Optics

12 pages, 3271 KB

Open AccessEditor’s ChoiceArticle

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

Cited by 5 | Viewed by 2073

Abstract

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

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18 pages, 7213 KB

Open AccessEditor’s ChoiceReview

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 5 | Viewed by 3693

Abstract

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

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10 pages, 3124 KB

Open AccessEditor’s ChoiceCommunication

Multipolar Analysis in Symmetrical Meta-Atoms Sustaining Fano Resonances

by Vittorio Bonino and Angelo Angelini

Optics 2024, 5(2), 238-247; https://doi.org/10.3390/opt5020017 - 15 Apr 2024

Cited by 2 | Viewed by 1863

Abstract

We present an optical metasurface with symmetrical individual elements sustaining Fano resonances with high Q-factors. This study combines plane-wave illumination and modal analysis to investigate the resonant behavior that results in a suppression of the forward scattering, and we investigate the role of [...] Read more.

We present an optical metasurface with symmetrical individual elements sustaining Fano resonances with high Q-factors. This study combines plane-wave illumination and modal analysis to investigate the resonant behavior that results in a suppression of the forward scattering, and we investigate the role of the lattice constant on the excited multipoles and on the spectral position and Q-factor of the Fano resonances, revealing the nonlocal nature of the resonances. The results show that the intrinsic losses play a crucial role in modulating the resonance amplitude in specific conditions and that the optical behavior of the device is extremely sensitive to the pitch of the metasurface. The findings highlight the importance of near-neighbor interactions to achieve high Q resonances and offer an important tool for the design of spectrally tunable metasurfaces using simple geometries. Full article

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12 pages, 4893 KB

Open AccessEditor’s ChoiceArticle

Angle-Resolved Optical Characterization of a Plasmonic Triangular Array of Elliptical Holes in a Gold Layer

by Margherita Angelini, Konstantins Jefimovs, Paola Pellacani, Dimitrios Kazazis, Franco Marabelli and Francesco Floris

Optics 2024, 5(1), 195-206; https://doi.org/10.3390/opt5010014 - 21 Mar 2024

Cited by 4 | Viewed by 2314

Abstract

Plasmonic arrays are grating-like structures able to couple an incoming electromagnetic field into either localized or propagating surface plasmonic modes. A triangular array of elliptical holes in a gold layer were realized resorting to displacement Talbot lithography. Scanning electron microscopy was used to [...] Read more.

Plasmonic arrays are grating-like structures able to couple an incoming electromagnetic field into either localized or propagating surface plasmonic modes. A triangular array of elliptical holes in a gold layer were realized resorting to displacement Talbot lithography. Scanning electron microscopy was used to evaluate the geometrical features and finite time domain simulations were performed to verify the consistency of the design. The optical response was characterized by angle-resolved reflectance and transmittance measurements. The results demonstrate the good quality and uniformity of the array. Furthermore, the study on the dependence of the optical response on both the hexagonal lattice and the elliptical hole-defined symmetry properties was conducted allowing the distinction of their effects on both the localized and propagating plasmonic modes. The results indicate that the localized component of the plasmonic modes is mainly affected by the elliptical shape, while the propagating part is influenced by the hexagonal lattice symmetry. Full article

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11 pages, 3128 KB

Open AccessEditor’s ChoiceArticle

Nanofabrication Process Scale-Up via Displacement Talbot Lithography of a Plasmonic Metasurface for Sensing Applications

by Paola Pellacani, Konstantins Jefimovs, Margherita Angelini, Franco Marabelli, Valentina Tolardo, Dimitrios Kazazis and Francesco Floris

Optics 2024, 5(1), 165-175; https://doi.org/10.3390/opt5010012 - 8 Mar 2024

Cited by 2 | Viewed by 2992

Abstract

The selection of an affordable method to fabricate plasmonic metasurfaces needs to guarantee complex control over both tunability and reproducibility of their spectral and morphological properties, making plasmonic metasurfaces suitable for integration into different sensing devices. Displacement Talbot lithography could be a valid [...] Read more.

