You seem to have javascript disabled. Please note that many of the page functionalities won't work as expected without javascript enabled.

Search for Articles:

Title / Keyword

Author / Affiliation / Email

Journal

Article Type

Advanced Search

Section

Special Issue

Volume

Issue

Number

Page

Logical OperatorOperator

Search Text

Search Type

Phase Retrieval of One-Dimensional Objects by the Multiple-Plane Gerchberg–Saxton Algorithm Implemented into a Digital Signal Processor
Investigating Quantum Confinement and Enhanced Luminescence in Nanoporous Silicon: A Photoelectrochemical Etching Approach Using Multispectral Laser Irradiation

Journal Description

Optics

Optics is an international, peer-reviewed, open access journal on optics published quarterly online by MDPI.

Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
High Visibility: indexed within ESCI (Web of Science), Scopus, EBSCO, and other databases.
Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 18.4 days after submission; acceptance to publication is undertaken in 3.9 days (median values for papers published in this journal in the second half of 2024).
Recognition of Reviewers: APC discount vouchers, optional signed peer review, and reviewer names published annually in the journal.

Impact Factor: 1.1 (2023); 5-Year Impact Factor: 1.1 (2023)

Imprint Information Journal Flyer Open Access ISSN: 2673-3269

Latest Articles

16 pages, 4654 KiB

Open AccessArticle

Measurement Method of Refractive Index for Optical Lenses Based on Curvature Radius Fitting of Small-Sized Aspheric Surfaces

by Tao Zhong, Guangyan Guo, Yasong Chow, Yixuan Yang, Tianhao Zhang, Jiru Yang, Mingxuan Lu, Yonghuan Wang, Yongjian Zhu, Tianlei Jia, Yishi Shi and Changjun Ke

Optics 2025, 6(1), 4; https://doi.org/10.3390/opt6010004 - 20 Jan 2025

The study of the refractive index of traditional lenses is one of the foundational topics in the field of optics. The refractive index of a lens determines its ability to refract and focus light, making it a key parameter in optical design and [...] Read more.

The study of the refractive index of traditional lenses is one of the foundational topics in the field of optics. The refractive index of a lens determines its ability to refract and focus light, making it a key parameter in optical design and applications. For the measurement of the refractive index of blind samples of finished lenses, this paper proposes a measurement method based on the use of a focal length measuring instrument and an aspheric profilometer to measure the surface shape data of the front and back surfaces of the lens. This method combines curve fitting algorithms and curvature radius fitting algorithms, ultimately reconstructing the lens model using Zemax and back-calculating the refractive index of the lens. For the samples employed in this paper, the measurement accuracy of the focal length can achieve 1.06%, the fitting accuracy of the curvature radius can reach 0.138%, and the recovery accuracy of the refractive index can attain 6.303 × 10⁻⁴%. Full article

► Show Figures

Figure 1

10 pages, 3419 KiB

Open AccessArticle

An All-Fiber Curvature Sensor with High Sensitivity Based on Sphere-Shaped Misaligned Structure

by Xiaowei Li, Qiangshen Chen, Mengyu Ren and Guoying Feng

Optics 2025, 6(1), 3; https://doi.org/10.3390/opt6010003 - 17 Jan 2025

In this paper, a high-linear-sensitivity fiber curvature sensor based on the sphere-shaped misaligned structure (SSMS) with few-mode fiber (FMF) and single-mode fiber (SMF) was proposed and demonstrated. A spherical structure was prepared at one end of a few-mode fiber, which could effectively excite [...] Read more.

In this paper, a high-linear-sensitivity fiber curvature sensor based on the sphere-shaped misaligned structure (SSMS) with few-mode fiber (FMF) and single-mode fiber (SMF) was proposed and demonstrated. A spherical structure was prepared at one end of a few-mode fiber, which could effectively excite higher-order modes and generate interference in the misaligned cascade. When external environmental parameters changed, the resonance peaks formed by intermodal interference were displaced, and the shifts generated by different resonant peaks were also different. The experimental results show that the maximum curvature sensitivity was −2.220 nm/m⁻¹, and the linear fitting coefficient reached up to 0.991, which is an extremely high sensitivity among wavelength-modulated curvature sensors. Meanwhile, the strain sensitivity of the sensor was as low as 7.99 pm/μ

\bar{ε}

, and the temperature sensitivity was 3.958 pm/°C, which is a low temperature sensitivity and low strain sensitivity, and solves the cross-sensitivity problem. With advantages of simple manufacture, low cost, and favorable stability, the sensor is expected to be one of the best candidate instruments for measuring curvature and inclination. Full article

