Journal Description
Optics
Optics
is an international, peer-reviewed, open access journal of optics published quarterly online by MDPI.
- Open Access—free to download, share, and reuse content. Authors receive recognition for their contribution when the paper is reused.
- Rapid Publication: manuscripts are peer-reviewed and a first decision provided to authors approximately 15.3 days after submission; acceptance to publication is undertaken in 2.9 days (median values for papers published in this journal in the first half of 2021).
- Recognition of Reviewers: APC discount vouchers, optional signed peer review, and reviewer names published annually in the journal.
Latest Articles
Micro-Machining of Diamond, Sapphire and Fused Silica Glass Using a Pulsed Nano-Second Nd:YVO4 Laser
Optics 2021, 2(3), 169-183; https://doi.org/10.3390/opt2030016 - 23 Aug 2021
Abstract
Optically transparent materials are being found in an ever-increasing array of technological applications within industries, such as automotive and communications. These industries are beginning to realize the importance of implementing surface engineering techniques to enhance the surface properties of materials. On account of
[...] Read more.
Optically transparent materials are being found in an ever-increasing array of technological applications within industries, such as automotive and communications. These industries are beginning to realize the importance of implementing surface engineering techniques to enhance the surface properties of materials. On account of the importance of surface engineering, this paper details the use of a relatively inexpensive diode-pumped solid state (DPSS) Nd:YVO4 laser to modify the surfaces of fused silica glass, diamond, and sapphire on a micrometre scale. Using threshold fluence analysis, it was identified that, for this particular laser system, the threshold fluence for diamond and sapphire ranged between 10 Jcm−2 and 35 Jcm−2 for a laser wavelength of 355 nm, dependent on the cumulative effects arising from the number of incident pulses. Through optical microscopy and scanning electron microscopy, it was found that the quality of processing resulting from the Nd:YVO4 laser varied with each of the materials. For fused silica glass, considerable cracking and deformation occurred. For sapphire, good quality features were produced, albeit with the formation of debris, indicating the requirement for post-processing to remove the observed debris. The diamond material gave rise to the best quality results, with extremely well defined micrometre features and minimal debris formation, comparative to alternative techniques such as femtosecond laser surface engineering.
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(This article belongs to the Special Issue Feature Papers in Optics)
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Study of Superoscillating Functions Application to Overcome the Diffraction Limit with Suppressed Sidelobes
Optics 2021, 2(3), 155-168; https://doi.org/10.3390/opt2030015 - 20 Aug 2021
Abstract
The problem of overcoming the diffraction limit does not have an unambiguously advantageous solution because of the competing nature of different beams’ parameters, such as the focal spot size, energy efficiency, and sidelobe level. The possibility to overcome the diffraction limit with suppressed
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The problem of overcoming the diffraction limit does not have an unambiguously advantageous solution because of the competing nature of different beams’ parameters, such as the focal spot size, energy efficiency, and sidelobe level. The possibility to overcome the diffraction limit with suppressed sidelobes out of the near-field zone using superoscillating functions was investigated in detail. Superoscillation is a phenomenon in which a superposition of harmonic functions contains higher spatial frequencies than any of the terms in the superposition. Two types of superoscillating one-dimensional signals were considered, and simulation of their propagation in the near diffraction zone based on plane waves expansion was performed. A comparative numerical study showed the possibility of overcoming the diffraction limit with a reduced level of sidelobes at a certain distance outside the zone of evanescent waves.
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(This article belongs to the Special Issue Feature Papers in Optics)
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A Preliminary Investigation on the Photothermal Properties of Luminescent Solar Concentrators
Optics 2021, 2(3), 148-154; https://doi.org/10.3390/opt2030014 - 05 Aug 2021
Abstract
Luminescent solar concentrators (LSCs) are considered promising photovoltaic (PV) devices to circumvent practical issues of applying conventional solar panels to the built environment. However, LSCs suffer from low power conversion efficiencies (PCEs) (typically <2% for devices of over 1 m2), despite
[...] Read more.
