we investigate the phenomenon of nearly zero reflectance and associated phase singularity in a random array of gold nanoislands (Au NI) both theoretically and experimentally. The Au NI were produced via solid-state thermal dewetting of ultrathin gold films, which were magnetron sputtered onto a glass substrate. The morphology of the nanoislands was characterized using scanning electron microscopy and atomic force microscopy. To understand the plasmonic response of the random array of Au NI, we conducted reflectance measurements for both s and p polarized beams demonstrating the p. These measurements were performed using the attenuated total internal reflectance configuration. A partial state of topological darkness in a random array of Au NI was demonstrated by showing nearly zero reflection for the p polarization component. Additionally, we employed a common path spectral interferometer to measure the differential phase spectra. Our findings revealed that the differential phase spectra exhibited abrupt ±π phase jumps, indicating the presence of a phase singularity regime. Moreover, we demonstrated high bulk reflectance index sensitivity (RIS) within this regime. To validate our experimental results, we compared them with analytical reflectance and phase spectra obtained through the application of island film theory. The agreement between the experimental and theoretical predictions provided strong confirmation of our measurement technique.

We have demonstrated theoretically and experimentally that the current induced by an interference pattern moving at constant velocity can be used to determine the ion mobility and activation energy in perovskite semiconductors. The frequency dependence of the signal has features predicted by theory: the high-frequency peak corresponds to the electron/hole photoconductivity relaxation process, and the low-frequency peak occurs when the velocity of the interference pattern synchronizes with the ion motion; by determining the peak’s position, it becomes possible to estimate the ion mobility. The values of ion mobility and activation energy agree with the data reported in the literature.

In this work, we investigate the plasmonic response of a random metasurface based on gold nano-islands (AuNI) in an attenuated total reflectance (ATR) configuration. AuNI structures were obtained by thermal annealing of an ultrathin gold film deposited on a glass substrate. The samples exhibited a wide range of sizes and particle densities, varying the nominal gold thickness. For p polarization, a well-defined localized surface plasmon resonance (LSPR) dip was observed in all samples, while for s polarization, only AuNI with the smallest radii showed this dip. Some samples exhibited nearly zero reflection at the resonance wavelength. The highest sensitivity among all tested samples was achieved in these samples, providing potential for optimizing LSPR transducers in sensing applications. Notably, the resonance wavelength exhibited a nonlinear dependence on the refractive index in sensitivity measurements displaying a blue shift.

This study aims to contribute to the development of theoretical and experimental tools for characterizing the transport properties of perovskite semiconductors. In the context of existing transport characterization methods for perovskites, there is a need for techniques that can accurately assess the critical transport parameters, such as diffusion lengths, given the specific challenges posed, such as their inherent instabilities. The novel methodology employed involves the development of a theoretical model to describe the running fringes-induced photo-electromotive force (RF photo-EMF) effect in bipolar photoconductors with a rather general type of photoconductivity relaxation behaviors for both carriers. This model is founded on the theory of photoinduced space charge grating formation in semiconductors. Subsequently, RF photo-EMF experiments were conducted on methylammonium lead iodide (CH 3NH 3PbI 3 or MAPI) polycrystalline films of varying grain sizes. By utilizing the RF photo-EMF technique, we successfully elucidated crucial transport and recombination characteristics, notably the ambipolar diffusion length and relaxation times of the charge carriers. Significantly, the developed theoretical model exhibited a remarkable agreement with the experimental results, highlighting its ability in explaining and predicting the behavior of charge carriers in perovskite semiconductors. The results of this study make a substantial contribution to the field of perovskite semiconductors by offering a novel theoretical and experimental approach to characterization of perovskites' transport properties.

The goal of this work is to study the effect of annealing temperature T a on the properties of CH 3 NH 3 PbI 3 (MAPI) thin films deposited on glass substrate through structural, compositional, and optical characterization. The films were obtained by one-step deposition method in which an anti-solvent drip was implemented with some delay during spin coating of the precursor mixture, followed by thermal annealing to promote solvent evaporation and rapid crystallization of the film. Properties of the perovskite film after thermal annealing were characterized by different analytical methods. The morphology and roughness of the films were studied by scanning electron microscopy and atomic force microscopy. The crystalline phase was characterized by X-ray diffraction. The optical properties were also determined by UV–Vis spectroscopy. Finally, the elemental composition was analyzed by secondary ion mass spectroscopy. In the temperature range of 100–160 °C, variable average grain diameters between ~ 200 and ~ 500 nm were obtained. However, higher post-deposition thermal annealing temperatures produce clusters of PbI 2 between CH 3 NH 3 PbI 3 grain boundaries. XRD measurements showed a decrease in MAPI crystallite size and an increase in PbI 2 crystallite size and amount with increasing annealing temperature. In addition, higher T a results in a modification of the absorption/reflectance spectra and a red shift of an optical band gap. The results of this study can be useful to produce thin films of MAPI with tunable optical and electronic properties for optimizing the performance of photovoltaic devices.

In this work, we have developed a refractive index change sensing system utilizing localized surface plasmon resonance (LSPR) transduction, combined with a position-sensitive photodetector (PSPD). As the transducers, we utilized gold nano-islands formed through thermal annealing of an Au film with a nominal thickness of 13 nm. The LSPR was excited by evanescent wave in an attenuated total reflectance configuration. Refractive index changes result in modifications across the angular spectrum of LSPR, giving rise to variations in the differential signal detected between the two quadrants of the photodetector. We determined the refractive index resolution of our sensing system at different wavelengths and performed a comparative analysis with traditional surface plasmon resonance (SPR) transducers and available literature data. While LSPR transducers demonstrate a lower refractive index resolution (RIR) compared to SPR, the approach presented in this work stands out when compared to other LSPR sensing methods. Notably, at a wavelength of 785 nm, it achieves a remarkable RIR of 1.4 × 10−6 RIU.

We present results of theoretical and experimental study of photo-EMF induced by running grating in perovskite thin films, parameters such as electron and hole photoconductivity relaxation time, ambipolar diffusion length, minority carriers drift mobility are obtained.

We investigate analytically and numerically the linear stability of coherent-solitonic states of the Gross-Pitaevskii equation with parabolic potential. The two lowest-order states are linearly stable. For small enough nonlinearity, either positive or negative, higher states with low intensity develop a limited number of unstable perturbation modes. When the state intensity is raised above a threshold, its stabilization occurs. The full numerical solution of the Gross-Pitaevskii equation confirms that the linear analysis gives an adequate description of solution stability properties for low-order states and moderate propagation lengths.

The detection scheme based on phase detection of SPR response was developed. We show that the proposed biosensing scheme can detect SARS-CoV-2 genetic material with high specificity, low detection limit and short detection time.

This study demonstrated the capabilities of method which uses the steepness of the localized surface plasmon resonance phase response for sensing of molecular binding event.

This work presents the results of experimental and theoretical study of the sensing characteristics of disordered arrays of gold nanoisland (Au NI) on top of glass substrate. The influence of the Au NI array parameters (average NI size and fill factor) on bulk refractive index sensitivity was analyzed.