Sign in to use this feature.

Years

Between: -

Subjects

remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline

Journals

Article Types

Countries / Regions

remove_circle_outline
remove_circle_outline
remove_circle_outline

Search Results (359)

Search Parameters:
Keywords = optical harmonic generation

Order results
Result details
Results per page
Select all
Export citation of selected articles as:
18 pages, 12019 KiB  
Article
Influence of Temperature on the Optical Properties of Ternary Organic Thin Films for Photovoltaics
by Gabriela Lewinska, Jerzy Sanetra, Konstanty W. Marszalek, Alexander Quandt and Bouchta Sahraoui
Materials 2025, 18(14), 3319; https://doi.org/10.3390/ma18143319 - 15 Jul 2025
Viewed by 296
Abstract
This study investigates the influence of temperature on the linear and nonlinear optical properties of ternary organic thin films for solar cell applications. Three-component organic thin films (poly({4,8-bis[(2-ethylhexyl)oxy]benzo [1,2-b:4,5-b′]dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl] thieno[3,4-b]thiophenediyl}) and (poly([2,6′-4,8-di(5-ethylhexylthienyl)benzo[1,2-b;3,3-b]dithiophene]{3-fluoro-2[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}), marked PTB7 and PTB7th- donors, PCBM, phenyl-C61-butyric acid methyl ester acceptor, [...] Read more.
This study investigates the influence of temperature on the linear and nonlinear optical properties of ternary organic thin films for solar cell applications. Three-component organic thin films (poly({4,8-bis[(2-ethylhexyl)oxy]benzo [1,2-b:4,5-b′]dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl] thieno[3,4-b]thiophenediyl}) and (poly([2,6′-4,8-di(5-ethylhexylthienyl)benzo[1,2-b;3,3-b]dithiophene]{3-fluoro-2[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}), marked PTB7 and PTB7th- donors, PCBM, phenyl-C61-butyric acid methyl ester acceptor, and Y5: 2,2′-((2Z,2′Z)-((12,13-bis(2-ethylhexyl)-3,9-diundecyl-12,13-dihydro[1,2,5]thiadiazolo[3,4e]thieno[2′,3′:4′,5′] thieno[2′,3′:4,5]pyrrolo[3,2-g] thieno[2′,3′:4,5]thieno[3,2-b]indole-2,10-diyl)bis(methanylylidene))bis(3-oxo-2,3-dihydro1H-indene-2,1-diylidene))dimalononitrile) and Y6 non-fullerene acceptors: (2,2′-((2Z,2′Z)-((12,13-bis(2-ethylhexyl)-3,9-diundecyl-12,13- dihydro-[1,2,5]thiadiazolo[3,4- e] thieno [2,″3″:4′,5′]thieno [2′,3′:4,5]), non-fullerene acceptors, were analyzed using spectroscopic ellipsometry and third-harmonic generation techniques across a temperature range of 30 °C to 120 °C. The absorption spectra of the ternary layers remained largely stable with temperature, but ellipsometry revealed temperature-dependent changes in layer thickness (a few percent increase during heating) and variations in refractive index and extinction coefficients, suggesting modest structural alterations. Analysis using a gradient model indicated that film composition varies with thickness. Third-harmonic generation measurements showed a decrease in χ(3) after annealing, with the most significant change observed in the PTB7th:Y5:PCBM layer. Full article
Show Figures