(This article belongs to the Special Issue Optical Sensing and Optical Physics Research)

► Show Figures

Figure 1

11 pages, 1863 KiB

Open AccessArticle

Highly Precise Time Compensation Algorithm for Synchronous Communication System Based on Least Squares

by Jin Su, Changshui Li, Qingbo Liu, Sheng Zhao and Xiangyu Wang

Optics 2025, 6(1), 2; https://doi.org/10.3390/opt6010002 - 9 Jan 2025

Time synchronization is an important technology in synchronous communication systems to ensure the accuracy of data transmission. Precise time synchronization allows the receiver to correctly interpret the signal at the correct moment. However, as communication rates increase and application scenarios diversify, pulse signal [...] Read more.

Time synchronization is an important technology in synchronous communication systems to ensure the accuracy of data transmission. Precise time synchronization allows the receiver to correctly interpret the signal at the correct moment. However, as communication rates increase and application scenarios diversify, pulse signal reception quality is often affected by factors such as noise interference and clock stability. In order to address these challenges, we propose a pulse signal recovery method utilizing the least squares algorithm to complete time compensation. By fitting and optimizing the received signal, we can obtain estimated values that closely approximate the actual time, thereby achieving enhanced precision in time synchronization. The results demonstrate that this method effectively reduces estimation errors, improving the system’s time synchronization accuracy to the

n s

level. This method not only provides an effective solution for enhancing time synchronization precision but also lays the foundation for time synchronization performance in the future. Full article

► Show Figures

Figure 1

11 pages, 2799 KiB

Open AccessArticle

Shortwave near Infrared–Hyperspectral Imaging Spectra to Detect Pork Adulteration in Beef Using Partial Least Square Regression Coupled with VIP Wavelength Selections Method

by Rudiati Evi Masithoh, Reza Adhitama Putra Hernanda, Muhammad Fahri Reza Pahlawan, Juntae Kim, Hanim Zuhrotul Amanah and Byoung-Kwan Cho

Optics 2025, 6(1), 1; https://doi.org/10.3390/opt6010001 - 3 Jan 2025

Pork adulteration detection in beef is important due to health, economic, and religious concerns. This study explored the use of a Shortwave Near Infrared–Hyperspectral Imaging (SWNIR–HSI) system which captured spectral data across 894–2504 nm to detect adulteration of pork in beef. In this [...] Read more.

Pork adulteration detection in beef is important due to health, economic, and religious concerns. This study explored the use of a Shortwave Near Infrared–Hyperspectral Imaging (SWNIR–HSI) system which captured spectral data across 894–2504 nm to detect adulteration of pork in beef. In this study, minced pork in various concentrations ranging from 0–50% (w/w) were added to pure minced beef. Spectra obtained from the SWNIR–HSI were used to develop a partial least square regression (PLSR) model. The study compared the PLSR results between full wavelengths (variables) and selected wavelengths obtained via the variable importance in projection (VIP) method. The best results from the full-wavelength PLSR model yielded a prediction accuracy (R²P) of 0.940 and a standard error of prediction (SEP) of 4.633%, while using VIP-selected wavelengths improved performance, with R²P of 0.955 and SEP of 3.811%. The study demonstrates the potency of SWNIR–HIS, particularly with selected wavelengths, as an effective and nondestructive tool for accurately predicting pork adulteration levels in beef. Full article

► Show Figures

Figure 1

11 pages, 2901 KiB

Open AccessArticle

Geometrical and Optical Properties of Optical Components Manufactured by Means of Stereolithography

by Dominic Bartels, Miriam Heise and Michael Schmidt

Optics 2024, 5(4), 611-621; https://doi.org/10.3390/opt5040045 - 9 Dec 2024

Additive manufacturing (AM) is a fast-growing technology that supports the rapid fabrication of prototypes. Already, employing AM technologies in early product development stages can help to accelerate the time from conceptualisation phase to the market entry. Furthermore, advances in the field of materials, [...] Read more.

