Photonics

Editorial

Jump to: Research, Review

4 pages, 160 KiB

Open AccessEditorial

Special Issue “Specialty Optical Fibers, Fiber Lasers and Their Applications”

by Svetlana Aleshkina, Regina Gumenyuk and Serafima Filatova

Photonics 2022, 9(5), 274; https://doi.org/10.3390/photonics9050274 - 19 Apr 2022

Viewed by 1632

Abstract

The unique properties of optical fibers enable the realization of the state-of-the-art fiber lasers, which surpass other laser sources in many characteristics and act themselves as an exceptional platform for harnessing emerging technologies [...] Full article

(This article belongs to the Special Issue Specialty Optical Fibers, Fiber Lasers and Their Applications)

Research

Jump to: Editorial, Review

11 pages, 1453 KiB

Open AccessArticle

Amplification and Generation of Frequency-Modulated Soliton Pulses in Nonuniform Active Fiber Configurations

by Aleksei Abramov, Igor Zolotovskii, Victor Lapin, Pavel Mironov, Marina Yavtushenko, Vyacheslav Svetukhin and Andrei Fotiadi

Photonics 2022, 9(3), 160; https://doi.org/10.3390/photonics9030160 - 06 Mar 2022

Cited by 2 | Viewed by 1787

Abstract

We report on the theoretical and numerical analysis of the nonlinear Schrödinger equation describing the dynamical evolution of frequency-modulated (FM) optical signals propagating through the fiber configuration comprising active fibers with the anomalous dispersion nonuniformly distributed over the fiber length. In our consideration, [...] Read more.

We report on the theoretical and numerical analysis of the nonlinear Schrödinger equation describing the dynamical evolution of frequency-modulated (FM) optical signals propagating through the fiber configuration comprising active fibers with the anomalous dispersion nonuniformly distributed over the fiber length. In our consideration, a single active fiber section including segments with initially increasing and then decreasing dispersion is used for amplification and compression of an external FM pulse resulting in an increase of ~6 orders of magnitude in the pulse peak power and a 100-fold narrowing of the pulse duration down to a few picoseconds. Moreover, we demonstrate that, with a ~1 mW weakly modulated continuous wave input signal, the fiber configuration comprising two active fiber sections with different dispersion profiles is able to generate a strongly periodic pulse train, resulting in a pulse repetition rate >100 GHz, a pulse duration ~0.5 ps, and peak power up to ~1 kW. An evolution of optical signals governed by modulation instability in both fiber configurations is explored. Full article

(This article belongs to the Special Issue Specialty Optical Fibers, Fiber Lasers and Their Applications)

► Show Figures

Figure 1

14 pages, 18958 KiB

Open AccessArticle

Ex-Vivo Exposure on Biological Tissues in the 2-μm Spectral Range with an All-Fiber Continuous-Wave Holmium Laser

by Mariya S. Kopyeva, Serafima A. Filatova, Vladimir A. Kamynin, Anton I. Trikshev, Elizaveta I. Kozlikina, Vadim V. Astashov, Victor B. Loschenov and Vladimir B. Tsvetkov

Photonics 2022, 9(1), 20; https://doi.org/10.3390/photonics9010020 - 30 Dec 2021

Cited by 12 | Viewed by 1896

Abstract

We present the results on the interaction of an all-fiber Holmium-doped laser CW radiation at a wavelength of 2100 nm with soft tissues and compare it with the other results obtained by the most used solid-state laser systems. Ex-vivo single spot experiments were [...] Read more.

We present the results on the interaction of an all-fiber Holmium-doped laser CW radiation at a wavelength of 2100 nm with soft tissues and compare it with the other results obtained by the most used solid-state laser systems. Ex-vivo single spot experiments were carried out on the porcine longissimus muscles by varying the laser impact parameters in a wide range (average output power 0.3, 0.5 and 1.1 W; exposure time 5, 30 and 60 s). Evaluation of the laser radiation exposure was carried out by the size of coagulation and ablation zones on the morphological study. Exposure to a power of 0.3 W (1.5–18 J of applied energy) caused only reversible changes in the tissues. The highest applied energy of 66 J for 1.1 W and a 60-s exposure resulted in a maximum ablation depth of approximately 1.2 mm, with an ablation efficiency of 35%. We have shown that it is not necessary to use high powers of CW radiation, such as 5–10 W in the solid-state systems to provide the destructive effects. Similar results can be achieved at lower powers using the simple all-fiber Holmium laser based on the standard single-mode fiber, which could provide higher power densities and be more convenient to manufacture and use. The obtained results may be valuable as an additional experimental point in the field of existing results, which in the future will allow one to create a simple optimal laser system for medical purposes. Full article