Figure 1

9 pages, 2121 KiB  
Article
Using Second-Harmonic Generation Microscopy Images of Bee Honey Crystals to Detect Fructose Adulteration
by Manuel H. De la Torre-I, J. M. Flores-Moreno, C. Frausto-Reyes and Rafael Casillas-Peñuelas
Crystals 2025, 15(7), 634; https://doi.org/10.3390/cryst15070634 - 10 Jul 2025
Viewed by 275
Abstract
Second-harmonic generation microscopy is applied to mesquite honey samples with different fructose adulteration concentrations. As a proof of principle, mesquite honey is selected for this test, as it has a monofloral and spreadable-like-butter consistency, besides its economic relevance in the central region of [...] Read more.
Second-harmonic generation microscopy is applied to mesquite honey samples with different fructose adulteration concentrations. As a proof of principle, mesquite honey is selected for this test, as it has a monofloral and spreadable-like-butter consistency, besides its economic relevance in the central region of Mexico. Second-harmonic generation microscopy is an optical method that images microstructures, such as sugar crystals in bee honey, without the interference of the liquid phase. Each recorded image is spectrally registered using the photomultiplier detector of the microscope, resulting in several gray-level histograms that are numerically analyzed using signal and image processing techniques. Several samples are prepared, adulterated, and analyzed for this purpose. The inspection requires only a microscopic amount of honey, making it a suitable technique for rare and exotic honey samples that are harvested in limited quantities. The analysis of the experimental results reveals that the second-harmonic generation microscopy signal is sensitive to liquid fructose adulteration in honey, with its signal decreasing as the amount of added fructose increases. Full article
(This article belongs to the Section Industrial Crystallization)
Show Figures

Figure 1

11 pages, 2180 KiB  
Article
Impact of Mild Acid and Alkali Treatments on Cotton Fibers with Nonlinear Optical Imaging and SEM Analysis
by Huipeng Gao, Xiaoxiao Li, Rui Li, Chao Wang, Hsiang-Chen Chui and Quan Zhang
Photonics 2025, 12(7), 688; https://doi.org/10.3390/photonics12070688 - 8 Jul 2025
Viewed by 261
Abstract
This study investigates the structural effects of dilute acid and alkali treatments on cotton fibers, aiming to understand the influence of chemical pretreatment on cellulose morphology. Cotton samples were exposed to 1% sulfuric acid and 1% sodium hydroxide at 90 °C, and the [...] Read more.
This study investigates the structural effects of dilute acid and alkali treatments on cotton fibers, aiming to understand the influence of chemical pretreatment on cellulose morphology. Cotton samples were exposed to 1% sulfuric acid and 1% sodium hydroxide at 90 °C, and the resulting changes were evaluated using scanning electron microscopy and nonlinear optical imaging techniques. The results indicate that sulfuric acid causes significant fiber degradation, leading to fragmentation and reduced fiber thickness. In contrast, sodium hydroxide treatment results in a roughened, flaky surface while preserving the overall structural integrity, with fibers appearing fluffier and more accessible to enzymatic processes. Untreated cotton fibers maintained a smooth and uniform surface, confirming the chemical specificity of the observed changes. These findings are crucial for optimizing biomass pretreatment methods, demonstrating that dilute chemical treatments primarily affect macrostructural features without significantly disrupting the cellulose microfibrils. The study provides valuable insights for the development of efficient biorefining processes and sustainable bio-based materials, highlighting the importance of selecting appropriate chemical conditions to enhance enzymatic hydrolysis and biomass conversion while maintaining the core structure of cellulose. This research contributes to advancing the understanding of cellulose’s structural resilience under mild chemical pretreatment conditions. Full article
(This article belongs to the Section Optical Interaction Science)
Show Figures