Additive manufacturing (AM) is a fast-growing technology that supports the rapid fabrication of prototypes. Already, employing AM technologies in early product development stages can help to accelerate the time from conceptualisation phase to the market entry. Furthermore, advances in the field of materials, such as highly transparent resins in the visible wavelength spectrum, also open application potentials for the design and fabrication of optical components. Three highly transparent resins from different suppliers are studied in this work regarding their influence on the geometrical and optical properties of additively manufactured components. The different materials were processed using a masked stereolithography 3D printer. Geometrical and optical properties of the generated test samples were analysed by means of laser scanning microscopy and spectrophotometry, respectively. A clear correlation between optical properties of the resin and the solidified samples was identified. It was further found that while spin coating does not significantly affect the geometrical properties, a strong influence on the resulting optical properties could be observed. The highest transmission properties, in the range of up to 90%, were determined for samples that were spin-coated on both surfaces. Thus, applying a spin coating operation to additively manufactured optical components is recommended for the highest transmission properties. Full article

► Show Figures

Figure 1

16 pages, 15984 KiB

Open AccessArticle

Development of a Portable Optomechatronic System to Obtain the Characterization of Transparent Materials and Dielectric Thin Films

by Araceli Sánchez-Alvarez, Osvaldo Rodríguez-Quiroz, Gabriela Elizabeth Quintanilla-Villanueva, Melissa Marlene Rodríguez-Delgado, Juan Francisco Villarreal-Chiu, Oscar Javier Silva-Hernández and Donato Luna-Moreno

Optics 2024, 5(4), 595-610; https://doi.org/10.3390/opt5040044 - 5 Dec 2024

This paper outlines the design and fabrication of a portable optomechatronic system based on the theta-2theta configuration, which explores various optical characterization techniques for transparent materials and dielectric thin films. These techniques include Brewster angle and Abelès-Brewster angle measurements, critical angle measurements, and [...] Read more.

This paper outlines the design and fabrication of a portable optomechatronic system based on the theta-2theta configuration, which explores various optical characterization techniques for transparent materials and dielectric thin films. These techniques include Brewster angle and Abelès-Brewster angle measurements, critical angle measurements, and the surface plasmon resonance technique. The system consists of a mechanical assembly of rotating stages, a semiconductor laser, a photodiode connected to a data acquisition card, and a user interface for controlling the stepper motor rotation stages. Utilizing a BK7 substrate, the motorized stage achieved a resolution of 0.010. The Brewster angle measured was 56.550, with a refractive index (n) of 1.5137. The relative error obtained was Δn/n = 3.82 × 10⁻⁴, with a sensitivity of 164.27 RIU/degree and an accuracy of 0.37/degree. Furthermore, the discrepancies between theoretical and experimental refractive indices for different prisms at 639 nm ranged from ±7 × 10⁻⁴ to ±73 × 10⁻⁴. After testing various samples, the system demonstrated its capability to perform fast, precise, and non-invasive measurements. Its portability allows for use in diverse environments and applications. Full article

► Show Figures

Figure 1

14 pages, 4925 KiB

Open AccessArticle

Dynamic Control of Airy Beams Using Real-Time Phase-Amplitude Encoding on a Spatial Light Modulator

by Alpgiray Keskin, Gamze Kaya, Necati Kaya, James Strohaber, Alexandre A. Kolomenskii and Hans A. Schuessler

Optics 2024, 5(4), 581-594; https://doi.org/10.3390/opt5040043 - 3 Dec 2024

Airy beams showing curved paths have found extensive applications in fields such as optical trapping, biomedical analysis, and material processing. Despite their utility, dynamic control of Airy beams poses a significant challenge. This work investigates the experimental realization of dynamic steering of Airy [...] Read more.

Airy beams showing curved paths have found extensive applications in fields such as optical trapping, biomedical analysis, and material processing. Despite their utility, dynamic control of Airy beams poses a significant challenge. This work investigates the experimental realization of dynamic steering of Airy beams by utilizing computer-generated holograms with phase-amplitude encoding on a phase-only spatial light modulator (SLM). We successfully generated and controlled Airy beams by imposing dynamic phase masks that manipulated both the phase and amplitude of the field, which sets our approach apart from conventional methods with only phase manipulation. By directly encoding in situ such a hologram and transferring it to an SLM, we are able to control the initial position and rotational orientation of Airy beams without relying on mechanical movement or traditional optical setups involving lenses and apertures. Generating Airy beams in any initial position and rotational direction is anticipated to significantly impact applications such as optical trapping, optical communication, and biomedical imaging by providing a flexible platform for dynamic Airy beam manipulation. Full article

(This article belongs to the Topic The Extended Technological Platform Based on Optics and Microwaves: Conventional and Hybrid Solutions)

► Show Figures

Figure 1

15 pages, 4229 KiB

Open AccessArticle

Self-Adaptive Moving Least Squares Measurement Based on Digital Image Correlation

by Hengsi Zhu, Yurong Guo and Xiao Tan

Optics 2024, 5(4), 566-580; https://doi.org/10.3390/opt5040042 - 2 Dec 2024

Digital image correlation (DIC) is a non-contact measurement technique used to evaluate surface deformation of objects. Typically, pointwise moving least squares (PMLS) fitting is applied to process the noisy data from DIC to obtain an accurate strain field. In this study, a self-adaptive [...] Read more.