Luminescent solar concentrators (LSCs) are considered promising photovoltaic (PV) devices to circumvent practical issues of applying conventional solar panels to the built environment. However, LSCs suffer from low power conversion efficiencies (PCEs) (typically <2% for devices of over 1 m2), despite numerous efforts having been made to develop novel luminescent materials and optical techniques. In this report, we proposed to utilize photothermal (PT) energy of the LSCs to further improve the PCE. We conducted a preliminary investigation on the PV and PT properties of an LSC with dimensions of 300 mm × 300 mm × 5 mm. The results showed that the PT power (27.05 W) was much higher than the PV power (2.12 W). Further analysis indicated that the PCE could reach 3.41% for a device of 1 m2.
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(This article belongs to the Special Issue Novel Research on Solar Photothermal Technology: Theory, Design, System and Applications)
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Open AccessArticle
Biochemical Profiles of In Vivo Oral Mucosa by Using a Portable Raman Spectroscopy System
by
, , , and
Optics 2021, 2(3), 134-147; https://doi.org/10.3390/opt2030013 - 16 Jul 2021
Abstract
Most oral injuries are diagnosed by histopathological analysis of invasive and time-consuming biopsies. This analysis and conventional clinical observation cannot identify biochemically altered tissues predisposed to malignancy if no microstructural changes are detectable. With this in mind, detailed biochemical characterization of normal tissues
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Most oral injuries are diagnosed by histopathological analysis of invasive and time-consuming biopsies. This analysis and conventional clinical observation cannot identify biochemically altered tissues predisposed to malignancy if no microstructural changes are detectable. With this in mind, detailed biochemical characterization of normal tissues and their differentiation features on healthy individuals is important in order to recognize biomolecular changes associated with early tissue predisposition to malignant transformation. Raman spectroscopy is a label-free method for characterization of tissue structure and specific composition. In this study, we used Raman spectroscopy to characterize the biochemistry of in vivo oral tissues of healthy individuals. We investigated this biochemistry based on the vibrational modes related to Raman spectra of four oral subsites (buccal, gingiva, lip and tongue) of ten volunteers as well as with principal component (PC) loadings for the difference between the four types of oral subsites. Therefore, we determined the biochemical characteristics of each type of healthy oral subsite and those corresponding to differentiation of the four types of subsites. In addition, we developed a spectral reference of oral healthy tissues of individuals in the Brazilian population for future diagnosis of early pathological conditions using real-time, noninvasive and label-free techniques such as Raman spectroscopy.
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(This article belongs to the Special Issue New Discoveries in Biomedical Optical Imaging and Sensing: From Technologies to Applications)
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Refractometric Properties of a TFBG Sensor Demodulated Using α-Shape Modified Delaunay Triangulation
by
and
Optics 2021, 2(2), 113-133; https://doi.org/10.3390/opt2020012 - 09 Jun 2021
Abstract
In our previous research, a novel demodulation technique based on α-shape Delaunay triangulation (D-T) was developed to obtain the refractive index of the medium surrounding the optical fibre using the envelope of the cladding peaks from the spectrum of the tilted fibre Bragg
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In our previous research, a novel demodulation technique based on α-shape Delaunay triangulation (D-T) was developed to obtain the refractive index of the medium surrounding the optical fibre using the envelope of the cladding peaks from the spectrum of the tilted fibre Bragg grating (TFBG) sensor. This technique was demonstrated to be efficient, easy to implement, powerful, faster than the previous ones and applicable for real-time measurements. In this paper, a deep parametric analysis of the resolution, repeatability and accuracy of the D-T demodulation technique for a TFBG refractometer sensor is performed and presented. The spectral properties of the TFBG sensor as a refractometer are explored using the same demodulation technique. Specifically, supposing the use of the TFBG as a two-parameter optical sensor, the influence of the strain on the envelope area is analysed, and the measurement stability regarding the external RI is reported. Then, the cladding resonance peaks in the spectrum are observed experimentally as the TFBG undergoes partial immersion in a defined refractive index liquid. This last experiment allowed a better understanding the evolution of the TFBG transmission spectrum when the Bragg gratings were partially surrounded by a medium with a different RI.