Figure 1

9 pages, 1553 KiB  
Communication
Orthogonally Polarized Pr:LLF Red Laser at 698 nm with Tunable Power Ratio
by Haotian Huang, Menghan Jia, Yuzhao Li, Jing Xia, Nguyentuan Anh and Yanfei Lü
Photonics 2025, 12(7), 666; https://doi.org/10.3390/photonics12070666 - 1 Jul 2025
Viewed by 168
Abstract
A continuous-wave (CW) orthogonally polarized single-wavelength red laser (OPSRL) at 698 nm with a tunable power ratio within a wide range between the two polarized components was demonstrated using two Pr3+:LiLuF4 (Pr:LLF) crystals for the first time. Through control of [...] Read more.
A continuous-wave (CW) orthogonally polarized single-wavelength red laser (OPSRL) at 698 nm with a tunable power ratio within a wide range between the two polarized components was demonstrated using two Pr3+:LiLuF4 (Pr:LLF) crystals for the first time. Through control of the waist location of the pump beam in the active media, the output power ratio of the two polarized components of the OPSRL could be adjusted. Under pumping by a 20 W, 444 nm InGaN laser diode (LD), a maximum total output power of 4.12 W was achieved with equal powers for both polarized components, corresponding to an optical conversion efficiency of 23.8% relative to the absorbed pump power. Moreover, by a type-II critical phase-matched (CPM) BBO crystal, a CW ultraviolet (UV) second-harmonic generation (SHG) at 349 nm was also obtained with a maximum output power of 723 mW. OPSRLs can penetrate deep tissues and demonstrate polarization-controlled interactions, and are used in bio-sensing and industrial cutting with minimal thermal distortion, etc. The dual-polarized capability of OPSRLs also supports multi-channel imaging and high-speed interferometry. Full article
(This article belongs to the Section Lasers, Light Sources and Sensors)
Show Figures

Figure 1

13 pages, 3840 KiB  
Article
Second Harmonic Generation Imaging of Strain-Induced Domain Evolution Across Grain Boundaries in SrTiO3 Bicrystals
by Yuhang Ren and Piyali Maity
Surfaces 2025, 8(3), 47; https://doi.org/10.3390/surfaces8030047 - 1 Jul 2025
Viewed by 310
Abstract
Understanding strain behavior near grain boundaries is critical for controlling structural distortions and oxygen vacancy migration in perovskite oxides. However, conventional techniques often lack the spatial resolution needed to analyze phase and domain evolution at the nanoscale. In this paper, polarization-dependent second-harmonic generation [...] Read more.
Understanding strain behavior near grain boundaries is critical for controlling structural distortions and oxygen vacancy migration in perovskite oxides. However, conventional techniques often lack the spatial resolution needed to analyze phase and domain evolution at the nanoscale. In this paper, polarization-dependent second-harmonic generation (SHG) imaging is employed as a tool to probe local symmetry breaking and complex domain structures in the vicinity of a low-angle grain boundary of SrTiO3 (STO) bicrystals. We show that the anisotropic strain introduced by a tilted grain boundary produces strong local distortions, leading to the coexistence of tetragonal and rhombohedral domains. By analyzing SHG intensity and variations in the second-order nonlinear optical susceptibility, we map the distribution of strain fields and domain configurations near the boundary. In pristine samples, the grain boundary acts as a localized source of strain accumulation and symmetry breaking, while in samples subjected to intentional electrical stressing, the SHG response becomes broader and more uniform, suggesting strain relaxation. This work highlights SHG imaging as a powerful technique for visualizing grain-boundary-driven structural changes, with broad implications for the design of strain-engineered functional oxide devices. Full article
(This article belongs to the Collection Featured Articles for Surfaces)
Show Figures

