Stimulated-Brillouin-scattering-suppressed high-power single-frequency polarization-maintaining Raman fiber amplifier with longitudinally varied strain for laser guide star

Background: Liquid filled hollow core fiber Raman wavelength converters are devices enabling to red-shift the wavelength of laser beams delivered by either fixed wavelength or tunable lasers. Most of the reported converters operate in a pulsed regime with pulse durations comprised between a few hundreds of picoseconds and up to a few nanoseconds, and energy of a few micro-Joules. However, and depending on the pulse duration, the optimization of Raman converters turns to be rather challenging since the desired forward Raman scattering may compete with counter-propagating nonlinear effects like Raman and Brillouin back-scatterings. The Brillouin back-scattering is especially hard to cancel since the Brillouin gains are usually larger than the Raman gains. Techniques have already been investigated but are not fully satisfactory. Our aim in this paper is to propose a technique to optimize the Raman forward scattering and to minimize these back-scattering effects. Methods: We compare the interaction lengths in the forward and backward directions in the above-mentioned temporal regimes. If the fiber length is higher that the backward effective length of interaction then the backward effects should decrease at the benefit of the forward Raman scattering. Numerical simulations enable to estimate more precisely how long the fiber should be to get large Raman conversion efficiency and negligible Brillouin scattering. Results and discussion: To validate this technique we build two identical Raman converters differing only by the fiber lengths (0.5 m and 1.5 m). We present the experimental setup. The experimental results are confronted to the numerical simulations. As expected increasing the fiber length strongly decreases the Brillouin scattering. Conclusions: We have proposed a simple and efficient solution to minimize Brillouin back-scattering in Raman wavelength converters by optimizing the fiber length. The experimental demonstration was conducted with low energy (≈ 6 μJ) but the energies should scale with the fiber effective area if more energy is needed, without affecting the conversion efficiencies.

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“…3. Brillouin reduction by broadening the Brillouin spectrum [21][22][23]. This technique was designed for fiber Raman converters.…”

Section: Reduction Of the Backward Brillouin Scatteringmentioning

confidence: 99%

Lowering backward Raman and Brillouin scattering in waveguide Raman wavelength converters

Huy

Delaye

Pauliat

et al. 2017

J. Eur. Opt. Soc.-Rapid Publ.

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“…Current narrow linewidth sodium guidestar lasers are either constructed using slab [1][2][3] or fiber laser technology [4][5][6][7][8][9][10][11][12][13][14] . Slab technology generally involves sum-frequency mixing of 1064 and 1319 nm in a lithium triborate crystal to obtain 589 nm.…”

Section: Introductionmentioning

confidence: 99%

“…The ESO reported achievement of 39 W of narrow linewidth 1178 nm or 26.5 W of 589 nm when frequency doubled. More recently, 44 W of 1 MHz linewidth 1178 nm continuous wave light was obtained by Raman amplification of a distributed feedback diode laser in a variably strained polarizationmaintaining fiber with a record-high optical efficiency of 52% when pumped with a linearly polarized 1120 nm fiber laser 11,12 . Because of the all-polarization maintaining configuration, a polarization extinction ratio of 30 dB was obtained and a 20 time's reduction in the effective stimulated Brillouin scattering coefficient was achieved.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the impact of fiber Bragg grating bandwidth on the efficiency of a Raman resonator

2015

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Significant spectral power leakage was found to occur around the high reflectivity fiber Bragg gratings (FBGs) defining a 1121 nm Raman resonator cavity comprised of PM 10/125 germanosilicate fiber. This cavity was part of a Raman system pumped with broad linewidth 1069 nm and seeded with narrow linewidth 1178 nm. The 1069 nm upon entering the resonator cavity was Raman converted to 1121 nm which then amplified the 1178 nm as it passed through the cavity. Spectral leakage of 1121 nm light from the resonator cavity resulted in sub-optimal amplification of 1178 nm which forced usage of longer resonator cavities having a decreased threshold for Stimulated Brillouin Scattering. Upon study of 1121 nm linewidth broadening as a function of resonator length for cavities employing 3 nm FBGs, differences in the percentage of 1121 nm power spectrally leaking past the output FBG as a function of the 1121 nm intracavity power propagating in the forward direction are not experimentally discernible for resonator cavities longer than 40 m. But, for cavity's shorter than 40 m, the percentage of 1121 nm power spectrally leaking past the output FBG decreased significantly for similar 1121 nm intracavity power levels. For all cavity lengths, a nearly linear relationship exists between percent 1121 nm power leakage and intracavity power levels. Also, cavities employing broader bandwidth FBGs experience less 1121 nm power leakage for similar 1121 nm intracavity power levels. Finally, modeling predictions of Raman system performance are greatly improved upon usage of experimentally derived effective FBG reflectivities.

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“…Single frequency Raman fiber amplifier has been proved to be promising technology for generating compact and efficient 589 nm lasers [1][2][3].…”

Section: Introductionmentioning

confidence: 99%

Over 50 W 589 nm single frequency laser by frequency doubling of single Raman fiber amplifier

et al. 2014

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Stimulated-Brillouin-scattering-suppressed high-power single-frequency polarization-maintaining Raman fiber amplifier with longitudinally varied strain for laser guide star

Cited by 82 publications

References 14 publications

Lowering backward Raman and Brillouin scattering in waveguide Raman wavelength converters

Lowering backward Raman and Brillouin scattering in waveguide Raman wavelength converters

Investigation of the impact of fiber Bragg grating bandwidth on the efficiency of a Raman resonator

Over 50 W 589 nm single frequency laser by frequency doubling of single Raman fiber amplifier

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