The selection of an affordable method to fabricate plasmonic metasurfaces needs to guarantee complex control over both tunability and reproducibility of their spectral and morphological properties, making plasmonic metasurfaces suitable for integration into different sensing devices. Displacement Talbot lithography could be a valid solution thanks to the limited fabrication steps required, also providing the highly desired industrial scalability. Fabricated plasmonic metasurfaces are represented by a gold nanohole array on a glass substrate based on a triangular pattern. Scanning electron microscopy measurements have been recorded, showing the consistency of the surface features with the optimized design parameters. Reflectance and transmittance measurements have also been carried out to test the reliability and standardization of the metasurface’s optical response. Furthermore, these plasmonic metasurfaces have also been successfully tested for probing refractive index variations in a microfluidic system, paving the way for their use in sensitive, real-time, label-free, and multiplexing detection of bio-molecular events. Full article

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12 pages, 4561 KB

Open AccessEditor’s ChoiceArticle

Design of Planar Multilayer Devices for Optical Filtering Using Surrogate Model Based on Artificial Neural Network

by Davi F. Rêgo, Fabrício G. S. Silva, Rodrigo C. Gusmão and Vitaly F. Rodriguez-Esquerre

Optics 2024, 5(1), 121-132; https://doi.org/10.3390/opt5010009 - 1 Mar 2024

Cited by 2 | Viewed by 2123

Abstract

Artificial intelligence paradigms hold significant potential to advance nanophotonics. This study presents a novel approach to designing a plasmonic absorber using an artificial neural network as a surrogate model in conjunction with a genetic algorithm. The methodology involved numerical simulations of multilayered metal–dielectric [...] Read more.

Artificial intelligence paradigms hold significant potential to advance nanophotonics. This study presents a novel approach to designing a plasmonic absorber using an artificial neural network as a surrogate model in conjunction with a genetic algorithm. The methodology involved numerical simulations of multilayered metal–dielectric plasmonic structures to establish a dataset for training an artificial neural network (ANN). The results demonstrate the proficiency of the trained ANN in predicting reflectance spectra and its ability to generalize intricate relationships between desired performance and geometric configurations, with values of correlation higher than 98% in comparison with ground-truth electromagnetic simulations. Furthermore, the ANN was employed as a surrogate model in a genetic algorithm (GA) loop to achieve target optical behaviors. The proposed methodology provides a powerful means of inverse designing multilayered metal–dielectric devices tailored for visible band wavelength filtering. This research demonstrates that the integration of AI-driven approaches in nanophotonics leads to efficient and effective design strategies. Full article

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

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13 pages, 4169 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Electronic Population Reconstruction from Strong-Field-Modified Absorption Spectra with a Convolutional Neural Network

by Daniel Richter, Alexander Magunia, Marc Rebholz, Christian Ott and Thomas Pfeifer

Optics 2024, 5(1), 88-100; https://doi.org/10.3390/opt5010007 - 26 Feb 2024

Cited by 1 | Viewed by 2369

Abstract

We simulate ultrafast electronic transitions in an atom and corresponding absorption line changes with a numerical, few-level model, similar to previous work. In addition, a convolutional neural network (CNN) is employed for the first time to predict electronic state populations based on the [...] Read more.