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(This article belongs to the Special Issue Feature Papers in Optics)
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Design of Refractive/Diffractive Hybrid Projection Lens for DMD-Based Maskless Lithography
Optics 2021, 2(2), 103-112; https://doi.org/10.3390/opt2020011 - 08 Jun 2021
Abstract
The projection lens is the core component of DMD-based maskless lithography and its imaging quality directly affects the transferal of exposure pattern. Based on the traditional projection lens system, we have designed diffractive optical element (DOE) and aspheric surfaces to optimize the refractive/diffractive
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The projection lens is the core component of DMD-based maskless lithography and its imaging quality directly affects the transferal of exposure pattern. Based on the traditional projection lens system, we have designed diffractive optical element (DOE) and aspheric surfaces to optimize the refractive/diffractive hybrid projection lens system to improve its imaging quality. We found that the best effect is obtained when DOE is very close to the front lens group before the diaphragm of the hybrid system. Compared with the traditional projection lens system, this hybrid projection lens system has lower wave aberration with the help of DOE, and higher image quality owing to the modulation transfer function (MTF) value being improved. Finally, a hybrid projection lens system with working distance of 29.07 mm, image Space NA of 0.45, and total length of 196.97 mm is designed. We found that the maximum distortion and field curvature are 1.36 × 10−5% and 0.91 μm, respectively.
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(This article belongs to the Special Issue Fabrication and Applications of Photonic Micro-Devices)
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Modelling Dispersion Compensation in a Cascaded-Fiber-Feedback Optical Parametric Oscillator
Optics 2021, 2(2), 96-102; https://doi.org/10.3390/opt2020010 - 28 May 2021
Abstract
Fiber-feedback optical parametric oscillators (OPOs) incorporate intracavity fibers to provide a compact high-energy wavelength-tunable laser platform; however, dispersive effects can limit operation to the sub-picosecond regime. In this research article, we modeled pulse propagation through systems of cascaded fibers, incorporating SMF-28 and ultra-high
[...] Read more.
Fiber-feedback optical parametric oscillators (OPOs) incorporate intracavity fibers to provide a compact high-energy wavelength-tunable laser platform; however, dispersive effects can limit operation to the sub-picosecond regime. In this research article, we modeled pulse propagation through systems of cascaded fibers, incorporating SMF-28 and ultra-high numerical aperture (UHNA) fibers with complementary second-order dispersion coefficients. We found that the pulse duration upon exiting the fiber system is dominated by uncompensated third-order effects, with UHNA7 presenting the best opportunity to realise a cascaded-fiber-feedback OPO.
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(This article belongs to the Special Issue Recent Developments in Novel Solid State Lasers)
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Dual-Output Mode Analysis of Multimode Laguerre-Gaussian Beams via Deep Learning
by
, , , , , , , , , and
Optics 2021, 2(2), 87-95; https://doi.org/10.3390/opt2020009 - 24 May 2021
Abstract
The Laguerre-Gaussian (LG) beam demonstrates great potential for optical communication due to its orthogonality between different eigenstates, and has gained increased research interest in recent years. Here, we propose a dual-output mode analysis method based on deep learning that can accurately obtain both
[...] Read more.