Figure 1

29 pages, 3391 KiB  
Article
Near-Infrared and Sono-Enhanced Photodynamic Therapy of Prostate Cancer Cells Using Phyto-Second Harmonic Generation Nanoconjugates
by Efrat Hochma, Michael A. Firer and Refael Minnes
Polymers 2025, 17(13), 1831; https://doi.org/10.3390/polym17131831 - 30 Jun 2025
Viewed by 353
Abstract
This study investigates near-infrared (NIR)-induced, Phyto-enhanced, second harmonic generation-mediated photodynamic therapy (Phyto-SHG-PDT) using barium titanate (BT)/rhein/polyethylene glycol 100 (PEG100) and BT/Yemenite “Etrog” leaf extract/PEG100 nanoconjugates. We compare continuous-wave (CW), multi-line Argon-ion laser illumination in the NIR range with high-peak-power femtosecond (fs) 800 nm [...] Read more.
This study investigates near-infrared (NIR)-induced, Phyto-enhanced, second harmonic generation-mediated photodynamic therapy (Phyto-SHG-PDT) using barium titanate (BT)/rhein/polyethylene glycol 100 (PEG100) and BT/Yemenite “Etrog” leaf extract/PEG100 nanoconjugates. We compare continuous-wave (CW), multi-line Argon-ion laser illumination in the NIR range with high-peak-power femtosecond (fs) 800 nm pulses. Under CW NIR light, BT/rhein nanoconjugates reduced PC3 prostate cancer cell viability by 18% versus non-irradiated controls (p < 0.05), while BT/extract nanoconjugates exhibited 15% dark toxicity. The observed SHG signal matched theoretical predictions and previous CW laser studies. Reactive Oxygen Species (ROS) scavenger 1,3-diphenyl-isobenzofuran (DPBF) showed reduced absorbance at 410 nm upon NIR illumination, indirectly supporting SHG emission at 400 nm from nanoconjugates. Under fs-pulsed laser exposure, pronounced two-photon absorption (TPA) and SHG effects were observed in both nanoconjugate types. Our results demonstrate the effectiveness of BT/rhein nanoconjugates under both laser conditions, while the BT/extract nanoconjugates benefited from high-power pulsed excitation. These results highlight the potential of BT-based Phyto-SHG-PDT nanoconjugates for NIR and blue light applications, leveraging nonlinear optical effects for advanced photochemical cancer therapies. Full article
Show Figures

Graphical abstract

20 pages, 4172 KiB  
Article
Multi-Level Feature Fusion Attention Generative Adversarial Network for Retinal Optical Coherence Tomography Image Denoising
by Yiming Qian and Yichao Meng
Appl. Sci. 2025, 15(12), 6697; https://doi.org/10.3390/app15126697 - 14 Jun 2025
Viewed by 454
Abstract
Background: Optical coherence tomography (OCT) is limited by inherent speckle noise, degrading retinal microarchitecture visualization and pathological analysis. Existing denoising methods inadequately balance noise suppression and structural preservation, necessitating advanced solutions for clinical OCT reconstruction. Methods: We propose MFFA-GAN, a generative adversarial [...] Read more.
Background: Optical coherence tomography (OCT) is limited by inherent speckle noise, degrading retinal microarchitecture visualization and pathological analysis. Existing denoising methods inadequately balance noise suppression and structural preservation, necessitating advanced solutions for clinical OCT reconstruction. Methods: We propose MFFA-GAN, a generative adversarial network integrating multilevel feature fusion and an efficient local attention (ELA) mechanism. It optimizes cross-feature interactions and channel-wise information flow. Evaluations on three public OCT datasets compared traditional methods and deep learning models using PSNR, SSIM, CNR, and ENL metrics. Results: MFFA-GAN achieved good performance (PSNR:30.107 dB, SSIM:0.727, CNR:3.927, ENL:529.161) on smaller datasets, outperforming benchmarks and further enhanced interpretability through pixel error maps. It preserved retinal layers and textures while suppressing noise. Ablation studies confirmed the synergy of multilevel features and ELA, improving PSNR by 1.8 dB and SSIM by 0.12 versus baselines. Conclusions: MFFA-GAN offers a reliable OCT denoising solution by harmonizing noise reduction and structural fidelity. Its hybrid attention mechanism enhances clinical image quality, aiding retinal analysis and diagnosis. Full article
(This article belongs to the Special Issue Explainable Artificial Intelligence Technology and Its Applications)
Show Figures

