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Women’s Special Issue Series: Photonics
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Women’s Special Issue Series: Photonics

A special issue of Photonics (ISSN 2304-6732).

Deadline for manuscript submissions: closed (20 October 2023) | Viewed by 62555

Special Issue Editors

Prof. Dr. Frauke Alves

E-Mail Website
Guest Editor
1. Institute of Diagnostic and Interventional Radiology, Clinic of Hematology and Medical Oncology, University Medical Center Goettingen (UMG), 37075 Göttingen, Germany
2. Max-Planck-Institute for Experimental Medicine, 37075 Göttingen, Germany
Interests: multiphoton microscopy; X-ray based imaging; light sheet microscopy; virtual histology, translational imaging; oncology; inflammation; lung disease
Dr. Hongping Zhao

E-Mail Website
Guest Editor
Department of Electrical and Computer Engineering & Department of Materials Science and Engineering, The Ohio State University, Columbus, OH 43210, USA
Interests: synthesis and physics of wide bandgap (WBG) and ultra-wide bandgap (UWBG) semiconductor materials and devices, as well as low-dimensional semiconductor nano-materials and devices. Metalorganic chemical vapor deposition of a wide range of semiconductor materials including III-nitrides, II-IV-nitrides and (Al-, Ga-, In-)2O3, as well as the low pressure chemical vapor deposition of Gallium Oxide (Ga2O3) and Indium Oxide (In2O3)
Dr. Zhaoran (Rena) Huang

E-Mail Website
Guest Editor
Department of Electrical, Computer and Systems Engineering (ECSE), Rensselaer Polytechnic Institute, Troy, NY 12180, USA
Interests: optoelectronic devices; integrated slow wave structures; electro-optic modulators; optical reservoir computing; optical machine learning
Dr. Irina Yanina

E-Mail Website
Guest Editor
Research-Educational Institute of Optics and Biophotonics, Science Medical Center, Saratov National Research State University, Saratov 410012, Russia
Interests: optics of biological tissues; biomedical optics; optical control parameters of biological tissues; the study of transport of drugs in biological tissues; spectroscopy and imaging in biomedicine, physics, optical and laser measurements; optical coherency and multiphoton tomography; fluorescence; nanobiophotonics
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

This Special Issue has been proposed to encourage the participation of women in the enhancement and proliferation of the topical subjects of Photonics, in their respective and specific research fields. In particular, we cordially invite women scientists to contribute comprehensive interdisciplinary research, based on new and innovative perspectives, wherein Photonics can play its relevant key role in scientific dissemination. Original theoretical and experimental research papers, such as surveys in all areas related to Photonics, are welcome. The following are some potential subjects and application areas:

  • Biophotonics, biomedical optics, and medical optics;
  • Semiconductor photonics and optoelectronics;
  • Nanotechnology and nanostructures in optics;
  • Quantum optics, quantum computing, and applications;
  • Photonic materials and technology;
  • Metamaterials, plasmonics, and nanophotonics;
  • Integrated optoelectronics and integrated optics;
  • Photonics device and technologies;
  • Optical communications and systems;
  • Nonlinear and ultrafast optics;
  • Imaging systems and holography;
  • Computational photonics and nanostructures;
  • Photonics for energy and green technologies;
  • Fundamentals and applications of photonics/optics
  • Photon–electron–phonon interaction in nanostructures;
  • Physics and simulation: material properties, device technologies, and integrated systems.

Articles where the lead authors are women, or that are completely authored by women, are encouraged. However, we welcome submissions from all authors irrespective of gender.

Prof. Dr. Frauke Alves
Dr. Hongping Zhao
Dr. Zhaoran (Rena) Huang
Dr. Irina Yanina
Guest Editors

Women’s Special Issue Series

This Special Issue is part of Photonics's Women’s Special Issue Series, hosted by women editors for women researchers. The Series advocates the advancement of women in science. We invite contributions to the Special Issue whose lead authors identify as women. The submission of articles with all-women authorship is especially encouraged. However, we do welcome articles from all authors, irrespective of gender.

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. Photonics is an international peer-reviewed open access monthly 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 2400 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.

Keywords

  • tissue optics
  • multiple scattering
  • quasi-elastic scattering
  • doppler effect
  • absorption
  • index of refraction
  • random phase screen
  • speckles
  • optical coherence tomography (OCT)
  • diffusion wave spectroscopy
  • polarized light
  • optical clearing

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Published Papers (29 papers)