We simulate ultrafast electronic transitions in an atom and corresponding absorption line changes with a numerical, few-level model, similar to previous work. In addition, a convolutional neural network (CNN) is employed for the first time to predict electronic state populations based on the simulated modifications of the absorption lines. We utilize a two-level and four-level system, as well as a variety of laser-pulse peak intensities and detunings, to account for different common scenarios of light–matter interaction. As a first step towards the use of CNNs for experimental absorption data in the future, we apply two different noise levels to the simulated input absorption data. Full article

(This article belongs to the Special Issue Ultrafast Light-Matter Interaction)

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12 pages, 4523 KB

Open AccessEditor’s ChoiceArticle

Dual-Band Image Fusion Approach Using Regional Weight Analysis Combined with a Multi-Level Smoothing Filter

by Jia Yi, Huilin Jiang, Xiaoyong Wang and Yong Tan

Optics 2024, 5(1), 76-87; https://doi.org/10.3390/opt5010006 - 21 Feb 2024

Cited by 2 | Viewed by 1944

Abstract

Image fusion is an effective and efficient way to express the feature information of an infrared image and abundant detailed information of a visible image in a single fused image. However, obtaining a fused result with good visual effect, while preserving and inheriting [...] Read more.

Image fusion is an effective and efficient way to express the feature information of an infrared image and abundant detailed information of a visible image in a single fused image. However, obtaining a fused result with good visual effect, while preserving and inheriting those characteristic details, seems a challenging problem. In this paper, by combining a multi-level smoothing filter and regional weight analysis, a dual-band image fusion approach is proposed. Firstly, a series of dual-band image layers with different details are obtained using smoothing results. With different parameters in a bilateral filter, different smoothed results are achieved at different levels. Secondly, regional weight maps are generated for each image layer, and then we fuse the dual-band image layers with their corresponding regional weight map. Finally, by imposing proper weights, those fused image layers are synthetized. Through comparison with seven excellent fusion methods, both subjective and objective evaluations for the experimental results indicate that the proposed approach can produce the best fused image, which has the best visual effect with good contrast, and those small details are preserved and highlighted, too. In particular, for the image pairs with a size of 640 × 480, the algorithm could provide a good visual effect result within 2.86 s, and the result has almost the best objective metrics. Full article

(This article belongs to the Section Engineering Optics)

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10 pages, 2496 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Introducing Optical Nonlinearity in PDMS Using Organic Solvent Swelling

by Sudhakara Reddy Bongu, Maximilian Buchmüller, Daniel Neumaier and Patrick Görrn

Optics 2024, 5(1), 66-75; https://doi.org/10.3390/opt5010005 - 15 Feb 2024

Cited by 5 | Viewed by 3290

Abstract

The feasibility of introducing optical nonlinearity in poly-dimethyl siloxane (PDMS) using organic solvent swelling was investigated. The third-order nonlinear refraction and absorption properties of the individual materials, as well as the PDMS/solvent compounds after swelling were characterized. The well-established Z-scan technique served as [...] Read more.

The feasibility of introducing optical nonlinearity in poly-dimethyl siloxane (PDMS) using organic solvent swelling was investigated. The third-order nonlinear refraction and absorption properties of the individual materials, as well as the PDMS/solvent compounds after swelling were characterized. The well-established Z-scan technique served as characterization method for the nonlinear properties under picosecond pulsed laser excitation at a 532 nm wavelength. These experiments included investigations on the organic solvents nitrobenzene, 2,6-lutidine, and toluene, which showed inherent optical nonlinearity. We showed that nitrobenzene, one of the most well-known nonlinear optical materials, has proven suboptimal in this context due to its limited swelling effect in PDMS and comparatively high (non)linear absorption, resulting in undesirable thermal effects and potential photo-induced damage in the composite material. Toluene and 2,6-lutidine not only exhibited lower absorption compared to nitrobenzene but also show a more pronounced swelling effect in PDMS. The incorporation of toluene caused a weight change of up to 116% of PDMS, resulting in substantial nonlinear optical effects, reflected in the nonlinear refractive index of the PDMS/toluene composite

n_{2} = 3.1 \times 10^{- 15} {c m}^{2} / W

. Full article

(This article belongs to the Section Nonlinear Optics)

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12 pages, 4498 KB

Open AccessEditor’s ChoiceArticle

An Anti-Noise-Designed Residual Phase Unwrapping Neural Network for Digital Speckle Pattern Interferometry

by Biao Wang, Xiaoling Cao, Meiling Lan, Chang Wu and Yonghong Wang

Optics 2024, 5(1), 44-55; https://doi.org/10.3390/opt5010003 - 19 Jan 2024

Cited by 4 | Viewed by 2839

Abstract

DSPI (Digital Speckle Pattern Interferometry) is a non-destructive optical measurement technique that obtains phase information of an object through phase unwrapping. Traditional phase unwrapping algorithms depend on the quality of the images, which demands preprocessing such as filtering and denoising. Moreover, the unwrapping [...] Read more.