Figure 1

16 pages, 4359 KiB  
Article
Nonlinear Imaging Detection of Organ Fibrosis in Minute Samples for Early Stage Utilizing Dual-Channel Two-Photon and Second-Harmonic Excitation
by Bo-Song Yu, Qing-Di Cheng, Yi-Zhou Liu, Rui Zhang, Da-Wei Li, Ai-Min Wang, Li-Shuang Feng and Xiao Jia
Biosensors 2025, 15(6), 357; https://doi.org/10.3390/bios15060357 - 4 Jun 2025
Viewed by 2735
Abstract
Histopathological staining remains the fibrosis diagnostic gold standard yet suffers from staining artifacts and variability. Nonlinear optical techniques (e.g., spontaneous fluorescence, Second Harmonic Generation) enhance accuracy but struggle with rapid trace-level detection of fibrosis. To address these limitations, a dual-channel nonlinear optical imaging [...] Read more.
Histopathological staining remains the fibrosis diagnostic gold standard yet suffers from staining artifacts and variability. Nonlinear optical techniques (e.g., spontaneous fluorescence, Second Harmonic Generation) enhance accuracy but struggle with rapid trace-level detection of fibrosis. To address these limitations, a dual-channel nonlinear optical imaging system with excitation wavelengths at 780 nm and 820 nm was developed, enabling simultaneous spontaneous fluorescence and second-harmonic generation imaging through grid localization. This study applies dual-modality nonlinear imaging to achieve label-free, high-resolution visualization of pulmonary and renal fibrosis at the ECM microstructure scale. Through leveraging this system, it is demonstrated that collagen can be rapidly detected via spontaneous fluorescence at 780 nm, whereas the spatial distribution of collagen fibrils is precisely mapped using Second Harmonic Generation at 820 nm. This approach allows for the rapid and sensitive detection of trace fibrosis in a 5-day unilateral ureteral obstruction mouse model. Additionally, we identify that the elastic fibers, which can also be visualized, provide a foundation for staging diagnosis and delivering accurate and quantitative data for pathological studies and analysis. The research findings underscore the potential of this dual-channel nonlinear optical imaging system as a powerful tool for rapid, precise, and noninvasive fibrosis detection and staging. Full article
(This article belongs to the Section Optical and Photonic Biosensors)
Show Figures

Figure 1

13 pages, 2985 KiB  
Article
Characterization of the Second Harmonic Generation of Boron Nitride Nanotube Macroscopic Assemblies
by Ping Lu, Jingwen Guan, Cyril Hnatovsky, Huimin Ding, Kasthuri De Silva, Liliana Gaburici, Christopher Kingston and Stephen J. Mihailov
Nanomaterials 2025, 15(11), 861; https://doi.org/10.3390/nano15110861 - 3 Jun 2025
Viewed by 666
Abstract
Boron nitride nanotubes (BNNTs) are predicted to be promising one-dimensional nonlinear optical materials, but to date, only one experimental observation has been made using individual nanotubes. In this work, second harmonic generation (SHG) was achieved from free-standing bulk BNNT sheets and BNNT coatings [...] Read more.
Boron nitride nanotubes (BNNTs) are predicted to be promising one-dimensional nonlinear optical materials, but to date, only one experimental observation has been made using individual nanotubes. In this work, second harmonic generation (SHG) was achieved from free-standing bulk BNNT sheets and BNNT coatings on silica substrates. Focusing femtosecond infrared (fs-IR) laser pulses with a wavelength of 800 nm onto the BNNT assemblies resulted in strong SHG at a wavelength of 400 nm. It was observed that due to the thickness variation of the BNNT assemblies and orientational alignment of BNNTs in the assemblies, the intensity of the second-harmonic (SH) radiation changed dramatically when different locations on the samples were investigated. Among all the BNNT assemblies tested, the localized SH response and its dependence on the polarization of the excitation fs-IR pulses were the strongest in BNNT coatings produced by a dip-coating process. By measuring the SH response, the uniformity, reproducibility, and efficiency of BNNT deposition processes could be assessed. For applications requiring a high SH response from BNNT assemblies, the process of dip coating is preferred. Full article
(This article belongs to the Special Issue Linear and Nonlinear Optical Properties of Nanomaterials)
Show Figures

