In many industrial applications, military technology, and biomedical fields, coherent diffraction imaging technology has gradually replaced classical camera imaging methods. Coherent diffraction imaging extends the Ptychographic Iterative Engine (PIE) technique, which provides a large field of view in addition to high-resolution imaging. However, in the actual imaging process, there are many kinds of noise with different intensities and distributions in the reconstructed image due to the mechanism of PIE and imaging equipment. These noises will not only slow down the imaging speed and reduce the imaging quality, but also lead to the failure of direct image reconstruction. In this paper, an adaptive iterative guided filtering algorithm is proposed based on PIE reconstruction characteristics. By introducing a filter control factor into the PIE reconstruction algorithm, the intensity of the filter will gradually increase with PIE iteration. The edge-preserving property of the guided filter can protect the details well. According to the TOG evaluation function, compared with unfiltered PIE reconstruction, the method increased by 0.625, and the image quality improved by 50%. Compared with other image filtering functions, the TOG of reconstructed images increased by 20%. In terms of operation efficiency, this method increases the operation time by less than 10%, and its efficiency is higher than other filtering algorithms under the same iteration times.

Photon scattering-induced wavefront aberrations impose significant limitations on optical imaging within scattering media, particularly in environments characterized by diffusion. Scattering imaging techniques leveraging memory effects offer a promising avenue for imaging under the regime of multiple scattering. Nonetheless, the presence of interference phase traps inherent to scattered light often results in failures and distortion. We propose an algorithm for computational imaging to address the challenges. By employing gradient-based calculations to delineate the phase distribution of photon ensembles amidst diffuse scattering, we preemptively assess the convergence or divergence of the state of the retrieval algorithm prior to recovery. This proactive strategy serves to circumvent disruptions caused by interference traps, expediting the identification of the accurate state from a myriad of stochastic photon projections, thereby facilitating rapid and high-fidelity scattering retrieval. Through rigorous experimentation involving dozen-group targets and each group with 100 repeated trials, we quantitatively evaluate the proposed method. Our research demonstrates a substantial enhancement in success rates, approximately 3 times higher than those without interference mitigation, while achieving a reduction in computational time, down to 0.2 of the original. This approach introduces a novel scattering imaging technique, 'achieving more with less,' offering technical support for dynamic video imaging in intricate scattering environments such as biological tissues and atmospheric conditions.

Single-crystal hybrid perovskites (SC-HP) stand out as prominent materials in the family of next-generation semiconductors, owing to their outstanding properties, including tunable bandgaps, high absorption coefficients, excellent photophysical properties, intense luminescence, and their low-cost solution-based processability ^{[1, 2]}. Compared to their polycrystalline counterparts, single-crystal perovskites exhibit longer carrier lifetimes and diffusion lengths, lower trap state density, and enhanced environmental stability ^[3,4]. Two-dimensional SC-HP are especially interesting as their long-range ordered multiple quantum well structure induces additional properties such as large excitonic effects.

In this work, we present the progress in the growth of single crystal hybrid perovskites using the space-confined approach. We then investigate the structural properties, morphology, and optoelectronic behavior of 2D thin film of PEA₂PbI₄ single-crystals grown with this technique. We fabricate a planar photodetector and study its spectral photoresponse as a function of temperature and wavelength and its stability under environmental conditions.

The results demonstrate the synthesis of high-quality single crystalline materials, displaying low defect density and suppressed bias induced ion migration, and provide advancement in the comprehension of photodetection mechanisms in this material.

[1] Simbula, A. et al. Nat Commun 2023, 14, 4125.
[2] Simbula A, Demontis V et al. ACS Omega 2024, 9, 36865−36873.
[3] Liu, Y. et al. Nat Commun 2018, 9, 5302.
[4] Gao, X. et al. Advanced Science 2019,6,1900941.