DSPI (Digital Speckle Pattern Interferometry) is a non-destructive optical measurement technique that obtains phase information of an object through phase unwrapping. Traditional phase unwrapping algorithms depend on the quality of the images, which demands preprocessing such as filtering and denoising. Moreover, the unwrapping time is highly influenced by the size of the images. In this study, we proposed a new deep learning-based phase unwrapping algorithm combining the residual network and U-Net network. Additionally, we incorporated an improved SSIM function as the loss function based on camera characteristics. The experimental results demonstrated that the proposed method achieved higher quality in highly noisy phase unwrapping maps compared to traditional algorithms, with SSIM values consistently above 0.98. In addition, we applied image stitching to the network to process maps of various sizes and the unwrapping time remained around 1 s even for larger images. In conclusion, our proposed network is able to achieve efficient and accurate phase unwrapping. Full article

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13 pages, 18048 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Investigating Laser-Induced Periodic Surface Structures (LIPSS) Formation in Silicon and Their Impact on Surface-Enhanced Raman Spectroscopy (SERS)

by Hardik Vaghasiya and Paul-Tiberiu Miclea

Optics 2023, 4(4), 538-550; https://doi.org/10.3390/opt4040039 - 19 Oct 2023

Cited by 24 | Viewed by 7062

Abstract

Laser-induced periodic surface structures (LIPSS) have gained significant attention due to their ability to modify the surface morphology of materials at the micro-nanoscale and show great promise for surface functionalization applications. In this study, we specifically investigate the formation of LIPSS in silicon [...] Read more.

Laser-induced periodic surface structures (LIPSS) have gained significant attention due to their ability to modify the surface morphology of materials at the micro-nanoscale and show great promise for surface functionalization applications. In this study, we specifically investigate the formation of LIPSS in silicon substrates and explore their impact on surface-enhanced Raman spectroscopy (SERS) applications. This study reveals a stepwise progression of LIPSS formation in silicon, involving three distinct stages of LIPSS: (1) integrated low-spatial-frequency LIPSS (LSFL) and high-spatial-frequency LIPSS (HSFL), (2) principally LSFL and, (3) LSFL at the edge of the irradiated spot, elucidating the complex interplay between laser fluence, pulse number, and resulting surface morphology. Furthermore, from an application standpoint, these high-quality multi-scale periodic patterns lead to the next step of texturing the entire silicon surface with homogeneous LIPSS for SERS application. The potential of LIPSS-fabricated silicon substrates for enhancing SERS performance is investigated using thiophenol as a test molecule. The results indicate that the Au-coated combination of LSFL and HSFL substrates showcased the highest enhancement factor (EF) of

1.38 \times 10^{6}

. This pronounced enhancement is attributed to the synergistic effects of localized surface plasmon resonance (LSPR) and surface plasmon polaritons (SPPs), intricately linked to HSFL and LSFL characteristics. These findings contribute to our understanding of LIPSS formation in silicon and their applications in surface functionalization and SERS, paving the way for sensing platforms. Full article

(This article belongs to the Special Issue Laser-Assisted Micro- and Nano-Fabrications)

