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Opto-Electronic Advances 2022年第4期5卷 48-68页

作者： Alexey Wolf Alexander Dostovalov Kirill Bronnikov Mikhail Skvortsov stefan wabnitz Sergey Babin Novosibirsk State University Novosibirsk 630090Russia Institute of Automation and Electrometry of the SB RAS Novosibirsk 630090Russia Department of Information Electronics and Telecommunications EngineeringSapienza University of RomeRome 00184Italy

In this article,we review recent advances in the technology of writing fiber Bragg gratings(FBGs)in selected cores of multicore fibers(MCFs)by using femtosecond laser *** writing technology of such a key element as the FBG opens up wide opportunities for the creation of next generation fiber lasers and sensors based on *** advantages of the technology are shown by using the examples of 3D shape sensors,acoustic emission sensors with spatially multiplexed channels,as well as multicore fiber Raman lasers.

关键词： multicore fiber fiber Bragg grating femtosecond laser micromachining fiber laser fiber sensor

Femtosecond nonlinear losses in multimode optical fibers

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Photonics Research 2021年第12期9卷 2443-2453页

作者： MARIO FERRARO FABIO MANGINI MARIO ZITELLI ALESSANDRO TONELLO ANTONIO DE LUCA VINCENT COUDERC stefan wabnitz Department of Information Engineering Electronicsand TelecommunicationsSapienza University of RomeVia Eudossiana 1800184 RomeItaly Department of Information Engineering University of BresciaVia Branze 3825123 BresciaItaly Universitéde Limoges XLIMUMR CNRS 7252123 Avenue A.Thomas87060 LimogesFrance Physics Department University of CalabriaI-87036 Arcavacata di RendeCSItaly CNR Nanotec-Institute of Nanotechnology S.S.CosenzaI-87036 RendeCSItaly CNR-INO Istituto Nazionale di OtticaVia Campi Flegrei 34I-80078 PozzuoliNAItaly

Multimode optical fibers are attracting a growing interest for their capability to transport high-power laser beams,coupled with novel nonlinear optics-based ***,optical fiber breakdown occurs when beam intensities exceed a certain critical *** breakdown associated with irreversible modifications of the refractive index,triggered by multiphoton absorption,has been largely exploited for fiber material *** we show that,for light beam intensities slightly below the breakdown threshold,nonlinear absorption strongly affects the dynamics of a propagating beam as *** experimentally analyze this subthreshold regime and highlight the key role played by spatial self-imaging in graded-index fibers for enhancing nonlinear optical *** characterize the nonlinear power transmission properties of multimode fibers for femtosecond pulses propagating in the near-infrared spectral *** show that an effective N-photon absorption analytical model is able to describe the experimental data well.

关键词： breakdown Femto fibers

Spatiotemporal mode decomposition of ultrashort pulses in linear and nonlinear graded-index multimode fibers

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Photonics Research 2023年第5期11卷 750-756页

作者： MARIO ZITELLI VINCENT COUDERC MARIO FERRARO FABIO MANGINI PEDRO PARRA-RIVAS YIFAN SUN stefan wabnitz Department of Information Engineering Electronics and TelecommunicationsUniversitàdegli Studi di Roma Sapienza00184 RomeItaly Universitéde Limoges XLIMUMR CNRS 725287060 LimogesFrance CNR-INO Istituto Nazionale di Ottica80078 PozzuoliItaly

We develop a spatiotemporal mode decomposition technique to study the spatial and temporal mode power distribution of ultrashort pulses in long spans of graded-index multimode fiber,for different input laser *** find that the beam mode power content in the dispersive pulse propagation regime can be described by the Bose-Einstein law,as a result of the process of power diffusion from linear and nonlinear mode coupling among nondegenerate mode *** the soliton regime,the output mode power distribution approaches the Rayleigh-Jeans law.