Figure 1

10 pages, 1167 KiB  
Article
Investigation of UV Picosecond Laser Damage Threshold of Anti-Reflection Coated Windows
by Priyadarshani Narayanasamy, Martin Mydlář, Hana Turčičová, Mihai George Mureșan, Ondřej Novák, Jan Vanda and Jan Brajer
J. Manuf. Mater. Process. 2025, 9(6), 180; https://doi.org/10.3390/jmmp9060180 - 29 May 2025
Viewed by 688
Abstract
Long-term stability and laser-induced damage resistance of optical components in the UV region are critical for enhancing their performance in UV high-power laser applications. This study evaluates the laser-induced damage threshold (LIDT) of commercially available UV optical windows with anti-reflective (AR) coating, produced [...] Read more.
Long-term stability and laser-induced damage resistance of optical components in the UV region are critical for enhancing their performance in UV high-power laser applications. This study evaluates the laser-induced damage threshold (LIDT) of commercially available UV optical windows with anti-reflective (AR) coating, produced through various coating techniques and designed for high-power lasers. A third-harmonic (343 nm) wavelength with good beam quality was generated in the picosecond regime to investigate the LIDT of optical components. The LIDT for each sample was measured under controlled conditions and compared based on their coating techniques. The sample coated with Al2O3/SiO2 through ion beam sputtering has the best LIDT value, of 0.6 J/cm2, among the tested samples, based on the hundred-thousand-pulses methodology. The damage threshold curve and the corresponding damage morphology are discussed in detail, and these findings provide insights into the durability and susceptibility of UV optics for advanced laser systems available in the market. Full article
Show Figures

Figure 1

8 pages, 1287 KiB  
Communication
0.74 W Broadband Degenerate Femtosecond MgO-Doped Periodically Poled Lithium Niobate (MgO: PPLN) Optical Parametric Oscillator at 2056 nm
by Yuxiang Zhao, Bobo Wang, Jinfang Yang, Taotao He, Hao Xu, Xue Qiu, Zhong Dong and Weijun Ling
Photonics 2025, 12(6), 543; https://doi.org/10.3390/photonics12060543 - 27 May 2025
Viewed by 364
Abstract
The degenerate optical parametric oscillator (OPO) is demonstrated to generate high-power, broadband mid-infrared MgO-doped periodically poled lithium niobate (MgO:PPLN) femtosecond laser at 151 MHz, synchronously pumped by a commercial Kerr-lens mode-locked Yb:KGW oscillator at 1028 nm. The average power of the degenerate OPO [...] Read more.
The degenerate optical parametric oscillator (OPO) is demonstrated to generate high-power, broadband mid-infrared MgO-doped periodically poled lithium niobate (MgO:PPLN) femtosecond laser at 151 MHz, synchronously pumped by a commercial Kerr-lens mode-locked Yb:KGW oscillator at 1028 nm. The average power of the degenerate OPO centered at 2056 nm is as high as 740 mW, which is the highest output power from a reported 2 μm degenerate femtosecond OPO, pumped by a bulk solid-state laser. The full width at half maximum (FWHM) spectral bandwidth of the degenerate OPO is 87.4 nm, corresponding to a theoretical, Fourier-limited pulse duration of 51 fs. These remarkable results indicate that degenerate OPO is a great potential candidate technology for generating high-power and few-cycle femtosecond pulses around 2 μm. Such mid-infrared sources are well-suited for high harmonic generation, a pumping source for mid- to far-infrared OPO. Full article
(This article belongs to the Special Issue Advances in Ultrafast Laser Science and Applications)
Show Figures