Digital image correlation (DIC) is a non-contact measurement technique used to evaluate surface deformation of objects. Typically, pointwise moving least squares (PMLS) fitting is applied to process the noisy data from DIC to obtain an accurate strain field. In this study, a self-adaptive pointwise moving least squares (SPMLS) method was developed to optimize the process of window size selection, thereby attaining superior accuracy in measurements. The premise of this method is that the noise in the displacement field follows white Gaussian noise. Under this assumption, it analyses the random errors and systematic errors of the PMLS method under different calculation window sizes. The optimal size of the calculation window is determined by minimizing the errors. Subsequently, the strain field is computed based on the optimized calculation window. The results were compared with a typical PMLS method. Whether calculating low-gradient strain fields or high-gradient strain fields, the computational accuracy of SPMLS is close to the optimal accuracy of PMLS. This study effectively addresses the inherent challenge of manually selecting window size in the PMLS method. Full article

► Show Figures

Figure 1

22 pages, 73175 KiB

Open AccessArticle

Multiplane Optimizing Phase Holograms Using Advanced Machine Learning Algorithms and GPU Acceleration

by Luz Hernández-Felipe, José Humberto Arroyo-Nuñez, César Camacho-Bello and Iván Rivas-Cambero

Optics 2024, 5(4), 544-565; https://doi.org/10.3390/opt5040041 - 25 Nov 2024

Phase holography is a critical optical imaging and information processing technique with applications ranging from microscopy to optical communications. However, optimizing phase hologram generation remains a significant challenge due to the non-convex nature of the optimization problem. This paper presents a novel multiplane [...] Read more.

Phase holography is a critical optical imaging and information processing technique with applications ranging from microscopy to optical communications. However, optimizing phase hologram generation remains a significant challenge due to the non-convex nature of the optimization problem. This paper presents a novel multiplane optimization approach for phase hologram generation to minimize the reconstruction error across multiple focal planes. We significantly improve holographic reconstruction quality by integrating advanced machine learning algorithms like RMSprop and Adam with GPU acceleration. The proposed method utilizes TensorFlow to implement custom propagation layers, optimizing the phase hologram to reduce errors at strategically selected distances. Full article

► Show Figures

Figure 1

10 pages, 1979 KiB

Open AccessArticle

Determining the Magic Wavelength Without Modulation of the Trap Depth

by Jingjing Xia, Feng Guo, Yanhua Zhou, Xiaotong Lu and Hong Chang

Optics 2024, 5(4), 534-543; https://doi.org/10.3390/opt5040040 - 22 Nov 2024

In this paper, the magic wavelength of the ⁸⁷Sr optical lattice clock is determined by a method that bypasses the need for lattice trap depth modulation. Instead, it relies on an additional AC Stark shift generated by a dipole beam operating near [...] Read more.

In this paper, the magic wavelength of the ⁸⁷Sr optical lattice clock is determined by a method that bypasses the need for lattice trap depth modulation. Instead, it relies on an additional AC Stark shift generated by a dipole beam operating near the frequency of the lattice light and oriented perpendicular to the optical lattice. The magic wavelength is inferred by measuring the AC Stark shift induced by the dipole beam as a function of its power under various frequency detunings. The effect of the dipole beam on the external states of the cold ensemble is evaluated through comparative analysis of the radial and axial sideband spectra, both with and without the dipole beam. Variations in density shift resulting from changes in external states are evaluated using comprehensive numerical calculations. By avoiding trap depth modulation, this method effectively suppresses the influence of the density shift, thereby offering a promising avenue for accurately determining the magic wavelength. Full article

(This article belongs to the Section Photonics and Optical Communications)

► Show Figures

Figure 1

11 pages, 7949 KiB

Open AccessArticle

Dynamic Excitation of Surface Plasmon Polaritons with Vector Laguerre–Gaussian Beams

by Aldo Peña-Ramírez, Tingting Zhai, Rafael Salas-Montiel and Víctor Ruiz-Cortés

Optics 2024, 5(4), 523-533; https://doi.org/10.3390/opt5040039 - 21 Nov 2024

We investigate the dynamic excitation of surface plasmon polaritons (SPPs) using vector Laguerre–Gauss (LG) beams, which offer unique properties for manipulating the polarization and spatial distribution of light. Our study demonstrates the efficient coupling of SPPs with LG beams, characterized by their azimuthal [...] Read more.