关键词： ultrashort multimode mode

Single-shot measurement of wavelength-resolved state of polarization dynamics in ultrafast lasers using dispersed division-of-amplitude

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Photonics Research 2023年第1期11卷 35-43页

作者： QIANG WU LEI GAO YULONG CAO stefan wabnitz ZHENGHU CHANG AI LIU JINGSHENG HUANG LIGANG HUANG TAO ZHU Key Laboratory of Optoelectronic Technology&Systems(Ministry of Education) Chongqing UniversityChongqing 400044China Dipartimento di Ingegneria dell'Informazione Elettronica e TelecomunicazioniSapienza Universitadi Roma00184 RomaItaly CNR-INO Istituto Nazionale di Ottica80078 Pozzuoli(NA)Italy

Characterization of the state of polarization(SOP)of ultrafast laser emission is relevant in several application fields such as field manipulation,pulse shaping,testing of sample characteristics,and biomedical ***,since high-speed detection and wavelength-resolved measurements cannot be simultaneously achieved by commercial polarization analyzers,single-shot measurements of the wavelength-resolved SOP of ultrafast laser pulses have rarely been ***,we propose a method for single-shot,wavelength-resolved SOP measurements that exploits the method of division-of-amplitude under far-field transformation.A large accumulated chromatic dispersion is utilized to time-stretch the laser pulses via dispersive Fourier transform,so that spectral information is mapped into a temporal *** calibrating our test matrix with different wavelengths,wavelength-resolved SOP measurements are achieved,based on the division-of-amplitude approach,combined with high-speed opto-electronic *** a proof-of-concept demonstration,we reveal the complex wavelength-dependent SOP dynamics in the build-up of dissipative *** experimental results show that the dissipative soliton exhibits far more complex wavelength-related polarization dynamics,which are not shown in single-shot spectrum *** method paves the way for single-shot measurement and intelligent control of ultrafast lasers with wavelength-resolved SOP structures,which could promote further investigations of polarization-related optical signal processing techniques,such as pulse shaping and hyperspectral polarization imaging.

关键词： polarization resolved dynamics

Polarization evolution dynamics of dissipative soliton fiber lasers

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Photonics Research 2019年第11期7卷 1331-1339页

作者： Lei Gao Yulong Cao stefan wabnitz Hongqing Ran Lingdi Kong Yujia Li Wei Huang Ligang Huang Danqi Feng Tao Zhu Key Laboratory of Optoelectronic Technology and Systems(Ministry of Education) Chongqing UniversityChongqing 400044China Dipartimento di Ingegneria dell'Informazione Elettronica e TelecomunicazioniSapienza Universita di Roma00184 RomeItaly Novosibirsk State University Novosibirsk 630090Russia

Dissipative solitons emerge as stable pulse solutions of nonintegrable and nonconservative nonlinear physical systems, owing to a balance of nonlinearity, dispersion, and loss/gain. A considerable research effort has been dedicated to characterizing amplitude and phase evolutions in the spatiotemporal dynamics of dissipative solitons emerging from fiber lasers. Yet, the picture of the buildup process of dissipative solitons in fiber lasers is incomplete in the absence of corresponding information about the polarization evolution. Here, we characterize probabilistic polarization distributions in the buildup of dissipative solitons in a net-normal dispersion fiber laser system, mode-locked by single-wall carbon nanotubes. The output optical spectra under different pump powers are filtered by a tunable filter, and are detected by a polarization state analyzer. The laser system operates from random amplified spontaneous emission into a stable dissipative soliton state as the cavity gain is progressively increased. Correspondingly, the state of polarization of each spectral wavelength converges towards a fixed *** reveal the invariant polarization relationship among the various wavelength components of the laser output field, the phase diagram of the ellipticity angle and the spherical orientation angle is introduced. We find that,within the central spectral region of the dissipative soliton, the state of polarization evolves with frequency by tracing a uniform arc on the Poincaré sphere, whereas in the edges of the dissipative soliton spectrum, the state of polarization abruptly changes its path. Increasing cavity gain leads to spectral broadening, accompanied by a random scattering of the state of polarization of newly generated frequencies. Further increases of pump power result in dissipative soliton explosions, accompanied by the emergence of a new type of optical polarization rogue waves. These experimental results provide a deeper insight into the transient d

关键词： soliton dissipative dynamics