The Laguerre-Gaussian (LG) beam demonstrates great potential for optical communication due to its orthogonality between different eigenstates, and has gained increased research interest in recent years. Here, we propose a dual-output mode analysis method based on deep learning that can accurately obtain both the mode weight and phase information of multimode LG beams. We reconstruct the LG beams based on the result predicted by the convolutional neural network. It shows that the correlation coefficient values after reconstruction are above 0.9999, and the mean absolute error (MAE) of the mode weights and phases are about 1.4 and 2.9 , respectively. The model still maintains relatively accurate prediction for the associated unknown data set and the noise-disturbed samples. In addition, the computation time of the model for a single test sample takes only 0.975 ms on average. These results show that our method has good abilities of generalization and robustness and allows for nearly real-time modal analysis.
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(This article belongs to the Special Issue Recent Developments in Optical Communications)
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A 100 Gbps OFDM-Based 28 GHz Millimeter-Wave Radio over Fiber Fronthaul System for 5G
Optics 2021, 2(2), 70-86; https://doi.org/10.3390/opt2020008 - 30 Apr 2021
Abstract
Due to the unprecedented growth in mobile data traffic, emerging mobile access networks such as fifth-generation (5G) would require huge bandwidth and a mobile fronthaul architecture as an essential solution in providing a high capacity for support in the future. To increase capacity,
[...] Read more.
Due to the unprecedented growth in mobile data traffic, emerging mobile access networks such as fifth-generation (5G) would require huge bandwidth and a mobile fronthaul architecture as an essential solution in providing a high capacity for support in the future. To increase capacity, utilizing millimeter waves (mm-waves) in an analog radio over fiber (RoF) fronthaul link is the major advancement and solution in achieving higher bandwidth and high data rate to cater for 5G mobile communication. In this paper, we demonstrate the feasibility of transmission and reception of a 100 Gbits/s data rate link at 28 GHz. The performance of three modulation formats (16-PSK, 16-QAM and 64-QAM) have been compared for an optical fiber length from 5 km up to 35 km for two detection systems; coherent and direct detection. Also, in this paper, the transmission impairments inherent to transmission systems are realized through the implementation of a digital signal processing (DSP) compensation scheme in the receiver system to enhance system performance. Quality factor (QF) and bit error rate (BER) are used as metrics to evaluate the system performance. The proposed system model is designed and simulated using Optisystem 16.
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(This article belongs to the Special Issue Recent Developments in Optical Communications)
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Research of Scattering Properties in Solid-Core Polarization-Maintaining Photonic Crystal Fibers
Optics 2021, 2(2), 63-69; https://doi.org/10.3390/opt2020007 - 26 Mar 2021
Abstract
The scattering from air–glass interfaces within solid-core polarization-maintaining photonic crystal fiber (PM–PCF) will increase the fiber attenuation coefficient, which may lead to high transmission loss. Therefore, it is necessary to describe scattering properties to guide research into reducing fiber loss. In this paper,
[...] Read more.
The scattering from air–glass interfaces within solid-core polarization-maintaining photonic crystal fiber (PM–PCF) will increase the fiber attenuation coefficient, which may lead to high transmission loss. Therefore, it is necessary to describe scattering properties to guide research into reducing fiber loss. In this paper, the loss resulting from roughness scattering at multi-hole interfaces within PM–PCF was theoretically and experimentally analyzed. A PM–PCF scattering model was established to explore the scattering distribution. On the other hand, a fully automatic testing device was built to enable the measurement of a three-dimensional scattering sphere. Simulations were in good agreement with experimental measurements. Moreover, this new proposed measurement method could apply to other PCFs and it will be a useful tool for further scattering research.
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(This article belongs to the Special Issue Fabrication and Applications of Photonic Micro-Devices)
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Prophylactic Corneal Cross-Linking in Myopic Femtosecond Laser-Assisted In Situ Keratomileusis: Long-Term Visual and Refractive Outcomes
by
, , , , , and
Optics 2021, 2(1), 55-62; https://doi.org/10.3390/opt2010006 - 15 Mar 2021
Abstract
The purpose of our study was to evaluate the safety, effectiveness, predictability, and stability of myopic and astigmatic laser-assisted in situ keratomileusis (LASIK) with simultaneous prophylactic corneal cross-linking (CXL) in thin corneas. In total, 100 eyes from 50 patients who were subjected to
[...] Read more.