This paper describes the development and evaluation of an ultra-sensitive modified circular photonic crystal fibre (MC-PCF) sensor for efficient alcohol detection. Operating at 850 nm, the sensor has exceptional relative sensitivity and low confinement losses, making it suitable for a wide range of practical applications. The MC-PCF sensor was developed using Comsol Multiphysics and a finite element method to improve light--matter interaction by increasing sensitivity and precision. Performance metrics such as relative sensitivity, confinement loss, and nonlinear coefficients were assessed for various alcohols (methanol, ethanol, propanol, butanol, and pentanol). The sensor has impressive relative sensitivity values: 95.51% for methanol, 97.2% for ethanol, 97.85% for propanol, 98.69% for butanol, and 99.4% for pentanol. The confinement losses are 2.345×10⁻⁹, 1.022×10⁻⁹, 8.656×10⁻¹⁰, 1.821×10⁻⁹, and 3.097×10⁻⁹ dB/m, respectively. Methanol, ethanol, propanol, butanol, and pentanol have nonlinear coefficients of 78.95, 75, 73.69, 73.03, and 72.54 W⁻¹km⁻¹, respectively. The numerical apertures for the MC-PCF sensor at an 850 nm operating wavelength are 0.2599 for methanol, 0.2566 for ethanol, and 0.2567 for propanol, butanol, and pentanol. The optimized design of the MC-PCF sensor significantly improves light--matter interaction, resulting in high precision and rapid response when detecting changes in alcohol concentration. This makes the proposed sensor a strong and dependable solution for industrial quality control, medical diagnostics, and environmental monitoring. In summary, the MC-PCF sensor's outstanding sensitivity and low confinement loss at the near-infrared region demonstrate its potential for effective alcohol detection across various fields.

The spectroscopic properties of Ni²⁺ ions are particularly intriguing due to their emission in the near-infrared (NIR) range, which enables various potential applications [1]. One notable potential application of the luminescence of Ni²⁺ ions is pressure sensing, due to the dependence of the energy of the ³T₂_g level on the strength of the crystal field, which is altered by pressure-induced changes in the metal--oxygen distances [2]. Consequently, applying pressure should affect the spectroscopic properties of Ni²⁺ ions. To explore the potential of Ni²⁺ ions as luminescent manometers, we investigated the luminescence of Ni²⁺ ions in doped spinel-type gallate under applied hydrostatic pressure. The change in energy of the ³T₂_g excited state of Ni²⁺ caused by the change in crystal field strength resulted in a significant spectral shift of the emission band associated with the ³T₂_g→³A₂_g electronic transition of Ni²⁺ ions, exceeding 10 nm GPa⁻¹. Based on this substantial shift, we proposed a ratiometric readout mode using the luminescence intensity ratio (LIR), defined by integrated two spectral ranges of the broad emission band of Ni²⁺ ions. This approach, which is uncommon for luminescence manometry, offers exceptional high-pressure sensitivity of more than 50% GPa⁻¹, while also ensuring temperature-independent pressure readouts. Our results demonstrate the significant potential of both the ratiometric approach and the utilization of Ni²⁺ ions for optical pressure sensing applications.

Acknowledgement: This work was supported by the National Science Center Poland (NCN) under project No. 2023/49/N/ST5/01020.

[1] C. Matuszewska et al., Journal of Luminescence 2020, 223, 117221

[2] M.G. Brik et al., Journal of Luminescence 2014, 148, 338-341

Carbon Dots (CDs), a fluorescent carbon-based nanomaterial, can be seen as more appealing than molecular fluorophores and metallic nanoparticles due to their properties. These include good water solubility, biocompatibility, high stability, low toxicity, adjustable fluorescence, and easy surface functionalization. These features have led to their increasing use in fields such as sensing, bioimaging, and photocatalysis, among others. In fact, CDs' unique photoluminescence properties show promising potential for sensing applications. CDs have been shown to serve as sensing receptors in nanoprobes, in which their features can be used as a sensing signal. Metal cations, non-metal ions, solvents, pesticides, and organic compounds are examples of analytes for which CDs can be used as sensors.