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Research

9 pages, 2376 KiB  
Communication
Scalable Optical Frequency Rulers with the Faraday Effect
by Jyun-Ping Chang, Cheng-Mu Tsai, Panfeng Ding, Jixiong Pu and Pin Han
Photonics 2024, 11(2), 127; https://doi.org/10.3390/photonics11020127 - 29 Jan 2024
Cited by 1 | Viewed by 1266
Abstract
Optical frequency rulers (OFRs) can be used as optical wavelengths or frequency references for spectra modulation or to determine unknown wavelengths. In the past, difficult-to-perform and complicated mechanisms were used to make OFRs, such as double slits with a high-speed fluid or an [...] Read more.
Optical frequency rulers (OFRs) can be used as optical wavelengths or frequency references for spectra modulation or to determine unknown wavelengths. In the past, difficult-to-perform and complicated mechanisms were used to make OFRs, such as double slits with a high-speed fluid or an external circuit to control the liquid crystal birefringence. Since then, a later research study introduced a simple structure for producing OFRs by utilizing the optical activity block and two polarizers. This achieved a movable OFR that was controllable by simply rotating one of the polarizers. However, this mechanical rotation hindered its high-speed applicability. In this article, a more advanced, scalable OFR scheme using the Faraday effect is proposed. It is controlled by varying the magnetic field intensity, which is not a mechanical method, and it can be changed at high speeds. The numerical results demonstrate that those OFR spectral ticks can be scaled to reach a higher or lower tick density, greatly benefiting the wavelength decision jobs. Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Photonics)
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12 pages, 2961 KiB  
Communication
Performance Analysis of a Single Light Source Bidirectional Visible Light Communication Reverse Reflection Link
by Ying Zhang, Jiawei Ren, Kexin Li and Haibo Mou
Photonics 2024, 11(1), 18; https://doi.org/10.3390/photonics11010018 - 26 Dec 2023
Viewed by 1296
Abstract
Visible light communication has the advantages of large bandwidth, high security, and no RF interference, among which LED light sources are an important light source for indoor visible light communication. The use of LED as a light source for visible full-duplex communication is [...] Read more.
Visible light communication has the advantages of large bandwidth, high security, and no RF interference, among which LED light sources are an important light source for indoor visible light communication. The use of LED as a light source for visible full-duplex communication is both to meet the lighting requirements and to ensure high-speed transmission of information. The uplink using the “cat’s eye” reverse modulation system can greatly reduce the system complexity of the reverse reflector. In order to analyze the factors affecting the optical power at the receiving end of the uplink of the indoor single light source visible light communication, this paper establishes the indoor visible light full-duplex communication system model and deduces the calculation method of the effective incidence angle of the uplink transmission light and the movable range of the reverse reflection end according to the model. The results show that when the link distance of the BK7 lens is 3 m, the lens aperture is increased from 100 mm to 150 mm, the lens focal length is increased from 100 mm to 150 mm, the travel distance of the reverse reflector is increased by 60%, and the effective range of the incidence angle is increased by about twice. In the absence of link loss, each 1 m increase in link distance increases the maximum travel distance of the reverse reflector by 0.8 m. Increasing the lens aperture, decreasing the focal length, and increasing the link distance can improve the movable range of the reverse reflector, and the effective incidence angle changes more gently with the position of the reverse reflector. Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Photonics)
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16 pages, 3486 KiB  
Article
NaYF4: Yb,Er Upconversion Nanoparticles for Imaging: Effect on Red Blood Cells
by Anna A. Doronkina, Vyacheslav I. Kochubey, Anastasia V. Maksutova, Alexander B. Pravdin, Artem M. Mylnikov, Nikita A. Navolokin and Irina Yu. Yanina
Photonics 2023, 10(12), 1386; https://doi.org/10.3390/photonics10121386 - 17 Dec 2023
Cited by 2 | Viewed by 2292
Abstract
(1) Background: Upconversion nanoparticles (UCNPs) are a promising tool for biological tissue structure visualization and photodynamic therapy (PDT). The luminescence of such NPs is excited in the spectrum’s near-infrared (NIR) region, while the NPs luminesce in the visible region. Conjugating such NPs with [...] Read more.
(1) Background: Upconversion nanoparticles (UCNPs) are a promising tool for biological tissue structure visualization and photodynamic therapy (PDT). The luminescence of such NPs is excited in the spectrum’s near-infrared (NIR) region, while the NPs luminesce in the visible region. Conjugating such NPs with photodynamic dyes that absorb their luminescence makes it possible to increase the depth at which PDT is performed. (2) Methods: We conducted a comprehensive study on the possibility of using NaYF4:Er:Yb UCNPs in vivo for imaging and PDT. The NPs were synthesized by a hydrothermal method. The synthesis of NPs with a size of 80 nm and hexagonal structure was demonstrated. (3) Results: The accumulation of NPs in organs after their intravenous injection into rats was studied. The effect of NPs on the shape, size, and degree of aggregation of red blood cells (RBC) was also investigated. (4) Conclusions: The possibility of luminescent visualization of NPs in histological sections and their subcutaneous distribution is demonstrated. All investigated particles showed moderate toxicity, causing mostly reversible changes. Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Photonics)
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12 pages, 3580 KiB  
Article
The Growth Mechanism, Luminescence, and Lasing of Polyhedral ZnO Microcrystals with Whispering-Gallery Modes
by Ludmila A. Zadorozhnaya, Andrey P. Tarasov and Vladimir M. Kanevsky
Photonics 2023, 10(12), 1328; https://doi.org/10.3390/photonics10121328 - 29 Nov 2023
Cited by 2 | Viewed by 1395
Abstract
This work studies the features of the formation of isometric polyhedral ZnO microcrystals that provide stimulated emission and whispering-gallery-mode (WGM) lasing in the near-UV range. For this purpose, the growth stages of such crystals in the process of gas-transport synthesis and the luminescent [...] Read more.
This work studies the features of the formation of isometric polyhedral ZnO microcrystals that provide stimulated emission and whispering-gallery-mode (WGM) lasing in the near-UV range. For this purpose, the growth stages of such crystals in the process of gas-transport synthesis and the luminescent properties of the structures obtained at each stage were investigated. It was shown that the growth of laser microcrystals begins with the formation of microspheroids with thin ZnO shells. Such spheroids exhibit mainly white luminescence with a small contribution of near-UV emission. Increasing the synthesis duration results in thickening and faceting of the spheroid shells, as well as a decrease in the contribution of the yellow–red component to the luminescence spectrum. At the same time, ZnO microcrystallites nucleate and grow inside the spheroids, using as a material the remains of a liquid zinc drop and oxygen entering the spheroids through their shells. Such growth conditions allow them to take on an equilibrium polyhedral shape. Eventually, upon destruction of the spheroid shell, a polyhedral ZnO microcrystal supporting WGMs is observed. Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Photonics)