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11 pages, 2803 KB

Open AccessEditor’s ChoiceArticle

Advanced Raman Spectroscopy Based on Transfer Learning by Using a Convolutional Neural Network for Personalized Colorectal Cancer Diagnosis

by Dimitris Kalatzis, Ellas Spyratou, Maria Karnachoriti, Maria Anthi Kouri, Spyros Orfanoudakis, Nektarios Koufopoulos, Abraham Pouliakis, Nikolaos Danias, Ioannis Seimenis, Athanassios G. Kontos and Efstathios P. Efstathopoulos

Optics 2023, 4(2), 310-320; https://doi.org/10.3390/opt4020022 - 27 Apr 2023

Cited by 16 | Viewed by 4206

Abstract

Advanced Raman spectroscopy (RS) systems have gained new interest in the field of medicine as an emerging tool for in vivo tissue discrimination. The coupling of RS with artificial intelligence (AI) algorithms has given a boost to RS to analyze spectral data in [...] Read more.

Advanced Raman spectroscopy (RS) systems have gained new interest in the field of medicine as an emerging tool for in vivo tissue discrimination. The coupling of RS with artificial intelligence (AI) algorithms has given a boost to RS to analyze spectral data in real time with high specificity and sensitivity. However, limitations are still encountered due to the large amount of clinical data which are required for the pre-training process of AI algorithms. In this study, human healthy and cancerous colon specimens were surgically resected from different sites of the ascending colon and analyzed by RS. Two transfer learning models, the one-dimensional convolutional neural network (1D-CNN) and the 1D–ResNet transfer learning (1D-ResNet) network, were developed and evaluated using a Raman open database for the pre-training process which consisted of spectra of pathogen bacteria. According to the results, both models achieved high accuracy of 88% for healthy/cancerous tissue discrimination by overcoming the limitation of the collection of a large number of spectra for the pre-training process. This gives a boost to RS as an adjuvant tool for real-time biopsy and surgery guidance. Full article

(This article belongs to the Special Issue Advances in Biophotonics Using Optical Microscopy Techniques)

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8 pages, 4732 KB

Open AccessEditor’s ChoiceArticle

Direct Laser Writing of Computer-Generated Holograms by Photodissolution of Silver in Arsenic Trisulfide

by Arjun Karimbana Kandy, Cedric Sebastien Martins Figueiredo, Manuel Fernandez Merino, Antoine Bourgade, Jean-Yves Natoli, Konstantinos Iliopoulos and Julien Lumeau

Optics 2023, 4(1), 138-145; https://doi.org/10.3390/opt4010010 - 31 Jan 2023

Cited by 8 | Viewed by 2423

Abstract

Photodissolution is a process that is well known for its ability to cause inclusion of silver into the matrix of a chalcogenide layer, changing its optical properties. In this paper, using e-beam deposition, we developed Ag (74 nm)/As₂S₃ (355 nm) [...] Read more.

Photodissolution is a process that is well known for its ability to cause inclusion of silver into the matrix of a chalcogenide layer, changing its optical properties. In this paper, using e-beam deposition, we developed Ag (74 nm)/As₂S₃ (355 nm) bilayers and characterized the photodissolution kinetics when exposed to actinic radiation. We showed that local complete silver photodissolution at the micron scale can be achieved. Based on this result, we then developed amplitude-based computer-generated holograms using direct laser writing. CW lasers with beam shaping and short pulse lasers with beam scanning were both implemented. Elements with 8.5 µm and <1 µm spatial resolution and close to theoretical intensity distribution, respectively, were successfully demonstrated. Full article

(This article belongs to the Special Issue Laser-Assisted Micro- and Nano-Fabrications)

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26 pages, 4059 KB

Open AccessFeature PaperEditor’s ChoiceReview

Gold Nanoparticles as Contrast Agents in Ophthalmic Imaging

by Alexandra Kavalaraki, Ellas Spyratou, Maria Anthi Kouri and Efstathios P. Efstathopoulos

Optics 2023, 4(1), 74-99; https://doi.org/10.3390/opt4010007 - 18 Jan 2023

Cited by 23 | Viewed by 6523

Abstract

Over the past few years, tremendous research concerning the possibilities of gold nanoparticles in medicine has been conducted. Gold nanoparticles (AuNPs) are considered to be unique nanostructures due to their extraordinary chemical and physical properties. This review article aims to bring into light [...] Read more.