We investigate the dynamic excitation of surface plasmon polaritons (SPPs) using vector Laguerre–Gauss (LG) beams, which offer unique properties for manipulating the polarization and spatial distribution of light. Our study demonstrates the efficient coupling of SPPs with LG beams, characterized by their azimuthal and radial indices

(m, p)

, as well as polarization distribution type. Numerical simulations reveal that the vector nature of LG beams enables selective excitation of SPPs, depending on the polarization type of the beam. Experimental verification of our simulations is achieved using a gold circular Bragg grating and a spatial light modulator that generates vector LG beams. Leakage radiation imaging demonstrates the potential of vector LG beams for dynamic SPP excitation and manipulation. This study opens novel ways for the control of SPPs in plasmonic devices, such as modulators, and nanophotonic circuits. Full article

► Show Figures

Figure 1

9 pages, 2156 KiB

Open AccessArticle

Phase Retrieval of One-Dimensional Objects by the Multiple-Plane Gerchberg–Saxton Algorithm Implemented into a Digital Signal Processor

by Varis Karitans, Maris Ozolinsh and Sergejs Fomins

Optics 2024, 5(4), 514-522; https://doi.org/10.3390/opt5040038 - 20 Nov 2024

In the current study, we address the phase retrieval of one-dimensional phase objects from near-field diffraction patterns using the multiple-plane Gerchberg–Saxton algorithm, which is still widely used for phase retrieval. The algorithm was implemented in a low-cost digital signal processor capable of fast [...] Read more.

In the current study, we address the phase retrieval of one-dimensional phase objects from near-field diffraction patterns using the multiple-plane Gerchberg–Saxton algorithm, which is still widely used for phase retrieval. The algorithm was implemented in a low-cost digital signal processor capable of fast Fourier transform using Q15 arithmetic, which is used by the previously mentioned algorithm. We demonstrate similarity between one-dimensional phase objects, i.e., vectors cut out of a phase map of the tertiary spherical aberration retrieved by the multiple-plane Gerchberg–Saxton algorithm, and these vectors are measured with a non-contact profiler. The tertiary spherical aberration was induced by a phase plate fabricated using grayscale lithography. After subtracting the vectors retrieved by the algorithm from those measured with the profiler, the root mean square error decreased, while a corresponding increase in the Strehl ratio was observed. A single vector of size 64 pixels was retrieved in about 2 min. The results suggest that digital signal processors that are capable of one-dimensional FFT and fixed-point arithmetic in Q15 format can successfully retrieve the phase of one-dimensional objects, and they can be used for applications that do not require real-time operation, i.e., analyzing the quality of cylindrical micro-optics. Full article

(This article belongs to the Section Engineering Optics)

► Show Figures

Figure 1

28 pages, 36183 KiB

Open AccessFeature PaperArticle

Optimization of Laser-Patterned Superhydrophilic–Superhydrophobic Surfaces on 304 Stainless Steel for Enhanced Fog Water Collection

by Hongda Chen, Jingnan Zhao, Wenjian Ma, Zhiquan Guo and Yuanchen Cui

Optics 2024, 5(4), 486-513; https://doi.org/10.3390/opt5040037 - 19 Nov 2024

This study focuses on creating micro-nano structures on the surface of 304 stainless steel using nanosecond lasers to achieve superhydrophobicity for fog water collection experiments in a fog chamber. By adjusting pattern parameters, an uneven wettability surface was processed, and six samples were [...] Read more.

This study focuses on creating micro-nano structures on the surface of 304 stainless steel using nanosecond lasers to achieve superhydrophobicity for fog water collection experiments in a fog chamber. By adjusting pattern parameters, an uneven wettability surface was processed, and six samples were placed at different positions in the chamber to study water collection efficiency from various surfaces. The experimental results indicate that the water collection efficiency of the patterned superhydrophobic surface is superior to that of the original surface, with the front sample collecting 0.4524 ± 0.005 g of water, representing a 90.38% improvement. As the kinetic energy of the fog flow gradually diminishes, a total of 1.1913 ± 0.005 g of water was collected, achieving a 60.25% improvement. The study also investigates the durability and optimal temperature conditions for fog water collection, ultimately achieving 1.4781 ± 0.005 g of water collection in a 5 °C fog environment, resulting in a 98.83% enhancement. Full article