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15 pages, 1037 KiB  
Article
Bound States in the Continuum and Induced Resonances in a Simple Plasmonic Waveguide with Sensing Application
by Yamina Rezzouk, Soufyane Khattou, Madiha Amrani, Adnane Noual, El Houssaine El Boudouti, Abdelkrim Talbi and Bahram Djafari-Rouhani
Photonics 2023, 10(11), 1284; https://doi.org/10.3390/photonics10111284 - 20 Nov 2023
Cited by 4 | Viewed by 2147
Abstract
A Friedrich–Wintgen bound state in the continuum (FW-BIC) is of particular interest in the field of wave physics phenomena. It is induced via the destructive interference of two modes that belong to the same cavity. In this work, we analytically and numerically show [...] Read more.
A Friedrich–Wintgen bound state in the continuum (FW-BIC) is of particular interest in the field of wave physics phenomena. It is induced via the destructive interference of two modes that belong to the same cavity. In this work, we analytically and numerically show the existence of FW-BIC in a T-shaped cavity composed of a stub of length d0 and two lateral branches of lengths d1 and d2, attached to an infinite waveguide. The whole system consists of metal–insulator–metal (MIM) plasmonic waveguides that operate in the telecommunication range. Theoretically, when d1 and d2 are commensurated, BIC is induced by these two branches. This latter is independent of d0 and the infinite waveguide, where the T structure is grafted. By breaking the BIC condition, we obtain a plasmon-induced transparency (PIT) resonance. The PIT resonance’s sensitivity to the dielectric material of the waveguide may be exploited to design a sensitive nanosensor suitable for sensing platforms, thanks to its very small footprint. A sensitivity of 1400 nm/RIU and a resolution of 1.86×10−2 RIU showed a high level of performance that the designed structure achieved. Moreover, this structure could also be used as a biosensor, in which we have studied the detection of the concentration in the human body, such as Na+, K+, and glucose solutions, and these sensitivities can reach 0.21, 0.28, and 1.74 nm dL/mg, respectively. Our designed structure advances with technology and has good application prospects, working as a biosensor to detect the blood’s hemoglobin level. The analytical results, obtained via Green’s function method, are validated via numerical simulations using Comsol Multiphysics software based on the finite element method. Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Photonics)
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11 pages, 1828 KiB  
Communication
A Symmetric Parity–Time Coupled Optoelectronic Oscillator Using a Polarization–Dependent Spatial Structure
by Fengling Zhang, Xiaodong Lin, Zhengmao Wu and Guangqiong Xia
Photonics 2023, 10(11), 1236; https://doi.org/10.3390/photonics10111236 - 6 Nov 2023
Cited by 2 | Viewed by 1664
Abstract
We propose and experimentally investigate a symmetric parity-time (PT) coupled optoelectronic oscillator (COEO) based on a polarization-dependent spatial structure. In such a COEO system, the gain/loss and coupling coefficients of two orthogonal polarization optical waves can be controlled by adjusting the polarization controller [...] Read more.
We propose and experimentally investigate a symmetric parity-time (PT) coupled optoelectronic oscillator (COEO) based on a polarization-dependent spatial structure. In such a COEO system, the gain/loss and coupling coefficients of two orthogonal polarization optical waves can be controlled by adjusting the polarization controller (PC) and the bias voltage of a Mach-Zehnder modulator (MZM). The single-mode selection of a microwave signal can be implemented by the PT symmetry breaking of a special mode. The performance of the proposed COEO is experimentally examined, and a 10.0 GHz microwave signal with a phase noise of −109.1 dBc/Hz @ 10 kHz and a side mode suppression ratio of 51.4 dB is generated. Moreover, an optical frequency comb with a comb tooth spacing of 10.0 GHz and a bandwidth of 100 GHz within a 10 dB amplitude variation can be simultaneously generated. Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Photonics)
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11 pages, 2760 KiB  
Article
Theoretical Study of Multicascade Raman Microlasers Based on TeO2–WO3–Bi2O3 Glass
by Elena A. Anashkina, Maria P. Marisova and Alexey V. Andrianov
Photonics 2023, 10(10), 1137; https://doi.org/10.3390/photonics10101137 - 11 Oct 2023
Cited by 1 | Viewed by 1051
Abstract
The development and investigation of miniature narrow-line coherent light sources based on microresonators with low-power-consumption whispering gallery modes (WGMs) is an actual trend in modern photonics. Raman WGM microlasers can operate at wavelengths inaccessible to traditional laser media and provide a huge pump [...] Read more.
The development and investigation of miniature narrow-line coherent light sources based on microresonators with low-power-consumption whispering gallery modes (WGMs) is an actual trend in modern photonics. Raman WGM microlasers can operate at wavelengths inaccessible to traditional laser media and provide a huge pump frequency tuning range. Here, we propose and theoretically study multicascade Raman microlasers based on soft tellurite TeO2–WO3–Bi2O3 glass WGM microresonators (microspheres) which can operate in the near-IR and mid-IR with the pump in the telecommunication range. Thanks to a large Raman gain (120 times exceeding the maximum Raman gain of silica glass) and a huge Raman frequency shift of 27.5 THz for this glass, the Raman waves at 1.83 µm, 2.21 µm, 2.77 µm, and 3.7 µm in the first, second, third, and fourth cascades, respectively, are theoretically demonstrated with a pump at 1.57 µm. We analyze in detail the influence of different factors on the characteristics of the generated Raman waves, such as microsphere diameters, Q-factors, pump powers, and detuning of the pump frequency from exact resonance. We also solve a thermo-optical problem to show that the temperature of a soft glass microresonator heated due to partial thermalization of pump power remains below the glass transition temperature. To the best of our knowledge, mid-IR tellurite glass Raman WGM microlasers have not been studied before. Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Photonics)
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14 pages, 4052 KiB  
Article
ZnO-Based Materials: From Pauli’s Nonsense to a Key Enabling Technology
by Juan Francisco Ramos-Justicia, Adalyz Ferreiro, Gregorio Flores-Carrasco, Sara Rodríguez-Cañamero, Ana Urbieta, María Eugenia Rabanal and Paloma Fernández
Photonics 2023, 10(10), 1106; https://doi.org/10.3390/photonics10101106 - 30 Sep 2023
Viewed by 1558
Abstract
In this work, we aim to highlight the increasing interest in semiconductors, particularly ZnO. A revision of the evolution of the scientific production on three selected topics has been conducted. As an indicator of scientific production, the number of publications indexed in the [...] Read more.
In this work, we aim to highlight the increasing interest in semiconductors, particularly ZnO. A revision of the evolution of the scientific production on three selected topics has been conducted. As an indicator of scientific production, the number of publications indexed in the Web of Science Data Base has been used. The search terms selected range from the general to the particular: semiconductors, oxide semiconductors, and ZnO. The period considered is from 1 January 1900 to 6 June 2023. The importance of doping processes in tailoring the properties of these materials, and the relevance of the most recently derived applications are also revised. Since many of the most recent applications that have been developed or are under development refer to optoelecronic properties, doping with rare earth elements has a central role. This was the reason behind choosing the system ZnO doped with Rare Earth elements (Eu, Gd, and Ce) and codoped with Ru to illustrate the materials’ tuning potential of doping processes. Morphology, crystal structure, and luminescent properties have been investigated. Upon doping, both the Near Band Edge and the Deep Level emissions show a remarkable difference due to the change in the relative weight of the components constituting these bands. The spectra in all cases extend over the whole visible range, with a main emission in the violet-blue region corresponding to the Near Band Edge, and a broad band extending from the blue-green to orange-red region associated with the presence of different defects. Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Photonics)