(This article belongs to the Special Issue Specialty Optical Fibers, Fiber Lasers and Their Applications)

► Show Figures

Figure 1

15 pages, 3371 KiB

Open AccessArticle

Changes in Spectral Fluorescence Properties of a Near-Infrared Photosensitizer in a Nanoform as a Coating of an Optical Fiber Neuroport

by Yuliya Maklygina, Igor Romanishkin, Aleksej Skobeltsin, Dina Farrakhova, Sergej Kharnas, Lina Bezdetnaya and Victor Loschenov

Photonics 2021, 8(12), 556; https://doi.org/10.3390/photonics8120556 - 06 Dec 2021

Cited by 1 | Viewed by 1850

Abstract

In this work, we tested a new approach to assess the presence of inflammatory process in the implant area using spectral methods and the technique of fiber fluorescence analysis of photosensitizers in nanoform. First of all, the spectral characteristics of the photosensitizer when [...] Read more.

In this work, we tested a new approach to assess the presence of inflammatory process in the implant area using spectral methods and the technique of fiber fluorescence analysis of photosensitizers in nanoform. First of all, the spectral characteristics of the photosensitizer when interacting with the porous surface of the implant, based on hydroxyapatite under in vitro and in vivo conditions, were determined. Thus, it was shown that spectral characteristics of photosensitizers can be used for judgement on the process of inflammation in the implant area and thus on the local presence of the immunocompetent cells. The analysis was performed at a sufficient depth in the biotissue by using the near-infrared spectral region, as well as two different methods: fiber-based laser spectroscopy and fiber-optic neuroscopy, which served to monitor the process and regular fluorescence diagnosis of the studied area. Fluorescence spectroscopic analysis was performed on experimental animals in vivo, i.e., under conditions of active immune system intervention, as well as on cell cultures in vitro in order to judge the role of the immune system in the interaction with the implant in comparison. Thus, the aim of the study was to determine the relationship between the fluorescence signal of nanophotosensitizers in the near infrared spectral region and its parameters with the level of inflammation and the type of surface with which the photosensitizer interacts in the implant area. Thus, fiber-optic control opens up new approaches for further diagnosis and therapy in the implant area, making immune cells a prime target for advanced therapies. Full article

(This article belongs to the Special Issue Specialty Optical Fibers, Fiber Lasers and Their Applications)

► Show Figures

Figure 1

11 pages, 3574 KiB

Open AccessArticle

Tunable Spacing Dual-Wavelength Q-Switched Fiber Laser Based on Tunable FBG Device

by Nurnazifah M. Radzi, Amirah A. Latif, Mohammad F. Ismail, Josephine Y. C. Liew, Noor A. Awang, Han K. Lee, Fauzan Ahmad, Siti F. Norizan and Harith Ahmad

Photonics 2021, 8(12), 524; https://doi.org/10.3390/photonics8120524 - 23 Nov 2021

Cited by 6 | Viewed by 1625

Abstract

A tunable spacing dual-wavelength Q-switched fiber laser is experimentally demonstrated based on a fiber Bragg grating tunable device incorporated in an erbium-doped fiber laser (EDFL). The system utilizes two identical fiber Bragg gratings (FBGs) at 1547.1 nm origin to enable two laser lines [...] Read more.

A tunable spacing dual-wavelength Q-switched fiber laser is experimentally demonstrated based on a fiber Bragg grating tunable device incorporated in an erbium-doped fiber laser (EDFL). The system utilizes two identical fiber Bragg gratings (FBGs) at 1547.1 nm origin to enable two laser lines operation. The wavelength separations between two laser lines are controlled by fixing one of the FBGs while applying mechanical stretch and compression to the other one, using a fiber Bragg grating tunable device. The seven steps of wavelength spacing could be tuned from 0.3344 to 0.0469 nm spacing. Pulse characteristics for both close and wide spacing of dual-wavelength Q-switched fiber laser are successfully being recorded. The findings demonstrate the latest idea of dual-wavelength fiber laser based on FBG tunable device, which offers a wide range of future applications. Full article

(This article belongs to the Special Issue Specialty Optical Fibers, Fiber Lasers and Their Applications)