► Show Figures

Figure 1

9 pages, 2631 KiB

Open AccessArticle

Repeat Versus Primary Photorefractive Keratectomy for Treatment of Myopia

by Michael Mimouni, Arie Y. Nemet, Dror Ben Ephraim Noyman, Gilad Rabina, Avia Yossefi and Igor Kaiserman

Optics 2024, 5(4), 477-485; https://doi.org/10.3390/opt5040036 - 19 Nov 2024

Although effective, a portion of photorefractive keratectomy (PRK) patients will suffer residual myopia or relapse to myopic regression. This retrospective, non-randomized, comparative study, aimed to compare the efficacy of primary PRK versus PRK performed as retreatment after previous surgery for myopia. Data regarding [...] Read more.

Although effective, a portion of photorefractive keratectomy (PRK) patients will suffer residual myopia or relapse to myopic regression. This retrospective, non-randomized, comparative study, aimed to compare the efficacy of primary PRK versus PRK performed as retreatment after previous surgery for myopia. Data regarding the right eye of 220 consecutive myopic patients undergoing repeat or primary PRK in 2013–2017 were extracted. Groups were matched for demographics and preoperative spherical equivalent, sphere, astigmatism, uncorrected and corrected distance visual acuity (UDVA and CDVA). Primary outcomes were an efficacy index (ratio between the postoperative UDVA and the preoperative CDVA), a safety index (ratio between the postoperative and the preoperative CDVA), postoperative UDVA and CDVA, and deviation from target refraction. Primary PRK showed significant superiority in logMAR UDVA (0.01 ± 0.05 versus 0.05 ± 0.10, p = 0.001), logMAR CDVA (0.01 ± 0.05 versus 0.04 ± 0.08, p = 0.01), efficacy index (1.00 ± 0.05 versus 0.97 ± 0.09, p = 0.003) and safety index (1.00 ± 0.06 versus 0.98 ± 0.08, p = 0.04) compared to repeat PRK, but had a significantly higher share of patients with postoperative spherical equivalent (74.5% versus 67.3%) and cylinder (74.5% versus 68.2%) in the range of ±0.5 D. To conclude, enhancement PRK leads to inferior efficacy and safety with greater deviation from target refraction. Adjusted nomograms for repeat PRK may be warranted. Full article

► Show Figures

Figure 1

12 pages, 3271 KiB

Open AccessArticle

Investigating Quantum Confinement and Enhanced Luminescence in Nanoporous Silicon: A Photoelectrochemical Etching Approach Using Multispectral Laser Irradiation

by Chao-Ching Chiang and Philip Nathaniel Immanuel

Optics 2024, 5(4), 465-476; https://doi.org/10.3390/opt5040035 - 13 Nov 2024

This study explores electrochemical etching to form porous silicon (PS), which has diverse biomedical and energy applications. Our objective is to gain new insights and drive significant scientific and technological advancements. Specifically, we study the effect of electrochemical etching of P-type silicon using [...] Read more.

This study explores electrochemical etching to form porous silicon (PS), which has diverse biomedical and energy applications. Our objective is to gain new insights and drive significant scientific and technological advancements. Specifically, we study the effect of electrochemical etching of P-type silicon using laser irradiation in a hydrofluoric acid (HF) solution. The formation of the nanoscale PS structure can be successfully controlled by incorporating laser irradiation into the electrochemical etching process. The wavelength and power of the laser influence the formation of nanoporous silicon (NPS) on the surface during the electrochemical etching process. The luminous flux is monitored with the help of a customized integrating sphere system and an LED-based excitation source to find the light flux values distributed across the P-type nanolayer PS wafers. Analysis of the NPS and luminescence characteristics shows that the laser bandwidth controls the band gap energy absorption (BEA) phenomenon during the electrothermal reaction. It is demonstrated that formation of the NPS layer can be controlled in this combined laser irradiation and electrochemical etching technique by adjusting the range of the laser wavelength. This also allows for further precise control of the numerical trend of the luminous flux. Full article

► Show Figures

Figure 1

13 pages, 1168 KiB

Open AccessArticle

Exact Equations for the Back and Effective Focal Lengths of a Plano-Concave Thick Lens

by Víctor M. Durán-Ramírez, Jesús Muñoz-Maciel, Francisco J. Casillas-Rodríguez, Miguel Mora-Gonzalez and Francisco G. Peña-Lecona

Optics 2024, 5(4), 452-464; https://doi.org/10.3390/opt5040034 - 12 Nov 2024

In this work, we present the exact equations for the back and effective focal lengths of a plano-concave thick lens. These equations are derived through a detailed ray-tracing approach, calculating the meridional ray’s path parallel to the optical axis while taking into account [...] Read more.