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13 pages, 2663 KiB  
Article
Manganese-Doped Carbon Dots as a Promising Nanoprobe for Luminescent and Magnetic Resonance Imaging
by Evgeniia A. Stepanidenko, Anna A. Vedernikova, Zilya F. Badrieva, Ekaterina A. Brui, Saikho O. Ondar, Mikhail D. Miruschenko, Olga V. Volina, Aleksandra V. Koroleva, Evgeniy V. Zhizhin and Elena V. Ushakova
Photonics 2023, 10(7), 757; https://doi.org/10.3390/photonics10070757 - 30 Jun 2023
Cited by 6 | Viewed by 2364
Abstract
Luminescent carbon nanodots (CDs) are a low-toxic nanomaterial with a tunable emission in a wide spectral range and with various functional groups on the surface. Therefore, CDs can prospectively serve as luminescent nanoprobes for biomedical applications, such as drug-delivery, visualization, sensing, etc. The [...] Read more.
Luminescent carbon nanodots (CDs) are a low-toxic nanomaterial with a tunable emission in a wide spectral range and with various functional groups on the surface. Therefore, CDs can prospectively serve as luminescent nanoprobes for biomedical applications, such as drug-delivery, visualization, sensing, etc. The doping of CDs with paramagnetic or transition metals allows the expansion of the range of applications of CDs and the fabrication of a multimodal nanoprobe for bioimaging. Here, we developed CDs doped with manganese (Mn) based on commonly used precursors—o-phenylenediamine or citric acid and formamide. The chemical structure, morphology, optical properties, and magnetic resonance responses have been carefully studied. The obtained CDs are up to 10 nm, with emissions observed in the 400–650 nm spectral region. CDs exhibit an ability to reduce both T1 and T2 relaxation times by up to 6.4% and 42.3%, respectively. The high relaxivity values suggest the use of CDs as promising dual-mode contrast agents for T1 and T2 MRI. Therefore, our developed CDs can be utilized as a new multifunctional nanoscale probe for photoluminescent and magnetic resonance bioimaging. Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Photonics)
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11 pages, 934 KiB  
Article
Highly Luminescent Rb-Doped Cs4PbBr6 Nanocrystals in Borogermanate Glass
by Damir Valiev, Rufina Kharisova, Anastasiia Babkina, Ksenia Zyryanova, Natalia Kuzmenko, Yevgeniy Sgibnev, Artem Shelaev and Alexander V. Baryshev
Photonics 2023, 10(7), 729; https://doi.org/10.3390/photonics10070729 - 26 Jun 2023
Cited by 3 | Viewed by 1687
Abstract
For the first time, the synthesis, luminescent and structural properties of stable perovskite-type (Cs1−xRbx)4PbBr6 (R = Cs, Rb) nanocrystals are shown. In the absence of rubidium, Cs4PbBr6 and CsPbBr3 perovskite crystals precipitate [...] Read more.
For the first time, the synthesis, luminescent and structural properties of stable perovskite-type (Cs1−xRbx)4PbBr6 (R = Cs, Rb) nanocrystals are shown. In the absence of rubidium, Cs4PbBr6 and CsPbBr3 perovskite crystals precipitate in the ZnO–Na2O–B2O3–GeO2 glass matrix. With ascending rubidium content, the precipitation of (Cs,Rb)4PbBr6 nanocrystals is replaced by the Rb4PbBr6 nanocrystals nucleation. Nucleated nanocrystals exhibit an intense green luminescence. With an increase of the rubidium content, the luminescence maximum shifts to the blue region, the luminescence quantum yield increases from 28 to 51%, and the average decay time increases from 2 to 8 ns. Several assumptions have been made about the nature of the green luminescence of perovskite-like Cs4PbBr6 and (Cs,Rb)4PbBr6 crystals in glasses. It is concluded that the most probable cause is the impurity inclusions of CsPbBr3 and (Cs,Rb)PbBr3 crystals. Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Photonics)
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15 pages, 5696 KiB  
Article
Turn a Shrimp into a Firefly: Monitoring Tissue pH in Small Crustaceans Using an Injectable Hydrogel Sensor with Infrared Excitation and Visible Luminescence
by Anna Nazarova, Anton Gurkov, Yaroslav Rzhechitskiy, Ekaterina Shchapova, Andrei Mutin, Alexandra Saranchina, Anastasiia Diagileva, Nadezhda Bolbat, Pavel Krivoshapkin and Maxim Timofeyev
Photonics 2023, 10(6), 697; https://doi.org/10.3390/photonics10060697 - 20 Jun 2023
Cited by 1 | Viewed by 2697
Abstract
Various implantable optical sensors are an emerging tool in animal physiology and medicine that may provide real-time information about body fluids without tissue extraction. Such sensors are often fluorescence-based and require strong visible external illumination during signal acquisition, which causes anxiety or even [...] Read more.
Various implantable optical sensors are an emerging tool in animal physiology and medicine that may provide real-time information about body fluids without tissue extraction. Such sensors are often fluorescence-based and require strong visible external illumination during signal acquisition, which causes anxiety or even stress for small animals and thus may influence the physiological parameters being measured. In order to overcome this obstacle, here, we combined a fluorescent molecular pH probe with upconverting particles within a hydrogel fiber suitable for injection into small crustaceans. The green luminescence of the particles under non-visible infrared illumination excited fluorescence of the molecular probe and allowed for pH measurements after correction of the probe readout for luminescence intensity. The developed optical setup based on a common microscope ensured effective visualization of the sensor and spectral pH measurements through the translucent exoskeleton of the amphipod (Amphipoda, Crustacea) Eulimnogammarus verrucosus, endemic to ancient Lake Baikal. Testing the sensors in these cold-loving crustaceans under environmentally relevant temperature increases showed alkalization of amphipod internal media by 0.2 soon after the start of the experiment, while further increases led to acidification by 0.5. The applied approach for simple sensor preparation can be useful in building other implantable optical sensors for light-sensitive organisms. Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Photonics)
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17 pages, 5849 KiB  
Article
Numerical and Experimental Investigation of Slope Deformation under Stepped Excavation Equipped with Fiber Optic Sensors
by Jia Wang, Wenwen Dong, Wenzhao Yu, Chengcheng Zhang and Honghu Zhu
Photonics 2023, 10(6), 692; https://doi.org/10.3390/photonics10060692 - 17 Jun 2023
Cited by 2 | Viewed by 1660
Abstract
The real-time evaluation of slope stability is a crucial technical issue in foundation excavation and slope construction. However, conventional monitoring methods often fall short of achieving real-time and accurate measurements, which poses challenges to the timely assessment of slope stability. To address this [...] Read more.