Figure 1

32 pages, 612 KiB  
Article
Improved Splitting-Integrating Methods for Image Geometric Transformations: Error Analysis and Applications
by Hung-Tsai Huang, Zi-Cai Li, Yimin Wei and Ching Yee Suen
Mathematics 2025, 13(11), 1773; https://doi.org/10.3390/math13111773 - 26 May 2025
Viewed by 424
Abstract
Geometric image transformations are fundamental to image processing, computer vision and graphics, with critical applications to pattern recognition and facial identification. The splitting-integrating method (SIM) is well suited to the inverse transformation T1 of digital images and patterns, but it encounters [...] Read more.
Geometric image transformations are fundamental to image processing, computer vision and graphics, with critical applications to pattern recognition and facial identification. The splitting-integrating method (SIM) is well suited to the inverse transformation T1 of digital images and patterns, but it encounters difficulties in nonlinear solutions for the forward transformation T. We propose improved techniques that entirely bypass nonlinear solutions for T, simplify numerical algorithms and reduce computational costs. Another significant advantage is the greater flexibility for general and complicated transformations T. In this paper, we apply the improved techniques to the harmonic, Poisson and blending models, which transform the original shapes of images and patterns into arbitrary target shapes. These models are, essentially, the Dirichlet boundary value problems of elliptic equations. In this paper, we choose the simple finite difference method (FDM) to seek their approximate transformations. We focus significantly on analyzing errors of image greyness. Under the improved techniques, we derive the greyness errors of images under T. We obtain the optimal convergence rates O(H2)+O(H/N2) for the piecewise bilinear interpolations (μ=1) and smooth images, where H(1) denotes the mesh resolution of an optical scanner, and N is the division number of a pixel split into N2 sub-pixels. Beyond smooth images, we address practical challenges posed by discontinuous images. We also derive the error bounds O(Hβ)+O(Hβ/N2), β(0,1) as μ=1. For piecewise continuous images with interior and exterior greyness jumps, we have O(H)+O(H/N2). Compared with the error analysis in our previous study, where the image greyness is often assumed to be smooth enough, this error analysis is significant for geometric image transformations. Hence, the improved algorithms supported by rigorous error analysis of image greyness may enhance their wide applications in pattern recognition, facial identification and artificial intelligence (AI). Full article
Show Figures

Figure 1

12 pages, 1339 KiB  
Article
Two-Photon Microscopy for the Investigation of Morphological and Quantitative Changes in Skin Chrono- and Photo-Aging
by Stefano Bighetti, Chiara Rovati, Luca Bettolini, Mariachiara Arisi, Mariateresa Rossi, Cosetta Ravelli, Sara Rovaris, Marina Venturini, Stefania Mitola and Piergiacomo Calzavara-Pinton
Cosmetics 2025, 12(3), 111; https://doi.org/10.3390/cosmetics12030111 - 26 May 2025
Viewed by 702
Abstract
Introduction: Skin aging is influenced both by intrinsic factors and environmental exposures, such as UV radiation, which accelerate structural changes within the skin’s extracellular matrix (ECM). Understanding these changes is crucial for developing effective anti-aging treatments. Materials and Methods: This pilot cross-sectional study [...] Read more.
Introduction: Skin aging is influenced both by intrinsic factors and environmental exposures, such as UV radiation, which accelerate structural changes within the skin’s extracellular matrix (ECM). Understanding these changes is crucial for developing effective anti-aging treatments. Materials and Methods: This pilot cross-sectional study examined skin biopsy samples from three Caucasian male subjects with different levels of UV exposure, aiming to evaluate the effectiveness of two-photon microscopy (2PM) and Second Harmonic Generation (SHG) in visualizing and quantifying structural changes associated with skin aging. The samples were analyzed using 2PM to assess the structure and density of collagen and elastin fibers within the ECM. Integrated optical density (IOD) and the SHG-to-Autofluorescence Aging Index of the Dermis (SAAID) were used for quantitative analysis. Results: This study revealed a significant decrease in collagen density and increased disorganization in the ECM with age. Photo-exposed skin showed a more pronounced degradation of collagen and a higher increase in elastin content compared to non-photo-exposed skin. The average IOD for collagen was notably lower in elderly subjects compared to younger subjects, with a marked decrease in chronically photo-exposed skin. Discussion: The SAAID values indicated a substantial impact of photoaging, with lower scores in photo-exposed elderly skin compared to non-exposed skin. Conclusions: In conclusion, 2PM and SHG microscopy were effective in visualizing and quantifying age- and UV-induced skin remodeling, providing valuable insights into the distinct mechanisms driving intrinsic and extrinsic aging. Full article
(This article belongs to the Special Issue Feature Papers in Cosmetics in 2025)
Show Figures