► Show Figures

Figure 1

11 pages, 10473 KiB

Open AccessArticle

Er-Doped Tapered Fiber Amplifier for High Peak Power Sub-ns Pulse Amplification

by Maksim M. Khudyakov, Andrei E. Levchenko, Vladimir V. Velmiskin, Konstantin K. Bobkov, Svetlana S. Aleshkina, Mikhail M. Bubnov, Mikhail V. Yashkov, Aleksei N. Gur’yanov, Leonid V. Kotov and Mikhail E. Likhachev

Photonics 2021, 8(12), 523; https://doi.org/10.3390/photonics8120523 - 23 Nov 2021

Cited by 4 | Viewed by 1681

Abstract

A tapered Er-doped fiber amplifier for high peak power pulses amplification has been developed and tested. The core diameter changed from 15.8 µm (mode field diameter (MFD) 14.5 µm) to 93 µm (MFD 40 µm) along 3.7 m maintaining single-mode performance at 1555 [...] Read more.

A tapered Er-doped fiber amplifier for high peak power pulses amplification has been developed and tested. The core diameter changed from 15.8 µm (mode field diameter (MFD) 14.5 µm) to 93 µm (MFD 40 µm) along 3.7 m maintaining single-mode performance at 1555 nm (according to the S²-method, the part of the power of high-order modes does not exceed 1.5%). The amplification of 0.9 ns pulses with spectral width below 0.04 nm up to a peak power above 200 kW (limited by self-phase modulation) with a slope pump-to-signal conversion efficiency of 15.6% was demonstrated. Full article

(This article belongs to the Special Issue Specialty Optical Fibers, Fiber Lasers and Their Applications)

► Show Figures

Figure 1

14 pages, 5479 KiB

Open AccessArticle

Generation of Subpicosecond Pulse Trains in Fiber Cascades Comprising a Cylindrical Waveguide with Propagating Refractive Index Wave

by Aleksei Abramov, Igor Zolotovskii, Vladimir Kamynin, Andrei Domanov, Aleksandr Alekseev, Dmitry Korobko, Marina Yavtushenko and Andrei Fotiadi

Photonics 2021, 8(11), 484; https://doi.org/10.3390/photonics8110484 - 29 Oct 2021

Cited by 2 | Viewed by 1280

Abstract

A cylindrical waveguide structure with the running refractive index wave has been recently demonstrated as a means for the generation of high-repetition-rate pulse trains. The operation mechanism involves a proper combination of the frequency modulation and modulation instability simultaneously experienced by the input [...] Read more.

A cylindrical waveguide structure with the running refractive index wave has been recently demonstrated as a means for the generation of high-repetition-rate pulse trains. The operation mechanism involves a proper combination of the frequency modulation and modulation instability simultaneously experienced by the input continuous wave (CW) signal as it propagates through the cylinder waveguide. Here, we explore the same idea but employ the cylindrical waveguide only as a part of the cascaded optical fiber configuration now comprising both passive and active optical fiber segments. The new system design enables the improved control of the pulse train formation process in the cascaded system elements, relaxes strong requirements for the CW signal power, and provides an additional optical gain for the advanced pulse peak power scaling. In particular, using a low-amplitude, weakly modulated, continuous wave as an input signal we explore and optimize the nonlinear mechanisms underlying its cascaded transformation into the train of kilowatt peak power picosecond pulses. Full article

(This article belongs to the Special Issue Specialty Optical Fibers, Fiber Lasers and Their Applications)

► Show Figures

Figure 1

10 pages, 34656 KiB

Open AccessCommunication

Spatial Beam Self-Cleaning in Bi-Tapered Multimode Fibers

by Xiao-Jun Lin, Yu-Xin Gao, Jin-Gan Long, Jia-Wen Wu, Xiang-Yue Li, Wei-Yi Hong, Hu Cui, Zhi-Chao Luo, Wen-Cheng Xu and Ai-Ping Luo

Photonics 2021, 8(11), 479; https://doi.org/10.3390/photonics8110479 - 27 Oct 2021

Cited by 2 | Viewed by 1891

Abstract

We report the spatial beam self-cleaning in bi-tapered conventional multimode fibers (MMFs) with different tapered lengths. Through the introduction of the bi-tapered structure in MMFs, the input beam with poor beam quality from a high-power fiber laser can be converted to a centered, [...] Read more.