The real-time evaluation of slope stability is a crucial technical issue in foundation excavation and slope construction. However, conventional monitoring methods often fall short of achieving real-time and accurate measurements, which poses challenges to the timely assessment of slope stability. To address this problem, laboratory tests and numerical simulations were jointly used to evaluate slope stability in this paper. In numerical simulations, the finite element method (FEM) results clearly illustrate the distribution and evolution of internal strain during slope excavation, and the limit equilibrium method (LEM) calculates changes in the safety factor. In laboratory tests, the fiber Bragg grating (FBG) sensing technology was employed to monitor the internal strain of the slope in real time. The distribution characteristics of the slope internal strain field under the condition of stepped excavation were analyzed, and the feasibility of strain-based evaluation of slope stability was discussed. The measurements with FBG sensing technology agree well with the numerical simulation results, indicating that FBG can effectively monitor soil strain information. Of great significance is that the maximum horizontal strain of the slope is closely related to the safety factor and can be used to evaluate slope stability. Notably, the horizontal soil strain of the slope provides insight into both the formation and evolution of the critical sliding surface during excavation. The combination of numerical simulation and intelligent monitoring technology based on FBG proposed in this paper provides a reference for capturing strain information inside the slope and realizing real-time assessment and critical warning of slope stability. Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Photonics)
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23 pages, 6295 KiB  
Article
Design, Fabrication and Validation of Mixed Order Distributed Feed-Back Organic Diode Laser Cavity
by Amani Ouirimi, Alex Chamberlain Chime, Nixson Loganathan, Mahmoud Chakaroun, Daan Lenstra and Alexis P. A. Fischer
Photonics 2023, 10(6), 670; https://doi.org/10.3390/photonics10060670 - 8 Jun 2023
Cited by 1 | Viewed by 1638
Abstract
In the context of the quest for the organic laser diode, we address a key challenge to design and fabricate high-quality factor cavities compatible with electrical excitation of organic semiconductors. More precisely, we present the design of DFB micro-cavities for integration in organic [...] Read more.
In the context of the quest for the organic laser diode, we address a key challenge to design and fabricate high-quality factor cavities compatible with electrical excitation of organic semiconductors. More precisely, we present the design of DFB micro-cavities for integration in organic laser diodes and their validation under optical pumping. To design high-quality factor mixed-order DFB micro-cavities, we consider the half- and quarter-wavelength multilayered system and use the optical waveguide analysis to quantify the effective indices of the high and low indices, and the matrix transfer method to calculate the reflectances. Matrices of DFB micro-cavities made from different doses and different grating periods were fabricated. We then identified those showing laser emission under optical pumping as an indication of optimal matching of their resonance wavelength with respect to the electroluminescence peak of the organic gain material. Potential applications of organic laser diodes deal with light communication, spectroscopy, sensors, and other applications where heterogenous integration is important. Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Photonics)
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13 pages, 8199 KiB  
Communication
Modification of the Emission Spectrum of a Quantum Emitter in the Vicinity of Bismuth Chalcogenide Microparticles
by Margarita-Georgia Papadaki, Nikolaos Kyvelos, Emmanuel Paspalakis and Vassilios Yannopapas
Photonics 2023, 10(6), 658; https://doi.org/10.3390/photonics10060658 - 7 Jun 2023
Cited by 1 | Viewed by 1532
Abstract
We examine theoretically the effect of bismuth chalcogenide microparticles on the spontaneous emission of a double-V-type quantum emitter in free space. We have found, in particular, that the presence of a single microparticle causes a high degree of quantum interference in the way [...] Read more.
We examine theoretically the effect of bismuth chalcogenide microparticles on the spontaneous emission of a double-V-type quantum emitter in free space. We have found, in particular, that the presence of a single microparticle causes a high degree of quantum interference in the way the quantum emitter releases energy in the process of spontaneous emission. This, in turn, leads to significant changes in the spectrum of the emitted energy. The quantum emitter’s initial state is crucial to how the energy is released in the presence of the microparticle. This observation has potential implications for quantum computing, particularly for reading the state of atomic qubits. When two microparticles are present, the effect is more pronounced, particularly when the quantum emitter is located in the gap between the particles. Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Photonics)
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14 pages, 6390 KiB  
Communication
Advances of the Cubic Symmetry Crystalline Systems to Create Complex, Bright Luminescent Ceramics
by Valentina Smyslova, Daria Kuznetsova, Alexey Bondaray, Petr Karpyuk, Mikhail Korzhik, Ilya Komendo, Vladimir Pustovarov, Vasilii Retivov and Dmitry Tavrunov
Photonics 2023, 10(5), 603; https://doi.org/10.3390/photonics10050603 - 22 May 2023
Cited by 5 | Viewed by 1736
Abstract
A method to create compositionally disordered compounds with a high number of cations in the matrices, that utilize the cubic spatial symmetry of the garnet-type crystalline systems is demonstrated. Mixtures of the garnet-type powdered materials solely doped with Ce were used to create [...] Read more.
A method to create compositionally disordered compounds with a high number of cations in the matrices, that utilize the cubic spatial symmetry of the garnet-type crystalline systems is demonstrated. Mixtures of the garnet-type powdered materials solely doped with Ce were used to create atomic compositions of high complexity. Several mixed systems, namely Gd3Al2Ga3O12/(Gd,Y)3Al2Ga3O12, Y3Al5O12/Gd3Al2Ga3O12, and Y3Al5O12/Y3Al2Ga3O12 were annealed, compacted and sintered in air. The materials were evaluated for structural, luminescence, and scintillation properties. It was demonstrated that the properties of the resulting ceramics are a little dependent on the granularity of powders when the median particle size is below ~5 μm. Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Photonics)
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16 pages, 4243 KiB  
Article
Numerical Simulation of a Light Field Structure in an Integrating Sphere via the Monte Carlo Method
by Anna Yushmanova, Sergey Sheberstov, Dmitry Glukhovets and Sergey Pogosyan
Photonics 2023, 10(5), 593; https://doi.org/10.3390/photonics10050593 - 19 May 2023
Cited by 4 | Viewed by 1650
Abstract
The integrated cavity absorption meter is designed to measure the seawater absorption coefficient spectra which are necessary for studying ocean productivity and heat balance. The performed numerical simulations of a light field structure made it possible to improve the measurement technique. Its results [...] Read more.
The integrated cavity absorption meter is designed to measure the seawater absorption coefficient spectra which are necessary for studying ocean productivity and heat balance. The performed numerical simulations of a light field structure made it possible to improve the measurement technique. Its results showed that the use of the Lambertian model allows to reduce the calculation time by two orders of magnitude with an acceptable loss of accuracy for these calculations. It is shown that in the case of an integrating sphere made of fluorilon, the use of different volume scattering functions does not affect the calculation result, which is not true in the case of using a sphere with a mirror coating. The effect of an air layer between quartz and fluorilon is considered, and the applicability of the diffusion approximation is verified. Examples of field measurements of the seawater absorption coefficient and its components performed in different water areas of the World Ocean in 2020–2022 are presented. Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Photonics)