Over the past few years, tremendous research concerning the possibilities of gold nanoparticles in medicine has been conducted. Gold nanoparticles (AuNPs) are considered to be unique nanostructures due to their extraordinary chemical and physical properties. This review article aims to bring into light the potential applications of gold nanoparticles for diagnostic purposes in ophthalmology. More specifically, attention will be drawn to the utilization of AuNPs as contrast agents (CAs) in optical coherence tomography (OCT) and photoacoustic imaging (PAI), which are two novel imaging modalities for the visualization of the eye. None of these techniques requires the use of an imaging adjuvant to function; however, the addition of a contrast agent has been proposed for image improvement, and AuNPs are attractive candidates for this purpose. The in vitro, ex vivo, and in vivo studies investigating and supporting this concept will be presented thoroughly to elucidate whether AuNPs are eligible for imaging enhancement owing to their optical characteristics. Full article

(This article belongs to the Special Issue Advances in Biophotonics Using Optical Microscopy Techniques)

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10 pages, 3150 KB

Open AccessEditor’s ChoiceArticle

A Multi-Spectral Thermal Gas Detection Imager Using Uncooled Infrared Camera

by Fang-Xiao Cui, Yue Zhao, An-Jing Wang, Feng-Xiang Ma, Jun Wu, Yang-Yu Li, Da-Cheng Li and Wang-Chao Dong

Optics 2022, 3(4), 473-482; https://doi.org/10.3390/opt3040040 - 12 Dec 2022

Cited by 10 | Viewed by 4392

Abstract

Gas remote detection is useful for early warning of gas leakage and toxic chemicals. Optical gas imaging (OGI) built with an uncooled infrared camera is superior to cooled detectors in terms of cost. Current mainstream OGI technologies fall short in their detection of [...] Read more.

Gas remote detection is useful for early warning of gas leakage and toxic chemicals. Optical gas imaging (OGI) built with an uncooled infrared camera is superior to cooled detectors in terms of cost. Current mainstream OGI technologies fall short in their detection of gases at ambient temperature and their ability to classify multiple gases. A multi-spectral uncooled imager is developed to try to solve these problems, which is constructed from a commercial uncooled thermal camera and wide band filters. To solve filter self-radiation and unevenness, a correction method is devised, with an ambient temperature blackbody placed in front and subtracted from the measured image. Based on waveband cutoffs, filters are classified into target-sensitive filters and background filters. Multi-spectra are simulated according to wide band filter transmittance, which can be used in gas classification. A sulfur hexafluoride (SF6) experiment is conducted outdoors at a distance of 10 m. An SVM model is trained to classify gas release in real time. Detection with a cold sky background is improved with the aid of data cube differences in a time sequence. The SF6 outdoor experiment concluded with preliminary effective results of ambient temperature gas remote detection. Full article

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21 pages, 349 KB

Open AccessEditor’s ChoiceArticle

Improving Early Optics Instruction Using a Phenomenological Approach: A Field Study

by Kai Fliegauf, Janika Sebald, Joaquin Marc Veith, Henrike Spiecker and Philipp Bitzenbauer

Optics 2022, 3(4), 409-429; https://doi.org/10.3390/opt3040035 - 9 Nov 2022

Cited by 8 | Viewed by 4315

Abstract

Previous research has shown that phenomenological approaches in early optics education might be superior to traditional model-based instruction based on the light ray realm with regards to fostering students’ conceptual understanding of basic optics topics. However, it remains open to date which learning [...] Read more.