In this work, we present the exact equations for the back and effective focal lengths of a plano-concave thick lens. These equations are derived through a detailed ray-tracing approach, calculating the meridional ray’s path parallel to the optical axis while taking into account lens thickness, refractive index, and surface curvature. Our analysis bridges the gap between paraxial approximations and exact ray behavior, highlighting how traditional models (e.g., thin-lens equations) can be extended to thick lenses. Additionally, we review recent advancements in negative refraction and surface phase manipulation techniques to demonstrate how our equations compare to modern numerical methods and metacoating-enhanced designs. This work provides a comprehensive and exact framework for understanding the optical properties of plano-concave thick lenses, offering new insights into their application in precision optics. Full article

(This article belongs to the Section Engineering Optics)

► Show Figures

Figure 1

7 pages, 2057 KiB

Open AccessArticle

Spectrum Broadening Due to Nonselective Linear Absorption

by Xingchu Zhang and Weilong She

Optics 2024, 5(4), 445-451; https://doi.org/10.3390/opt5040033 - 28 Oct 2024

The position and linewidth of an emission spectrum reflect the physical properties of the luminophor. So, keeping the spectrum from distortion is very important in its measurement. However, we find that the spectrum linewidth will be broadened when the near-infrared radiation from a [...] Read more.

The position and linewidth of an emission spectrum reflect the physical properties of the luminophor. So, keeping the spectrum from distortion is very important in its measurement. However, we find that the spectrum linewidth will be broadened when the near-infrared radiation from a sodium lamp passes through a nonselective linear absorbing filter. This counterintuitive linewidth-broadening phenomenon is obvious when the residual light power after the filter is low enough, typically lower than

2.48 \times 10^{- 4} μ W

. This novel linewidth-broadening effect is different from the well-known Lorentzian, Doppler, and Voigt broadening, and is likely to be more independent evidence of the discrete wavelet structure of classical plane light waves. The effect is significant in high-sensitivity spectroscopy measurements, for example streak camera spectroscopy and Raman spectroscopy experiments. In addition, this effect may also be significant for cosmological research. Full article

► Show Figures

Figure 1

11 pages, 1320 KiB

Open AccessArticle

Mobility Support with Intelligent Obstacle Detection for Enhanced Safety

by Jong Hyeok Han, Inkwon Yoon, Hyun Soo Kim, Ye Bin Jeong, Ji Hwan Maeng, Jinseok Park and Hee-Jae Jeon

Optics 2024, 5(4), 434-444; https://doi.org/10.3390/opt5040032 - 24 Oct 2024

In recent years, assistive technology usage among the visually impaired has risen significantly worldwide. While traditional aids like guide dogs and white canes have limitations, recent innovations like RFID-based indoor navigation systems and alternative sensory solutions show promise. Nevertheless, there is a need [...] Read more.

In recent years, assistive technology usage among the visually impaired has risen significantly worldwide. While traditional aids like guide dogs and white canes have limitations, recent innovations like RFID-based indoor navigation systems and alternative sensory solutions show promise. Nevertheless, there is a need for a user-friendly, comprehensive system to address spatial orientation challenges for the visually impaired. This research addresses the significance of developing a deep learning-based walking assistance device for visually impaired individuals to enhance their safety during mobility. The proposed system utilizes real-time ultrasonic sensors attached to a cane to detect obstacles, thus reducing collision risks. It further offers real-time recognition and analysis of diverse obstacles, providing immediate feedback to the user. A camera distinguishes obstacle types and conveys relevant information through voice assistance. The system’s efficacy was confirmed with a 90–98% object recognition rate in tests involving various obstacles. This research holds importance in providing safe mobility, promoting independence, leveraging modern technology, and fostering social inclusion for visually impaired individuals. Full article

(This article belongs to the Topic Color Image Processing: Models and Methods (CIP: MM))

► Show Figures

Figure 1

18 pages, 7213 KiB

Open AccessReview

A Review of Non-Linear Optical Imaging Techniques for Cancer Detection

by Francisco J. Ávila

Optics 2024, 5(4), 416-433; https://doi.org/10.3390/opt5040031 - 16 Oct 2024

Cited by 1

The World Health Organization (WHO) cancer agency predicts that more than 35 million cases of cancer will be experienced in 2050, a 77% increase over the 2022 estimate. Currently, the main cancers diagnosed are breast, lung, and colorectal. There is no standardized tool [...] Read more.