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9 pages, 2947 KiB  
Communication
Dimensional Analysis of Double-Track Microstructures in a Lithium Niobate Crystal Induced by Ultrashort Laser Pulses
by Yulia Gulina, Jiaqi Zhu, Alexey Gorevoy, Mikhail Kosobokov, Anton Turygin, Boris Lisjikh, Andrey Akhmatkhanov, Vladimir Shur and Sergey Kudryashov
Photonics 2023, 10(5), 582; https://doi.org/10.3390/photonics10050582 - 17 May 2023
Cited by 1 | Viewed by 2277
Abstract
Double-track microstructures were induced in the bulk of a z-cut lithium niobate crystal by 1030 nm 240 fs ultrashort laser pulses with a repetition rate of 100 kHz at variable pulse energies exceeding the critical Kerr self-focusing power. The microstructure topography was characterized [...] Read more.
Double-track microstructures were induced in the bulk of a z-cut lithium niobate crystal by 1030 nm 240 fs ultrashort laser pulses with a repetition rate of 100 kHz at variable pulse energies exceeding the critical Kerr self-focusing power. The microstructure topography was characterized by atomic force microscopy in piezoelectric response mode. The spatial positions of laser-induced modification regions inside lithium niobate in the case of laser beam propagation along the crystal optical axis can be directly predicted by simple analytical expressions under the paraxial approximation. A dimensional analysis of the morphology of the double-track structures revealed that both their length and width exhibit a monotonous increase with the pulse energy. The presented results have important implications for direct laser writing technology in crystalline dielectric birefringent materials, paving the way to control the high spatial resolution by means of effective energy deposition in modified regions. Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Photonics)
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14 pages, 2789 KiB  
Article
Quantitative Detection of Microplastics in Water through Fluorescence Signal Analysis
by Roberto Pizzoferrato, Yuliu Li and Eleonora Nicolai
Photonics 2023, 10(5), 508; https://doi.org/10.3390/photonics10050508 - 27 Apr 2023
Cited by 7 | Viewed by 4084
Abstract
Microplastics (MPs) have recently been acknowledged as a new major and ubiquitous environmental pollutant with still unclear, yet potentially high, risks for different ecosystems and human health. Nevertheless, quantitative identification protocols rely on long and subjective visual counting necessarily performed on microscopes by [...] Read more.
Microplastics (MPs) have recently been acknowledged as a new major and ubiquitous environmental pollutant with still unclear, yet potentially high, risks for different ecosystems and human health. Nevertheless, quantitative identification protocols rely on long and subjective visual counting necessarily performed on microscopes by well-trained operators. In this study, an automatic, fast, portable, and inexpensive method for the quantitative detection of MPs in water is proposed. The system is based on the typical optical setup of a fluorescence confocal microscope specifically adapted to automatically count dye-stained MPs in flowing liquids using a low-power laser beam. The fluorescence pulses emitted by flowing MPs are revealed and processed by a specific software using a pattern recognition algorithm to discriminate and count real fluorescence pulses out of noise fluctuations. The system was calibrated with commercial orange fluorescent 10 µm and 1 µm polystyrene microspheres, and remarkable agreement with theoretical predictions was obtained regarding different parameters. Tests were also performed with laboratory-prepared MPs dispersed in different types of real water samples. In this case, the agreement with theory was slightly worse and differences found in the quantitative results require further investigation. However, the present study demonstrated the proof of concept of a method for quick automated MP counting in water. Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Photonics)
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10 pages, 12425 KiB  
Communication
GaAs Linear Polarizer with a High Extinction Ratio for Extended Short-Wave Infrared Detection
by Leidong Shi, Lidan Lu, Guang Chen, Yulin Feng, Yanlin He, Guanghui Ren, Jianzhen Ou and Lianqing Zhu
Photonics 2023, 10(5), 489; https://doi.org/10.3390/photonics10050489 - 24 Apr 2023
Cited by 2 | Viewed by 2377
Abstract
Metasurfaces have shown an unprecedented ability to modulate electromagnetic waves at subwavelength scales, especially polarized optical metasurfaces, applied for imaging, navigation and detection. In this work, a kind of efficient all-dielectric diatomic metasurface for polarization and phase changing, consisting of a pair of [...] Read more.
Metasurfaces have shown an unprecedented ability to modulate electromagnetic waves at subwavelength scales, especially polarized optical metasurfaces, applied for imaging, navigation and detection. In this work, a kind of efficient all-dielectric diatomic metasurface for polarization and phase changing, consisting of a pair of GaAs nanopillar and nanocube, is proposed. By adjusting the unit cell structural parameters, the polarization state can be controlled and adjusted at the short-wave infrared (SWIR) band (1~3 μm). At the wavelength of 2125 nm, the maximum transmission efficiency, the extinction ratio and the linear polarization degree can reach 93.76%, 40.99 dB and 0.99, respectively. Overall, this all-dielectric diatomic metasurface has broad application potential in extended SWIR polarization detection. Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Photonics)
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10 pages, 1604 KiB  
Article
Classification of Healthy and Cancer Colon Cells Grown on Glass Coverslip by Means of Fourier Transform Infrared Spectroscopy and Multivariate Methods
by Giuseppe Perna, Vito Capozzi and Maria Lasalvia
Photonics 2023, 10(4), 481; https://doi.org/10.3390/photonics10040481 - 21 Apr 2023
Cited by 4 | Viewed by 1865
Abstract
For several years, Fourier transform infrared (FTIR) microspectroscopy has been proving to be very promising for use in cytological diagnostics because of its capability of providing rapid and label-free biochemical information about cell samples. The adoption of FTIR as a clinical tool has [...] Read more.
For several years, Fourier transform infrared (FTIR) microspectroscopy has been proving to be very promising for use in cytological diagnostics because of its capability of providing rapid and label-free biochemical information about cell samples. The adoption of FTIR as a clinical tool has been slowed because of the poor compatibility with cells deposited on glass slides, commonly used in clinical practice, because of the absorption of IR radiation by glassy materials in the 1000–1800 cm−1 spectral range. However, the possibility of also obtaining diagnostic information from the IR absorption spectra in the 2700–3700 cm−1 range (including few peaks related to vibrational modes in cell lipids and proteins) has recently emerged. In this work, we investigate the use of the FTIR technique in the 2700–3700 cm−1 range for diagnostic purposes about human colon cells grown on glass coverslips. In fact, using the principal components analysis (PCA) technique, we are able to discriminate FTIR spectra of healthy cells from those of cancerous ones, mainly due to the larger relative lipid content in the former compared to the latter. In addition, principal component analysis-linear discriminate analysis (PCA-LDA) and partial least square-discriminant analysis (PLS-DA) were used to build classification models for unknown FTIR spectra with optimal accuracy. These results support the promotion of the translation of the FTIR technique as a complementary diagnostic tool in cytological routine practice. Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Photonics)
