Femtosecond-pulse inscribed FBGs for mode selection in multimode fiber lasers

Dostovalov, A. V.; Wolf, Alexey A.; Skvortsov, M. A.; Abdullina, S. R.; Kuznetsov, A. G.; Kablukov, S. I.; Babin, Sergey A.

doi:10.1016/j.yofte.2019.101988

Cited by 21 publications

(12 citation statements)

References 75 publications

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“…The combined pump radiation with total power up to ~ 200 W was coupled into the GIF, in which a laser cavity is formed by a UV-inscribed highly-reflective (R ~ 90%) FBG at the input end, with output coupler (OC) based on fs-inscribed FBG (R ~ 4%) with angled cleaved fibre end. Femtosecond point-by-point writing technology offering new opportunities for multimode fibres 27 was used to create a 2nd-order FBG in the near-axis area (~ 5 µm) of the graded-index core, see microscope image in Fig. 1 .…”

Section: Methodsmentioning

confidence: 99%

“…The output beam quality approaches the diffraction limit 24 , whereas the output power can be at kilowatt levels in all-fibre amplifier and laser configurations 25 , 26 . One of the key elements of multimode RFLs is the fibre Bragg grating (FBG) with spatially tailored structure, which became possible thanks to the femtosecond (fs) inscription technology 27 . Therefore, multimode RFLs become a very attractive class of CW high-power fibre lasers, potentially free of drawbacks inherent to rare-earth-doped fibre lasers such as: limited wavelength range, photo-darkening, and transverse-mode instability 10 , 15 .…”

Section: Introductionmentioning

confidence: 99%

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Spatio-spectral beam control in multimode diode-pumped Raman fibre lasers via intracavity filtering and Kerr cleaning

Babin

Кузнецов

Sidelnikov

et al. 2021

Sci Rep

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Multimode fibres provide a promising platform for boosting the capacity of fibre links and the output power of fibre lasers. The complex spatiotemporal dynamics of multimode beams may be controlled in spatial and temporal domains via the interplay of nonlinear, dispersive and dissipative effects. Raman nonlinearity induces beam cleanup in long graded-index fibres within a laser cavity, even for CW Stokes beams pumped by highly-multimode laser diodes (LDs). This leads to a breakthrough approach for wavelength-agile high-power lasers. However, current understanding of Raman beam cleanup is restricted to a small-signal gain regime, being not applicable to describing realistic laser operation. We solved this challenge by experimentally and theoretically studying pump-to-Stokes beam conversion in a graded-index fibre cavity. We show that random mode coupling, intracavity filtering and Kerr self-cleaning all play a decisive role for the spatio-spectral control of CW Stokes beams. Whereas the depleted LD pump radiation remains insensitive to them.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Spatio-spectral beam control in multimode diode-pumped Raman fibre lasers via intracavity filtering and Kerr cleaning

Babin

Кузнецов

Sidelnikov

et al. 2021

Sci Rep

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“…In this situation, FBG can be used as an all-fiber mode selector when combined with a wavelength selector (i.e., volume FBG or acousto-optical filter). Point-by-point fabrication of multimode FBG by femtosecond lasers offers an opportunity to tailor the FBG transverse profile with high spatial resolution [62,387].…”

Section: High-power Fbg: From Resonator To Spectral-spatial Filteringmentioning

confidence: 99%

Functional Fibers and Functional Fiber-Based Components for High-Power Lasers

et al. 2022

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The success of high-power fiber lasers is fueled by maturation of active and passive fibers, combined with the availability of high-power fiber-based components. In this contribution, we first overview the enormous potential of rare-earth doped fibers in spectral coverage and recent developments of key fiber-based components employed in high-power laser systems. Subsequently, the emerging functional active and passive fibers in recent years, which exhibit tremendous advantages in balancing or mitigating parasitic nonlinearities hindering high-power transmission, are outlined from the perspectives of geometric and material engineering. Finally, novel functional applications of conventional fiber-based components for nonlinear suppression or spatial mode selection, and correspondingly, the high-power progress of function fiber-based components in power handling are introduced, which suggest more flexible controllability on high-power laser operations. Graphical abstract

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“…One can see that a significant reduction in the output beam size and corresponding improvement in the beam quality M 2 occurs at each stage of the pump to the first and second Stokes beam conversion. This improvement is mainly defined by the mode-selective properties of fsinscribed FBGs, in which the modified refractive index is localized in a small area of 1 × 8 µm near the GIF core center, thus providing predominant reflection of the fundamental mode; see [18] for more details. The reflection spectra of the 976 and 1019 nm FBG pairs employed in the scheme with 940 nm pump LDs are shown in Figure 2a,b.…”

Section: Schemes Of the Cascaded Raman Lasers Based On Multimode Fibermentioning

confidence: 99%

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

et al. 2021

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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.

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Femtosecond-pulse inscribed FBGs for mode selection in multimode fiber lasers

Cited by 21 publications

References 75 publications

Spatio-spectral beam control in multimode diode-pumped Raman fibre lasers via intracavity filtering and Kerr cleaning

Spatio-spectral beam control in multimode diode-pumped Raman fibre lasers via intracavity filtering and Kerr cleaning

Functional Fibers and Functional Fiber-Based Components for High-Power Lasers

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

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