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Optics
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Feature Papers in Optics
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Feature Papers in Optics

A special issue of Optics (ISSN 2673-3269).

Deadline for manuscript submissions: closed (31 December 2021) | Viewed by 19824

Special Issue Editors

Prof. Dr. Costantino De Angelis

E-Mail Website
Guest Editor
Department of Information Engineering, University of Brescia, Piazza del Mercato, 15, 25121 Brescia, BS, Italy
Interests: integrated optics; plasmonics; optical antennas; nonlinear optics; microwaves; energy harvesting; photonics; telecommunications
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Thomas Seeger

E-Mail Website
Guest Editor
Institut Fluid- und Thermodynamik, Lehrstuhl für Technische Thermodynamik, Universität Siegen, Paul-Bonatz-Straße 9-11, 57076 Siegen, Germany
Interests: development and application of new laser diagnostic techniques as measurement tools for reacting flows (Mie, Rayleigh, Raman, CARS)
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues, 

This Special Issue of Optics will be comprised of a collection of top-quality papers published free of charge in open access form by Editorial Board Members, or those invited by the editorial office and the Editors-in-Chief. The papers should be long research papers (or review papers) with a full and detailed summary of the author's own work completed so far.

Prof. Dr. Costantino De Angelis
Prof. Dr. Thomas Seeger
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Optics is an international peer-reviewed open access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1200 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Published Papers (6 papers)

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Research

12 pages, 3509 KiB  
Article
Interferometric Ice Particle Imaging in a Wind Tunnel
by Mohamed Talbi, Romain Duperrier, Barbara Delestre, Gilles Godard and Marc Brunel
Optics 2021, 2(4), 216-227; https://0-doi-org.brum.beds.ac.uk/10.3390/opt2040020 - 05 Oct 2021
Cited by 4 | Viewed by 2315
Abstract
We report interferometric ice particle imaging and sizing in an icing wind tunnel with wind speeds of 70 m/s. Single particle interferograms are first analysed, size measurements are performed, and examples of possible reconstructed shapes are deduced from the interferometric images. Particle sizing [...] Read more.
We report interferometric ice particle imaging and sizing in an icing wind tunnel with wind speeds of 70 m/s. Single particle interferograms are first analysed, size measurements are performed, and examples of possible reconstructed shapes are deduced from the interferometric images. Particle sizing is also performed in the case of ice particles whose out-of-focus images overlap, with or without Moiré phenomena. Results show that the IPI technique can be carried out for irregular rough particles in a critical environment such as in an icing wind tunnel with high wind speeds. Full article
(This article belongs to the Special Issue Feature Papers in Optics)
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8 pages, 955 KiB  
Article
High Quality Factor Silicon Membrane Metasurface for Intensity-Based Refractive Index Sensing
by Andrea Tognazzi, Davide Rocco, Marco Gandolfi, Andrea Locatelli, Luca Carletti and Costantino De Angelis
Optics 2021, 2(3), 193-199; https://0-doi-org.brum.beds.ac.uk/10.3390/opt2030018 - 06 Sep 2021
Cited by 23 | Viewed by 5688
Abstract
We propose a new sensing device based on all-optical nano-objects placed in a suspended periodic array. We demonstrate that the intensity-based sensing mechanism can measure environment refractive index change of the order of 1.8×10−6, which is close to [...] Read more.
We propose a new sensing device based on all-optical nano-objects placed in a suspended periodic array. We demonstrate that the intensity-based sensing mechanism can measure environment refractive index change of the order of 1.8×10−6, which is close to record efficiencies in plasmonic devices. Full article
(This article belongs to the Special Issue Feature Papers in Optics)
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15 pages, 7399 KiB  
Article
Micro-Machining of Diamond, Sapphire and Fused Silica Glass Using a Pulsed Nano-Second Nd:YVO4 Laser
by David G. Waugh and Chris D. Walton
Optics 2021, 2(3), 169-183; https://0-doi-org.brum.beds.ac.uk/10.3390/opt2030016 - 23 Aug 2021
Cited by 3 | Viewed by 2616
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. Full article
(This article belongs to the Special Issue Feature Papers in Optics)
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14 pages, 8199 KiB  
Article
Study of Superoscillating Functions Application to Overcome the Diffraction Limit with Suppressed Sidelobes
by Svetlana N. Khonina, Ekaterina D. Ponomareva and Muhammad A. Butt
Optics 2021, 2(3), 155-168; https://0-doi-org.brum.beds.ac.uk/10.3390/opt2030015 - 20 Aug 2021
Viewed by 2886
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Feature Papers in Optics)
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21 pages, 9517 KiB  
Article
Refractometric Properties of a TFBG Sensor Demodulated Using α-Shape Modified Delaunay Triangulation
by Luigi Fazzi and Roger M. Groves
Optics 2021, 2(2), 113-133; https://0-doi-org.brum.beds.ac.uk/10.3390/opt2020012 - 09 Jun 2021
Cited by 6 | Viewed by 3200
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Feature Papers in Optics)
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9 pages, 1481 KiB  
Article
Nature of Photoelectric Effect in a Ge-on-Si SPAD at Ultralow Energy in Incident Pulsed Laser Radiation
by Valeri I. Kovalev
Optics 2021, 2(1), 45-53; https://0-doi-org.brum.beds.ac.uk/10.3390/opt2010004 - 31 Jan 2021
Cited by 1 | Viewed by 2201
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Feature Papers in Optics)
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