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11 pages, 11235 KiB  
Article
Spectra of a Bragg Microresonator Filled with a Graphene-Containing Medium
by Irina V. Fedorova, Svetlana V. Eliseeva and Dmitrij I. Sementsov
Photonics 2023, 10(4), 449; https://doi.org/10.3390/photonics10040449 - 13 Apr 2023
Viewed by 1265
Abstract
Transmission spectra of a symmetric microresonator structure, with dielectric Bragg mirrors, are obtained. The working cavity of the structure is partially filled by a layer of a quarter-wave thickness of finely layered “graphene–semiconductor” medium, with material parameters controlled by external electric and magnetic [...] Read more.
Transmission spectra of a symmetric microresonator structure, with dielectric Bragg mirrors, are obtained. The working cavity of the structure is partially filled by a layer of a quarter-wave thickness of finely layered “graphene–semiconductor” medium, with material parameters controlled by external electric and magnetic fields. It is shown, that the transformation of the spectra is achieved both by changing the energy state of the graphene layers and by changing the external magnetic field. The spectral characteristics for the inverted and doped states of graphene layers are established. Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Photonics)
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7 pages, 607 KiB  
Communication
Directivity Control of Terahertz Radiation from Single-Color Filament Plasma with Polypropylene Pipe
by Daria Mokrousova, Leonid Seleznev, Dmitrii Pushkarev, Georgy Rizaev, Maximilian Levus, Andrey Koribut and Yakov Grudtsyn
Photonics 2023, 10(4), 443; https://doi.org/10.3390/photonics10040443 - 13 Apr 2023
Viewed by 1425
Abstract
Two-dimensional angular distribution of terahertz emission from single-color filamentation of laser pulses is experimentally studied. The use of a polypropylene pipe makes it possible to transform the angular pattern of terahertz radiation from the original hollow-cone one to a more preferable unimodal structure [...] Read more.
Two-dimensional angular distribution of terahertz emission from single-color filamentation of laser pulses is experimentally studied. The use of a polypropylene pipe makes it possible to transform the angular pattern of terahertz radiation from the original hollow-cone one to a more preferable unimodal structure within the terahertz frequency range. It has been shown that propagation in a dielectric pipe can significantly (up to several orders of magnitude) increase the terahertz radiation amplitude at a required distance. We have also experimentally demonstrated that bending the pipe allows us to control the direction of the terahertz radiation propagation. Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Photonics)
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10 pages, 3999 KiB  
Communication
Study on Temperature and Water Turbulence Impact on Saline Water-Based Wireless Optical Communication
by Shofuro Afifah, Amirullah Wijayanto, Ya-Ling Liu, Shien-Kuei Liaw, Pei-Jun Lee, Chien-Hung Yeh and Ochi Hiroshi
Photonics 2023, 10(4), 383; https://doi.org/10.3390/photonics10040383 - 30 Mar 2023
Cited by 3 | Viewed by 2388
Abstract
Underwater wireless optical communication (UWOC) is a promising solution for Gb/s rate and long-distance underwater communication. However, random changes in the local temperature and salinity of seawater have caused different refractive indices of ocean water. This study investigated the UWOC system in different [...] Read more.
Underwater wireless optical communication (UWOC) is a promising solution for Gb/s rate and long-distance underwater communication. However, random changes in the local temperature and salinity of seawater have caused different refractive indices of ocean water. This study investigated the UWOC system in different saline water while simultaneously changing the temperature and water flow. A maximum bit error rate (BER) of 4.851 × 10−6 was measured at −7.41 dBm in 3 m of 45.56 g/L saline water. By changing the temperature to 30 °C, the bit error rate (BER) value reached 5.12 × 10−6 in the saline water. On the other hand, water flow was generated in various types of water salinity to compare simultaneous environmental effects in the UWOC system. In 45.56 g/L of saline water with water flow, the UWOC system was still capable of reaching a BER value of 4 × 10−4. Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Photonics)
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10 pages, 3349 KiB  
Communication
Movable Optical Frequency Ruler with Optical Activity
by Cheng-Mu Tsai, Jun-Hong Weng, Kuo-Wei Lin and Pin Han
Photonics 2023, 10(2), 206; https://doi.org/10.3390/photonics10020206 - 14 Feb 2023
Cited by 1 | Viewed by 1485
Abstract
Optical frequency rulers (OFR) are suggested for use as optical wavelength or frequency references for spectra manipulation or unknown wavelength measurement. In the past, complicated mechanisms that are not easy to utilize were used to make OFR, such as a double-slits with a [...] Read more.
Optical frequency rulers (OFR) are suggested for use as optical wavelength or frequency references for spectra manipulation or unknown wavelength measurement. In the past, complicated mechanisms that are not easy to utilize were used to make OFR, such as a double-slits with a high-speed fluid or an external circuit to control the liquid crystal birefringence. This work introduces a simple structure to produce an OFR, which should be easier to implement. It utilizes quartz block optical activity and two polarizers. Because of the strong wavelength dependence of the rotatory power, each wavelength component in the spectrum experiences a different amount of polarization angle rotation. Some components whose angles are perpendicular to that of the analyzer are filtered out and naturally form the OFR’s ticks. The numerical results show that those spectral ticks can be moved to higher or lower wavelengths by rotating the analyzer’s angle. This scheme provides another possibility for creating movable OFR with the merit of easy usage. Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Photonics)
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12 pages, 3887 KiB  
Article
Comprehensive Analysis of Copper Plasma: A Laser-Induced Breakdown Spectroscopic Approach
by Asokan Ajith, Mohanachandran Nair Sindhu Swapna, Humberto Cabrera and Sankaranarayana Iyer Sankararaman
Photonics 2023, 10(2), 199; https://doi.org/10.3390/photonics10020199 - 12 Feb 2023
Cited by 5 | Viewed by 3866
Abstract
The emergence of diversified applications of laser-induced breakdown spectroscopy in the biomedical field, electronics, space physics, and material processing necessitates a comprehensive understanding of plasma parameters. The present work delineates the structure and evolution of copper plasma under different ambient pressures (0.01 mbar [...] Read more.
The emergence of diversified applications of laser-induced breakdown spectroscopy in the biomedical field, electronics, space physics, and material processing necessitates a comprehensive understanding of plasma parameters. The present work delineates the structure and evolution of copper plasma under different ambient pressures (0.01 mbar to 100 mbar) along with other plasma parameters. The study reveals the role of ambient pressure in the increase of plasma temperature (Te), electron density (Ne), number of particles in the Debye sphere, plasma frequency, inverse bremsstrahlung absorption coefficient, electron thermal velocity, electron–ion collision frequency and in the decrease of Debye length (λD) and plasma skin depth (PSD). The experimental techniques and the theoretical explanations for the variation of plasma parameters and their applications are also detailed. As the ambient pressure increases, the motion of plasma species becomes restricted, resulting in the increase of Te, calculated using the Boltzmann plot. From the values of λD, PSD, and Ne, it is understood that the copper plasma under investigation is thermally non-relativistic and satisfies McWhirter’s criterion, thus, revealing the local thermodynamic equilibrium condition of plasma. The effects of Debye shielding and stark broadening on the spectral lines are also investigated. Thus, the study helps bring newfangled dimensions to the application of plasma by exploring the possibility of tailoring plasma parameters. Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Photonics)