The purpose of our study was to evaluate the safety, effectiveness, predictability, and stability of myopic and astigmatic laser-assisted in situ keratomileusis (LASIK) with simultaneous prophylactic corneal cross-linking (CXL) in thin corneas. In total, 100 eyes from 50 patients who were subjected to myopic and astigmatism femtosecond LASIK with simultaneous prophylactic CXL were included. The design of the study was retrospective, longitudinal, and observational. All patients had a 48-month follow-up. The MEL 80 excimer laser was utilized with the Aberration Smart Ablation platform. CXL treatment was applied when the predicted stromal thickness was less than 330 µm. Patients’ mean age was 30.22 ± 5.97 years. Previous mean spherical equivalent was −5.50 ± 1.65 (−9.50 to −1.13) diopters (D). Postoperative mean spherical equivalent was −0.24 ± 0.29 (−0.85 to +0.50) D. Visual acuity (VA) of 20/20 or better was observed in 87% of the eyes and no eyes experienced VA loss. Spherical equivalent within ±0.50 D was observed in 93% of eyes, and 4% of eyes varied by 0.50 D or more between 3 and 48 months. Prophylactic corneal cross-linking with simultaneous femtosecond laser-assisted in situ keratomileusis in thin corneas proved to be effective, safe, and predictable. The results remained stable after 48 months of follow-up.
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(This article belongs to the Special Issue Novel Research on Optometry and Vision Sciences)
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Open AccessEditorial
Acknowledgment to Reviewers of Optics in 2020
Optics 2021, 2(1), 54; https://doi.org/10.3390/opt2010005 - 01 Feb 2021
Abstract
Peer review is the driving force of journal development, and reviewers are gatekeepers who ensure that Optics maintains its standards for the high quality of its published papers [...]
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Nature of Photoelectric Effect in a Ge-on-Si SPAD at Ultralow Energy in Incident Pulsed Laser Radiation
Optics 2021, 2(1), 45-53; https://doi.org/10.3390/opt2010004 - 31 Jan 2021
Abstract
The photoelectric effect in a Ge-on-Si single-photon avalanche detector (SPAD) at an ultralow energy in incident pulsed laser radiation is considered in the frame of the classical theory of the electrodynamics of continuous media. It is shown that the energy of
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The photoelectric effect in a Ge-on-Si single-photon avalanche detector (SPAD) at an ultralow energy in incident pulsed laser radiation is considered in the frame of the classical theory of the electrodynamics of continuous media. It is shown that the energy of incident laser radiation which is shared among a huge number of electrons in a Ge matrix can concentrate on only one of these through the effect of the constructive interference of the fields re-emitted by surrounding electrons. Conservation of energy in this case is upheld because of a substantial narrowing of the effective bandgap in heavily doped p-Ge, which is used in the design of the SPAD considered.
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(This article belongs to the Special Issue Feature Papers in Optics)
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Towards Laser-Based Calibration-Free Quantification of Trace Elements
Optics 2021, 2(1), 43-44; https://doi.org/10.3390/opt2010003 - 04 Jan 2021
Abstract
It is told that Theodore Maiman called the first operating laser source he and his co-worker Charles Asawa realized 60 years ago [...]
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(This article belongs to the Special Issue Laser–Matter Interaction)
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Optimising the AR Engraved Structure on Light-Guide Facets for a Wide Range of Wavelengths
Optics 2021, 2(1), 25-42; https://doi.org/10.3390/opt2010002 - 31 Dec 2020
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The present study is aimed at designing anti-reflective (AR) engraving on the input–output surfaces of a rectangular light-guide. We estimate AR efficiency, by the transmittance level in the angular range, determined by the light-guide. Using nano-engraving, we achieve a uniform high transmission over
[...] Read more.