Previous research has shown that phenomenological approaches in early optics education might be superior to traditional model-based instruction based on the light ray realm with regards to fostering students’ conceptual understanding of basic optics topics. However, it remains open to date which learning difficulties students encounter when being introduced to optics following a phenomenological approach—in particular, in comparison to the learning difficulties that are widespread among students introduced to optics via traditional model-based instruction. With this article, we contribute to closing this gap: We report the results of a quasi-experimental field study with

N = 189

secondary school students. We used ten items adapted from the literature in a pre-posttest design for an in-depth exploration of the conceptions of introductory optics topics acquired by

N = 89

students introduced to optics following a phenomenological teaching-learning sequence and compare these students’ conceptions to the ones acquired by

N = 100

peers who participated in traditional model-based instruction covering the same content topics. The results of this study substantiate earlier findings according to which phenomenological teaching might be a fruitful endeavour for early optics education, in particular, when it comes to teaching and learning about image formation by converging lenses. Full article

(This article belongs to the Special Issue Optics and Photonics: Technologies, Methods and Facilities in the 21st Century Teaching)

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19 pages, 365 KB

Open AccessEditor’s ChoiceReview

Selected Concepts of Quantum State Tomography

by Artur Czerwinski

Optics 2022, 3(3), 268-286; https://doi.org/10.3390/opt3030026 - 25 Aug 2022

Cited by 12 | Viewed by 7336

Abstract

Quantum state tomography (QST) refers to any method that allows one to reconstruct the accurate representation of a quantum system based on data obtainable from an experiment. In this paper, we concentrate on theoretical methods of quantum tomography, but some significant experimental results [...] Read more.

Quantum state tomography (QST) refers to any method that allows one to reconstruct the accurate representation of a quantum system based on data obtainable from an experiment. In this paper, we concentrate on theoretical methods of quantum tomography, but some significant experimental results are also presented. Due to a considerable body of literature and intensive ongoing research activity in the field of QST, this overview is restricted to presenting selected ideas, methods, and results. First, we discuss tomography of pure states by distinguishing two aspects—complex vector reconstruction and wavefunction measurement. Then, we move on to the Wigner function reconstruction. Finally, the core section of the article is devoted to the stroboscopic tomography, which provides the optimal criteria for state recovery by including the dynamics in the scheme. Throughout the paper, we pay particular attention to photonic tomography, since multiple protocols in quantum optics require well-defined states of light. Full article

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

9 pages, 745 KB

Open AccessEditor’s ChoiceArticle

Optical Properties of Tungsten: A Parametric Study to Characterize the Role of Roughness, Surface Composition and Temperature

by Federica Pappalardo, Francisco Romero Lairado, Cyprien Louis de Canonville, Céline Martin, Gregory Giacometti, Guillaume Serin, Eric Salomon, Thierry Angot, Laurent Gallais, Régis Bisson and Marco Minissale

Optics 2022, 3(3), 216-224; https://doi.org/10.3390/opt3030021 - 5 Jul 2022

Cited by 11 | Viewed by 4210

Abstract

Tungsten (W) is the material selected for the divertor exhaust of the international nuclear fusion experiment ITER. In this harsh environment, the interactions of heat loads and ion fluxes with W can induce temporary or permanent evolution in the optical properties. Poor knowledge [...] Read more.

Tungsten (W) is the material selected for the divertor exhaust of the international nuclear fusion experiment ITER. In this harsh environment, the interactions of heat loads and ion fluxes with W can induce temporary or permanent evolution in the optical properties. Poor knowledge of such evolution during a plasma operation can lead to errors in temperature measurements performed by optical diagnostics. Therefore, it is of fundamental importance to characterize possible changes in W optical properties. In this work, we studied the role of morphology and temperature on the optical response of W. The reflectivities of five W samples with different roughness values (20–100 nm) were measured during laser annealing (25–800 °C) in the visible and near-infrared domains (500–1100 nm). We observed an increase in reflectivity after annealing and we demonstrated that it was due to a change in the chemical composition of the surface, in particular a reduction in the amount of native oxide. Moreover, we show that roughness does not sensibly vary in the investigated temperature range. By highlighting the role played by roughness and surface impurities (e.g., oxide), we provide insight in how W optical properties can evolve in tokamaks where high ion fluxes, heat loads, and impurities can induce the evolution of both the morphology and surface composition of W. Full article