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13 pages, 9454 KiB  
Article
Interactions of Atomistic Nitrogen Optical Centers during Bulk Femtosecond Laser Micromarking of Natural Diamond
by Elena Rimskaya, Galina Kriulina, Evgeny Kuzmin, Sergey Kudryashov, Pavel Danilov, Alexey Kirichenko, Nikolay Rodionov, Roman Khmelnitskii and Jiajun Chen
Photonics 2023, 10(2), 135; https://doi.org/10.3390/photonics10020135 - 29 Jan 2023
Cited by 4 | Viewed by 1961
Abstract
Micromarks were formed in bulk natural IaAB-type diamond laser-inscribed by 515 nm 0.3 ps femtosecond laser pulses focused by a 0.25 NA micro-objective at variable pulse energies in sub-picosecond visible-range laser regimes. These micromarks were characterized at room temperature (25 °C) by stationary [...] Read more.
Micromarks were formed in bulk natural IaAB-type diamond laser-inscribed by 515 nm 0.3 ps femtosecond laser pulses focused by a 0.25 NA micro-objective at variable pulse energies in sub-picosecond visible-range laser regimes. These micromarks were characterized at room temperature (25 °C) by stationary 3D confocal photoluminescence (PL) microspectroscopy at 405 nm and 532 nm excitation wavelengths. The acquired PL spectra exhibit the increasing pulse-energy-dependent yield in the range of 550–750 nm (NV0, NV− centers) at the expense of the simultaneous reciprocal reduction in the blue–green (490–570 nm, H-band centers) PL yield. The detailed analysis indicates low-energy intensity rise for H-band centers as an intermediate product of vacancy-mediated dissociation of B1 and B2 centers, with H4 centers converting to H3 and NV centers at higher pulse energies, while the laser exposure effect demonstrates the same trend. These results will help solve the problem of direct laser writing technology, which is associated with the writing of micromarks in bulk natural diamond, and promising three-dimensional micro-electrooptical and photonic devices in physics and electronics. Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Photonics)
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13 pages, 4499 KiB  
Article
On the Possibility of Intense Unipolar THz Pulses Formation in Nonhomogeneous Nonequilibrium Nitrogen Plasma Channels
by Anna V. Bogatskaya, Ekaterina A. Volkova and Alexander M. Popov
Photonics 2023, 10(2), 113; https://doi.org/10.3390/photonics10020113 - 21 Jan 2023
Cited by 5 | Viewed by 2244
Abstract
We developed a 3D, fully self-consistent model for analysis of the ultrashort THz unipolar pulse formation accompanied by its amplification in a nonequilibrium plasma channel induced in nitrogen by a femtosecond UV laser pulse. The model is based on a self-consistent numerical solution [...] Read more.
We developed a 3D, fully self-consistent model for analysis of the ultrashort THz unipolar pulse formation accompanied by its amplification in a nonequilibrium plasma channel induced in nitrogen by a femtosecond UV laser pulse. The model is based on a self-consistent numerical solution of the second-order wave equation in cylindrical geometry and the kinetic Boltzmann equation for the electron velocity distribution function (EVDF) at different points of the spatially inhomogeneous nonequilibrium plasma channel. Rapid relaxation of the electron velocity distribution function in the plasma channel results in the amplification of the leading front of the THz pulse only, while its trailing edge is not amplified or even absorbed, which gives rise to the possibility of the formation of pulses with a high degree of unipolarity. The evolution of the unipolar pulse after its transfer from the channel to open free space is analyzed in detail. Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Photonics)
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11 pages, 2434 KiB  
Article
Polarization-Sensitive Nonlinear Optical Interaction of Ultrashort Laser Pulses with HPHT Diamond
by George K. Krasin, Yulia S. Gulina, Evgeny V. Kuzmin, Victor P. Martovitskii and Sergey I. Kudryashov
Photonics 2023, 10(2), 106; https://doi.org/10.3390/photonics10020106 - 19 Jan 2023
Cited by 6 | Viewed by 2175
Abstract
The filamentation of focused 300 fs laser pulses with variable polarization azimuth in bulk of synthetic HPHT diamond demonstrates the possibility of polarization-dependent bandgap control for crystal dielectric photoexcitation. This directly affects the value of the filamentation threshold power, which exhibits the distinct [...] Read more.
The filamentation of focused 300 fs laser pulses with variable polarization azimuth in bulk of synthetic HPHT diamond demonstrates the possibility of polarization-dependent bandgap control for crystal dielectric photoexcitation. This directly affects the value of the filamentation threshold power, which exhibits the distinct dependence on the polarization azimuth angle. The nonlinear photoluminescence yield, when focusing ultrashort laser pulses with variable polarization in bulk of the synthetic diamond, indicates different polarization-dependent regimes in the dynamics of electron-hole plasma formation, arising due to different processes of photoexcitation and recombination of free carriers during the filamentation process. Thus, at the onset of the filamentation process, at relatively low intensities, the photoluminescence yield rate depends on polarization azimuth controlling bandgap, while at high intensities the resulting dense absorbing plasma exhibits isotropy with respect to laser radiation polarization, and photoluminescence yield weakly depends on polarization azimuth. Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Photonics)
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7 pages, 1403 KiB  
Communication
Reduction in Crosstalk between Integrated Anisotropic Optical Waveguides
by Dmitriy Grudinin, Olga Matveeva, Georgy Ermolaev, Andrey Vyshnevyy, Aleksey Arsenin and Valentyn Volkov
Photonics 2023, 10(1), 59; https://doi.org/10.3390/photonics10010059 - 5 Jan 2023
Cited by 3 | Viewed by 2484
Abstract
The minimization of waveguide crosstalk is a long-standing challenge for optical engineers. Nowadays, the most popular technique to suppress crosstalk is anisotropic nanostructures, realized as subwavelength stripes between waveguides. However, the influence of material anisotropy on the efficiency of such structures remains unknown. [...] Read more.
The minimization of waveguide crosstalk is a long-standing challenge for optical engineers. Nowadays, the most popular technique to suppress crosstalk is anisotropic nanostructures, realized as subwavelength stripes between waveguides. However, the influence of material anisotropy on the efficiency of such structures remains unknown. In this work, we consider MoS2 waveguides separated by MoS2 stripes because this material has the record value of optical anisotropy. We discover that the use of MoS2 instead of Si results in a several-orders-of-magnitude-larger crosstalk distance. Therefore, we envision that by combining the extraordinary material properties with the known crosstalk-suppression methods, one can make the integration density of photonic devices close to electronics. Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Photonics)
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