The present study is aimed at designing anti-reflective (AR) engraving on the input–output surfaces of a rectangular light-guide. We estimate AR efficiency, by the transmittance level in the angular range, determined by the light-guide. Using nano-engraving, we achieve a uniform high transmission over a wide range of wavelengths. In the past, we used smoothed conical pins or indentations on the faces of light-guide crystal as the engraved structure. Here, we widen the class of pins under consideration, following the physical model developed in the previous paper. We analyze the smoothed pyramidal pins with different base shapes. The possible effect of randomization of the pins parameters is also examined. The results obtained demonstrate optimized engraved structure with parameters depending on the required spectral range and facet format. The predicted level of transmittance is close to 99%, and its flatness (estimated by the standard deviation) in the required wavelengths range is 0.2%. The theoretical analysis and numerical calculations indicate that the obtained results demonstrate the best transmission (reflection) we can expect for a facet with the given shape and size for the required spectral band. The approach is equally useful for any other form and of the facet. We also discuss a simple way of comparing experimental and theoretical results for a light-guide with the designed input and output features. In this study, as well as in our previous work, we restrict ourselves to rectangular facets. We also consider the limitations on maximal transmission produced by the size and shape of the light-guide facets. The theoretical analysis is performed for an infinite structure and serves as an upper bound on the transmittance for smaller-size apertures.
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Open AccessReview
Signal and Image Processing in Biomedical Photoacoustic Imaging: A Review
Optics 2021, 2(1), 1-24; https://doi.org/10.3390/opt2010001 - 31 Dec 2020
Cited by 1
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Photoacoustic imaging (PAI) is a powerful imaging modality that relies on the PA effect. PAI works on the principle of electromagnetic energy absorption by the exogenous contrast agents and/or endogenous molecules present in the biological tissue, consequently generating ultrasound waves. PAI combines a
[...] Read more.
Photoacoustic imaging (PAI) is a powerful imaging modality that relies on the PA effect. PAI works on the principle of electromagnetic energy absorption by the exogenous contrast agents and/or endogenous molecules present in the biological tissue, consequently generating ultrasound waves. PAI combines a high optical contrast with a high acoustic spatiotemporal resolution, allowing the non-invasive visualization of absorbers in deep structures. However, due to the optical diffusion and ultrasound attenuation in heterogeneous turbid biological tissue, the quality of the PA images deteriorates. Therefore, signal and image-processing techniques are imperative in PAI to provide high-quality images with detailed structural and functional information in deep tissues. Here, we review various signal and image processing techniques that have been developed/implemented in PAI. Our goal is to highlight the importance of image computing in photoacoustic imaging.
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Open AccessArticle
Outdoor Visible Light Communication Channel Modeling under Smoke Conditions and Analogy with Fog Conditions
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, , , , and
Optics 2020, 1(3), 259-281; https://doi.org/10.3390/opt1030020 - 28 Nov 2020
Cited by 3
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Visible Light Communication (VLC) has gained popularity in research and business in the last decade. This technology aims to combine lighting and communication into a single device. For now, this technology has been thoroughly studied for an indoor environment, but it is sufficiently
[...] Read more.
Visible Light Communication (VLC) has gained popularity in research and business in the last decade. This technology aims to combine lighting and communication into a single device. For now, this technology has been thoroughly studied for an indoor environment, but it is sufficiently mature nowadays to consider its outdoor-environment potentials. The key outdoor challenges are the weather variabilities and smoke particles in cities due to pollution or fires. The aim of this is the study and quantification of the weather and smoke particles’ impact on a short-range optical communication thanks to a simulator. This article’s novelty is the inclusion of the effects of smoke in a short-range outdoor VLC system channel model. This smoke model, which comes from the fire engineering field, states that smoke attenuation is independent of the wavelength, starting from high visibility to 5 m. The visibility represents the distance up to which an object can be distinguished against the background. The effects of fog and smoke are studied in the case of two outdoor VLC scenarios. Smoke and fog models have analogous equations to express the optical attenuation they induce, using the visibility concept. Taking into account the actual light-emitting diode (LED) lamp radiation pattern, the simulator computes the power at the receiver side and the channel attenuation coefficients for a given fog or/and smoke outdoor setting. The main result drawn in this paper is that the channel attenuation levels due to fog and smoke are both in the same order of magnitude, starting from the visibility of about 1 km. The attenuation induced by fog is higher under this threshold of 1 km.