Figure 1

10 pages, 1391 KiB  
Article
Precise Temperature Measurement Through Wavelength Modulation Heterodyne Phase-Sensitive Dispersion Spectroscopy
by Guoquan Wang, Rende Wang and Weiqian Zhao
Photonics 2025, 12(6), 537; https://doi.org/10.3390/photonics12060537 - 26 May 2025
Viewed by 412
Abstract
This work proposes a precise temperature measurement method based on wavelength modulation heterodyne phase-sensitive dispersion spectroscopy (WM-HPSDS). Before the light intensity of the laser was modulated by an electro-optic modulator to generate a three-tone beam, the laser produced additional wavelength modulation by superimposing [...] Read more.
This work proposes a precise temperature measurement method based on wavelength modulation heterodyne phase-sensitive dispersion spectroscopy (WM-HPSDS). Before the light intensity of the laser was modulated by an electro-optic modulator to generate a three-tone beam, the laser produced additional wavelength modulation by superimposing a high-frequency sinusoidal waveform on a slow sawtooth wave. The second harmonic peak value of the H2O dispersion phase at 7185.59 cm−1 and 7182.94 cm−1 was used to extract temperature through two-line thermometry. The experiment was carried out on a water-based thermostat and an acoustically excited Bunsen burner. The extracted temperatures of the thermostat agreed well with the reference temperature, and the deviation was within 1.5 °C. The measurement stability of the Bunsen burner flame was approximately 10.4 dB higher than that of direct HPSDS. Furthermore, measuring the peak values under varying laser powers demonstrated that WM-HPSDS was immune to optical power fluctuations. Therefore, this method has potential for measuring temperature in harsh environments. Full article
(This article belongs to the Section Lasers, Light Sources and Sensors)
Show Figures

Figure 1

8 pages, 1558 KiB  
Communication
High-Capacity Near-Infrared Optical Vortex Sorting and Detection by Nonlinear Dammann Vortex Grating
by Hui Zhao, Ruwei Zhao, Qilu Liu, Yan Sheng and Tianxiang Xu
Photonics 2025, 12(6), 532; https://doi.org/10.3390/photonics12060532 - 23 May 2025
Viewed by 338
Abstract
This paper demonstrates the sorting and detection of near-infrared vortex light using a nonlinear Dammann vortex grating. By incorporating a forked structure into the nonlinear Dammann grating, the resulting nonlinear Dammann vortex grating is capable of converting near-infrared Gaussian light into a visible [...] Read more.
This paper demonstrates the sorting and detection of near-infrared vortex light using a nonlinear Dammann vortex grating. By incorporating a forked structure into the nonlinear Dammann grating, the resulting nonlinear Dammann vortex grating is capable of converting near-infrared Gaussian light into a visible vortex array. The array comprises 49 independent detection channels, each of which can precisely control the inherent topological charge values. When the topological charge value of a detection channel’s vortex light matches that of the incident vortex, the vortex degenerates into a Gaussian spot, thereby enabling the detection of the incident vortex’s topological charge. Our experimental results show that this grating, with its 49 independent detection channels, can detect the topological charge values of vortex light in the near-infrared range from l = −12 to +12 in real-time. Compared to existing solutions, this grating offers enhanced versatility and has potential applications in optical communication systems for the transmission, reception, and multiplexing of OV beams. Full article
Show Figures

Figure 1

Back to TopTop