(This article belongs to the Special Issue Laser–Matter Interaction)

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18 pages, 7057 KB

Open AccessEditor’s ChoiceArticle

Photonic and Optomechanical Thermometry

by Tristan Briant, Stephan Krenek, Andrea Cupertino, Ferhat Loubar, Rémy Braive, Lukas Weituschat, Daniel Ramos, Maria Jose Martin, Pablo A. Postigo, Alberto Casas, René Eisermann, Daniel Schmid, Shahin Tabandeh, Ossi Hahtela, Sara Pourjamal, Olga Kozlova, Stefanie Kroker, Walter Dickmann, Lars Zimmermann, Georg Winzer, Théo Martel, Peter G. Steeneken, Richard A. Norte and Stéphan Briaudeau Show full author list Hide full author list

Optics 2022, 3(2), 159-176; https://doi.org/10.3390/opt3020017 - 29 Apr 2022

Cited by 10 | Viewed by 6077

Abstract

Temperature is one of the most relevant physical quantities that affects almost all processes in nature. However, the realization of accurate temperature standards using current temperature references, like the triple point of water, is difficult due to the requirements on material purity and [...] Read more.

Temperature is one of the most relevant physical quantities that affects almost all processes in nature. However, the realization of accurate temperature standards using current temperature references, like the triple point of water, is difficult due to the requirements on material purity and stability of the environment. In addition, in harsh environments, current temperature sensors with electrical readout, like platinum resistors, are difficult to implement, urging the development of optical temperature sensors. In 2018, the European consortium Photoquant, consisting of metrological institutes and academic partners, started investigating new temperature standards for self-calibrated, embedded optomechanical sensor applications, as well as optimised high resolution and high reliability photonic sensors, to measure temperature at the nano and meso-scales and as a possible replacement for the standard platinum resistant thermometers. This article presents an overview of the results obtained with sensor prototypes that exploit photonic and optomechanical techniques for sensing temperatures over a large temperature range (5 K to 300 K). Different concepts are demonstrated, including ring resonators, ladder-like resonators and suspended membrane optomechanical thermometers, highlighting initial performance and challenges, like self-heating that need to be overcome to realize photonic and optomechanical thermometry applications. Full article

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12 pages, 963 KB

Open AccessEditor’s ChoiceArticle

Resolution Limit of Correlation Plenoptic Imaging between Arbitrary Planes

by Francesco Scattarella, Milena D’Angelo and Francesco V. Pepe

Optics 2022, 3(2), 138-149; https://doi.org/10.3390/opt3020015 - 12 Apr 2022

Cited by 10 | Viewed by 2655

Abstract

Correlation plenoptic imaging (CPI) is an optical imaging technique based on intensity correlation measurement, which enables detecting, within fundamental physical limits, both the spatial distribution and the direction of light in a scene. This provides the possibility to perform tasks such as three-dimensional [...] Read more.

Correlation plenoptic imaging (CPI) is an optical imaging technique based on intensity correlation measurement, which enables detecting, within fundamental physical limits, both the spatial distribution and the direction of light in a scene. This provides the possibility to perform tasks such as three-dimensional reconstruction and refocusing of different planes. Compared with standard plenoptic imaging devices, based on direct intensity measurement, CPI overcomes the problem of the strong trade-off between spatial and directional resolution. Here, we study the resolution limit in a recent development of the technique, called correlation plenoptic imaging between arbitrary planes (CPI-AP). The analysis, based on Gaussian test objects, highlights the main properties of the technique, as compared with standard imaging, and provides an analytical guideline to identify the limits at which an object can be considered resolved. Full article

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