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Open AccessEditorial
Recent Development of Resonance-Based Optical Sensors and Biosensors
Optics 2020, 1(3), 255-258; https://doi.org/10.3390/opt1030019 - 28 Nov 2020
Cited by 4
Abstract
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(This article belongs to the Special Issue Recent Development of Resonance-Based Optical Sensors and Biosensors)
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Explanation of Photon Navigation in the Mach-Zehnder Interferometer
by
Optics 2020, 1(3), 243-254; https://doi.org/10.3390/opt1030018 - 28 Sep 2020
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Photons in interferometers manifest the functional ability to simultaneously navigate both paths through the device, but eventually appear at only one outlet. How this relates to the physical behaviour of the particle is still ambiguous, even though mathematical representation of the problem is
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Photons in interferometers manifest the functional ability to simultaneously navigate both paths through the device, but eventually appear at only one outlet. How this relates to the physical behaviour of the particle is still ambiguous, even though mathematical representation of the problem is adequate. This paper applies a non-local hidden-variable (NLHV) solution, in the form of the Cordus theory, to explain photon path dilemmas in the Mach–Zehnder (MZ) interferometer. The findings suggest that the partial mirrors direct the two reactive ends of the Cordus photon structures to different legs of the apparatus, depending on the energisation state of the photon. Explanations are provided for a single photon in the interferometer in the default, open-path, and sample modes. The apparent intelligence in the system is not because the photon knows which path to take, but rather because the MZ interferometer is a finely-tuned photon-sorting device that auto-corrects for randomness in the frequency phase to direct the photon to a specific detector. The principles also explain other tunnelling phenomena involving barriers. Thus, navigation dilemmas in the MZ interferometer may be explained in terms of physical realism after all.
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Open AccessReview
Optical Fibre Micro/Nano Tips as Fluorescence-Based Sensors and Interrogation Probes
by
, , , , , , , , , and
Optics 2020, 1(2), 213-242; https://doi.org/10.3390/opt1020017 - 27 Aug 2020
Cited by 3
Abstract
Optical fibre micro/nano tips (OFTs), defined here as tapered fibres with a waist diameter ranging from a few microns to tens of nanometres and different tip angles (i.e., from tens of degrees to fractions of degrees), represent extremely versatile tools that have attracted
[...] Read more.
Optical fibre micro/nano tips (OFTs), defined here as tapered fibres with a waist diameter ranging from a few microns to tens of nanometres and different tip angles (i.e., from tens of degrees to fractions of degrees), represent extremely versatile tools that have attracted growing interest during these last decades in many areas of photonics. The field of applications can range from physical and chemical/biochemical sensing—also at the intracellular levels—to the development of near-field probes for microscope imaging (i.e., scanning near-field optical microscopy (SNOM)) and optical interrogation systems, up to optical devices for trapping and manipulating microparticles (i.e., optical tweezers). All these applications rely on the ability to fabricate OFTs, tailoring some of their features according to the requirements determined by the specific application. In this review, starting from a short overview of the main fabrication methods used for the realisation of these optical micro/nano structures, the focus will be concentrated on some of their intriguing applications such as the development of label-based chemical/biochemical sensors and the implementation of SNOM probes for interrogating optical devices, including whispering gallery mode microcavities.
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(This article belongs to the Special Issue Recent Development of Resonance-Based Optical Sensors and Biosensors)
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