Relevantly, CDs can be produced from different carbon sources, including various types of organic waste. Thus, CDs could contribute toward a circular economy and upcycling waste. However, waste-based CDs usually have a low fluorescence quantum yield (QY_FL<20%), which limits their practical applications (especially in sensing).

Herein, we developed a hydrothermal synthesis strategy for CDs that employs different organic wastes as carbon precursors and consistently generates CDs with appreciable fluorescence. This strategy was validated by testing different types of waste: corn stover—CD@CS; coffee—CD@C; sawdust—CD@S; and cork—CD@CK. These CDs present similar fluorescence profiles, with emission and excitation maximums at ~440 and ~350 nm, respectively. More importantly, the QY_FL of these CDs presents significant values (CD@CS: 39.3%; CD@C: 24.6%; CD@S: 35.9%; CD@CK: 21.8%). So, we obtained CDs from different waste materials without compromising their performance in terms of QY_FL, which is essential for their future use in sensing applications.

Acknowledgments
“Fundação para a Ciência e Tecnologia” (FCT, Portugal) is acknowledged for the funding of R&D Units CIQUP (UIDB/00081/2020) and Associated Laboratory IMS (LA/P/0056/2020). Sónia Fernandes also acknowledges the FCT for funding her Ph.D. grant (2021.05479.BD).

Introduction: Condensed borates are compounds constructed of three-dimensional lattices of borate groups BO₃ and BO₄. They can form amorphous materials (glasses), ordered matrices (crystals), or a mixture of the two (glass–ceramics). They are characterized by high stiffness, which yields a high emission efficiency and stability of the luminescence against host modifications. Divalent tin (Sn²⁺) is a ns²-type luminescent center, which has found use in the fabrication of phosphors and scintillating materials. Sn²⁺ can be excited in UV and exhibits a very wide emission band, spanning the whole visible range. The position of the excitation and emission maxima depend on the host material to some degree.

Methods: This study comprises an extended investigation into the luminescence of the divalent tin (Sn²⁺) in condensed borates. The studied condensed borate systems include 25 MgO–12.5 La₂O₃– 62.5 B₂O₃ (LaMgB₅O₁₀), labeled as LaMBO, which can be obtained in both a crystalline and an amorphous form. It can also form a glass–ceramic through the process of isochemical crystallization. The amorphous and crystalline samples of condensed borates were investigated and their structure, optical properties and luminescence were evaluated. Emission and excitation spectra, as well as decay times and quantum yield, were recorded.

Results: The results indicate that Sn²⁺ can exhibit a range of luminescence in the studied hosts, ranging from a blueish, cool white emission to red-tinted, warm white emission. The correlated color temperature (CCT) of the emission can be tuned using an excitation light of different wavelengths in the UV spectral range or by using two-wavelength excitation. The samples exhibit a high color rendering index (CRI) of >95 in the relevant CCT range and a high quantum yield >80%.

Conclusions: The condensed borate materials, doped with divalent tin, are promising materials for novel, efficient, dual-excitation phosphors for high CRI wLED with tunable CCT. Further insight into the structure of condense borate glass–ceramics can provide interesting fields of applications.

Laser direct writing offers precise material treatment with minimal thermal damage, crucial for controlled energy application, beam-material interaction, and heat penetration. Traditional methods for large-area graphene growth, such as chemical vapor deposition (CVD), typically require metallic precursors like Cu and Ni. However, recent advancements have demonstrated the potential for non-metallic precursors. Notably, Rice University showed that CO2 laser irradiation could convert polyimide (PI) and polyetherimide (PEI) into graphene. In this study, we present a laser direct writing technique for forming graphene patterns on polybenzimidazole (PBI) thin films and glass substrates using a low-cost nanosecond UV laser system. This method avoids thermal damage to substrates and eliminates the need for metallic precursors. The UV laser induces photochemical reactions, breaking molecular bonds to form graphene without harming the substrate.