We report the spatial beam self-cleaning in bi-tapered conventional multimode fibers (MMFs) with different tapered lengths. Through the introduction of the bi-tapered structure in MMFs, the input beam with poor beam quality from a high-power fiber laser can be converted to a centered, bell-shaped beam in a short length, due to the strengthened nonlinear modes coupling. It is found that the bi-tapered MMF with longer tapered length at the same waist diameter shows better beam self-cleaning effect and larger spectral broadening. The obtained results offer a new method to improve the beam quality of high-power laser at low cost. Furthermore, it may be interesting for manufacturing bi-tapered MMF-based devices to obtain the quasi-fundamental mode beam in spatiotemporal mode-locked fiber lasers. Full article

(This article belongs to the Special Issue Specialty Optical Fibers, Fiber Lasers and Their Applications)

► Show Figures

Figure 1

11 pages, 1875 KiB

Open AccessArticle

High-Peak Power Frequency Modulation Pulse Generation in Cascaded Fiber Configurations with Inscribed Fiber Bragg Grating Arrays

by Aleksei Abramov, Igor Zolotovskii, Vladimir Kamynin, Victor Prikhodko, Aleksei Tregubov, Dmitrii Stoliarov, Marina Yavtushenko and Andrei Fotiadi

Photonics 2021, 8(11), 471; https://doi.org/10.3390/photonics8110471 - 24 Oct 2021

Cited by 1 | Viewed by 1560

Abstract

We explored the dynamics of frequency-modulated (FM) pulses in a cascaded fiber configuration comprising one active and one passive optical fiber with multiple fiber Bragg gratings (FBGs) of different periods inscribed over the fiber configuration length. We present a theoretical formalism to describe [...] Read more.

We explored the dynamics of frequency-modulated (FM) pulses in a cascaded fiber configuration comprising one active and one passive optical fiber with multiple fiber Bragg gratings (FBGs) of different periods inscribed over the fiber configuration length. We present a theoretical formalism to describe the mechanisms of the FM pulse amplification and pulse compression in such fiber cascades resulting in peak powers up to ~0.7 MW. In combination with the decreasing dispersion fibers, the considered cascade configuration enables pico- and sub-picosecond pulse trains with a sub-terahertz repetition rate and sub-kW peak power generated directly from the continuous optical signal. Full article

(This article belongs to the Special Issue Specialty Optical Fibers, Fiber Lasers and Their Applications)

► Show Figures

Figure 1

9 pages, 3645 KiB

Open AccessCommunication

Phototherapy of Brain Tumours Using a Fibre Optic Neurosystem

by Yuliya Maklygina, Igor Romanishkin, Aleksej Skobeltsin, Dina Farrakhova and Victor Loschenov

Photonics 2021, 8(11), 462; https://doi.org/10.3390/photonics8110462 - 21 Oct 2021

Cited by 2 | Viewed by 1448

Abstract

In this work, a new approach was tested to assess the cellular composition of tissues by time-resolved methods of fluorescence analysis of exogenous and endogenous fluorophores. First of all, the differences in fluorescence kinetics of endogenous fluorophores (coenzymes NADH and FAD) in tumour [...] Read more.

In this work, a new approach was tested to assess the cellular composition of tissues by time-resolved methods of fluorescence analysis of exogenous and endogenous fluorophores. First of all, the differences in fluorescence kinetics of endogenous fluorophores (coenzymes NADH and FAD) in tumour and immunocompetent cells were determined. After that, differences in fluorescence kinetics of photosensitizer 5 ALA-induced protoporphyrin IX were established due to its different metabolism in cells of different phenotypes. Kinetics of photoluminescence of NADH and FAD coenzymes as well as photosensitizer were studied by means of two different methods: time-resolved spectroscopy based on a streak-camera and fibre optic neuroscopy, which served to perform process monitoring and regular fluorescence diagnosis of the probed region. Time-resolved fluorescence microscopy (FLIM) was used as a control technique. Time-resolved spectroscopic fluorescence lifetime analysis was performed on sexually mature female rats induced with glioma C6 brain tumour under in vivo conditions; thus, under conditions where the immune system actively intervenes in the process of oncogenesis. In this regard, the aim of the study was to recognize the cellular composition of the brain tumour tissue, namely the ratio of cancer and immunocompetent cells and their mutual localization. Understanding the role of the immune system thus provides new ways and approaches for further diagnosis and therapy, making tumour-associated immune cells a prime target for modern therapies. Full article

(This article belongs to the Special Issue Specialty Optical Fibers, Fiber Lasers and Their Applications)