The World Health Organization (WHO) cancer agency predicts that more than 35 million cases of cancer will be experienced in 2050, a 77% increase over the 2022 estimate. Currently, the main cancers diagnosed are breast, lung, and colorectal. There is no standardized tool for cancer diagnoses; initially, clinical procedures are guided by the patient symptoms and usually involve biochemical blood tests, imaging, and biopsy. Label-free non-linear optical approaches are promising tools for tumor imaging, due to their inherent non-invasive biosafe contrast mechanisms and the ability to monitor collagen-related disorders, and biochemical and metabolic changes during cancer progression. In this review, the main non-linear microscopy techniques are discussed, according to three main contrast mechanisms: biochemical, metabolic, and structural imaging. Full article

► Show Figures

Figure 1

10 pages, 4001 KiB

Open AccessArticle

Resolution Improvement for Coherent Illumination Microscopy via Incident Light Phase Modulation

by Jinzhong Ling, Yangyang Li, Jinkun Guo, Xin Liu and Xiaorui Wang

Optics 2024, 5(4), 406-415; https://doi.org/10.3390/opt5040030 - 14 Oct 2024

In order to break the diffraction limit and improve the imaging resolution of optical microscope, in this article, we theoretically deduced the influence of phase difference on imaging resolution under coherent illumination. As the phase difference increased, the resolution improved gradually. Inspired by [...] Read more.

In order to break the diffraction limit and improve the imaging resolution of optical microscope, in this article, we theoretically deduced the influence of phase difference on imaging resolution under coherent illumination. As the phase difference increased, the resolution improved gradually. Inspired by this conclusion, a super-resolution optical imaging system based on phase modulation was proposed and simulated. An optical mask was designed to generate additional phase difference for the adjacent area at the sample’s surface, and the influence of its structural parameters was analyzed numerically. The simulation results preliminarily confirm the feasibility of this scheme, laying the foundation for a more optimal and comprehensive super-resolution imaging scheme. Due to its advantages of high resolution, a wide field of view, and being compatible, this non-fluorescence super-resolution imaging scheme is worthy of further research and application. Full article

► Show Figures

Figure 1

More Articles...

Submit to Optics Review for Optics

Journal Menu

Journal Browser

► Journal Browser

Highly Accessed Articles

View More...

Latest Books

More Books and Reprints...

E-Mail Alert

News

21 January 2025
Acknowledgment to the Reviewers of Optics in 2024

21 January 2025
MDPI’s Newly Launched Journals in December 2024

7 January 2025
MDPI INSIGHTS: The CEO's Letter #19 - Reflecting on 2024, Society Journals, OA Germany

More News & Announcements...

Topics

Propose a Topic

Topic in Applied Sciences, Optics, Sensors, Materials, Fibers, Photonics, Micromachines

Distributed Optical Fiber Sensors Topic Editors: Jian Li, Hao Wu, Giancarlo C. Righini, Zhe Ma, Yahui Wang
Deadline: 15 June 2025

Topic in Applied Sciences, Computation, Entropy, J. Imaging, Optics

Color Image Processing: Models and Methods (CIP: MM) Topic Editors: Giuliana Ramella, Isabella Torcicollo
Deadline: 30 July 2025

Conferences

Announce Your Conference

More Conferences...

Special Issues

Propose a Special Issue

Special Issue in Optics

Advanced Optical Imaging for Biomedicine Guest Editors: Li Lin, Zhiyi Liu
Deadline: 30 April 2025

Special Issue in Optics

Optical Network on Chip and Silicon Photonics Guest Editor: Meisam Abdollahi
Deadline: 31 May 2025

Special Issue in Optics

Advances in Biophotonics Using Optical Microscopy Techniques Guest Editor: Ellas Spyratou
Deadline: 30 June 2025

Special Issue in Optics

Optoelectronic Thin Films Guest Editors: Jigang Wang, Junming Li, Zhenjun Li, Tao Jiang, Meng Li
Deadline: 30 June 2025

Topical Collections

Topical Collection in Optics

Feature Paper Collection of Emerging Trends on Optics Collection Editors: Costantino De Angelis, Thomas Seeger

Back to TopTop