The methodology involves dissolving PBI in dimethylacetamide (DMAC) to create a solution, which is then coated on glass sheets. After drying the coated glass, a nanosecond UV laser is used to treat the PBI-coated sheet, forming flaky silver-black graphene. Optimal laser conditions include a wavelength of 355 nm, a pulse duration of 100 ns, a frequency of 50 kHz, and a scanning speed of 20 mm/s. A Q factor of around 16.4 yields the best results, producing graphene with a resistance of approximately 50Ω over 2 mm.

Raman spectroscopy confirms the graphene formation, indicated by the characteristic 2D peak and the D/G peak ratio, which reflects the degree of carbon crystallization and defect ratio.

In conclusion, this cost-effective nanosecond UV laser technique offers a scalable approach to graphene production on PBI films and glass substrates, presenting a significant advancement in non-thermal, metal-free graphene fabrication.

Metal halide perovskites have garnered significant attention over the years as they exhibit a diverse range of properties, making them key materials for numerous applications across various industrial fields, from catalysts and piezoelectrics to optics materials, scintillators and solar cells. Of particular interest is the use of halide perovskites as matrices for upconversion, which involves the interaction of low-energy light photons with matter, resulting in high-energy luminescent emission. A high-priority task is the search for new phosphors that efficiently convert visible light into ultraviolet (UV) radiation. Ultraviolet light initiates photochemical reactions that damage or destroy DNA and RNA in cells and viruses, making it effective for surface disinfection, wastewater treatment and cancer phototherapy [1]. The most damaging type of UV radiation is UVC (100-280 nm).

This paper presents for the first time an investigation of visible-to-UVC upconversion luminescence in Pr³⁺-doped fluoroperovskite crystallites. The upconversion properties of these crystallites are compared with those of LiYF₄:Pr³⁺ phosphor. In addition, luminescent properties in the visible range will be presented.

ACKNOWLEDGEMENTS

This work was supported by The National Science Centre (NCN) under the OPUS 21 project, grant no. UMO-2021/41/B/ST5/03792, which is gratefully acknowledged. One of the authors (Oleksandr Gryppa) is thankful to Visegrad Fellowship #62410067.

[1] Minamikawa, T.; Koma, T.; Suzuki, A. et al. Quantitative Evaluation of SARS-CoV-2 Inactivation Using a Deep Ultraviolet Light-Emitting Diode. Sci. Rep. 2021, 11, 5070.

Machine vision is extensively utilized in diverse fields such as target detection and dimension measurement due to its inherent characteristics of high speed, precision, safety, and reliability, facilitating enhanced operational efficiency and quality assurance. However, influenced by factors such as processing technology and assembly techniques, non-uniform brightness and optical distortion significantly impact visual measurement results. To solve this issue, we propose a camera distortion correction method based on brightness non-uniformity compensation. This method preprocesses vignetted images using an improved simulated annealing algorithm with image entropy, processes the phase-shift and checkerboard patterns captured by the camera to obtain the intrinsic and extrinsic parameters of the camera, and corrects the distorted images. The proposed method significantly improves camera calibration accuracy and image rectification effectiveness compared to traditional camera calibration methods through advanced image preprocessing techniques. The experimental results demonstrate that after brightness non-uniformity correction, the error can be reduced by more than 80%. Using geometric distortion as an evaluation criterion, our method achieves an accuracy improvement of over 25% compared to Zhang’s algorithm. It exhibits versatility across domains including camera calibration, target identification, and detection, thereby augmenting the precision and efficiency of visual assessments. By implementing our proposed approach, advancements can be made in the refinement of visual measurement techniques, bolstering the reliability and efficacy of data analysis in fields reliant on visual data processing.