► Show Figures

Figure 1

Review

Jump to: Editorial, Research

45 pages, 7464 KiB

Open AccessReview

Towards Ultimate High-Power Scaling: Coherent Beam Combining of Fiber Lasers

by Hossein Fathi, Mikko Närhi and Regina Gumenyuk

Photonics 2021, 8(12), 566; https://doi.org/10.3390/photonics8120566 - 10 Dec 2021

Cited by 19 | Viewed by 11864

Abstract

Fiber laser technology has been demonstrated as a versatile and reliable approach to laser source manufacturing with a wide range of applicability in various fields ranging from science to industry. The power/energy scaling of single-fiber laser systems has faced several fundamental limitations. To [...] Read more.

Fiber laser technology has been demonstrated as a versatile and reliable approach to laser source manufacturing with a wide range of applicability in various fields ranging from science to industry. The power/energy scaling of single-fiber laser systems has faced several fundamental limitations. To overcome them and to boost the power/energy level even further, combining the output powers of multiple lasers has become the primary approach. Among various combining techniques, the coherent beam combining of fiber amplification channels is the most promising approach, instrumenting ultra-high-power/energy lasers with near-diffraction-limited beam quality. This paper provides a comprehensive review of the progress of coherent beam combining for both continuous-wave and ultrafast fiber lasers. The concept of coherent beam combining from basic notions to specific details of methods, requirements, and challenges is discussed, along with reporting some practical architectures for both continuous and ultrafast fiber lasers. Full article

(This article belongs to the Special Issue Specialty Optical Fibers, Fiber Lasers and Their Applications)

► Show Figures

Figure 1

10 pages, 2280 KiB

Open AccessReview

Cascaded Generation in Multimode Diode-Pumped Graded-Index Fiber Raman Lasers

by Alexey G. Kuznetsov, Ilya N. Nemov, Alexey A. Wolf, Ekaterina A. Evmenova, Sergey I. Kablukov and Sergey A. Babin

Photonics 2021, 8(10), 447; https://doi.org/10.3390/photonics8100447 - 15 Oct 2021

Cited by 4 | Viewed by 1583

Abstract

We review our recent experimental results on the cascaded Raman conversion of highly multimode laser diode (LD) pump radiation into the first- and higher-order Stokes radiation in multimode graded-index fibers. A linear cavity composed of fiber Bragg gratings (FBGs) inscribed in the fiber [...] Read more.

We review our recent experimental results on the cascaded Raman conversion of highly multimode laser diode (LD) pump radiation into the first- and higher-order Stokes radiation in multimode graded-index fibers. A linear cavity composed of fiber Bragg gratings (FBGs) inscribed in the fiber core is formed to provide feedback for the first Stokes order, whereas, for the second order, both a linear cavity consisting of two FBGs and a half-open cavity with one FBG and random distributed feedback (RDFB) via Rayleigh backscattering along the fiber are explored. LDs with different wavelengths (915 and 940 nm) are used for pumping enabling Raman lasing at different wavelengths of the first (950, 954 and 976 nm), second (976, 996 and 1019 nm) and third (1065 nm) Stokes orders. Output power and efficiency, spectral line shapes and widths, beam quality and shapes are compared for different configurations. It is shown that the RDFB cavity provides higher slope efficiency of the second Stokes generation (up to 70% as that for the first Stokes wave) with output power up to ~30 W, limited by the third Stokes generation. The best beam quality parameter of the second Stokes beam is close to the diffraction limit (M²~1.3) in both linear and half-open cavities, whereas the line is narrower (<0.2 nm) and more stable in the case of the linear cavity with two FBGs. However, an optimization of the FBG reflection spectrum used in the half-open cavity allows this linewidth value to be approached. The measured beam profiles show the dip formation in the output pump beam profile, whereas the first and second Stokes beams are Gaussian-shaped and almost unchanged with increasing power. A qualitative explanation of such behavior in connection with the power evolution for the transmitted pump and generated first, second and third Stokes beams is given. The potential for wavelength tuning of the cascaded Raman lasers based on LD-pumped multimode fibers is discussed. Full article

(This article belongs to the Special Issue Specialty Optical Fibers, Fiber Lasers and Their Applications)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Specialty Optical Fibers, Fiber Lasers and Their Applications

Share This Special Issue

Special Issue Editors

Special Issue Information

Published Papers (12 papers)

Editorial

Research

Review

Further Information

Guidelines

MDPI Initiatives

Follow MDPI