Efficient low-brightness-pumped Raman amplification of a single high-order Bessel-mode in 335-m of 70-μm-diameter silica-core step-index fiber

Abstract

We experimentally demonstrate Raman amplification of signal pulses in a high-order Bessel mode (LP06) at a wavelength of 1121 nm in a 335-m step-index fiber with a 70-μm diameter, 0.227-NA pure-silica core. This was pumped by 5-ns multimode pulses at 1065 nm from an Yb-doped fiber MOPA. The mode purity of the amplified pulses is well preserved to 23 dB of average-power gain, to 774 W of peak power in 2 ns pulses at 20 kHz repetition rate, when pumped with a peak power of 942 W. The pump depletion as averaged over the signal pulses reaches 59%. We believe that this is the first demonstration of stable mode propagation and Raman amplification of a single Bessel-like higher order mode in a fiber of hundreds of meters. This shows the potential for efficient power scaling of a single signal mode with low-brightness pumping, comparable with that from continuous-wave multimode diode lasers.

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Identifiers

ORCID for Sheng Zhu: orcid.org/0000-0002-4256-6307

ORCID for Yutong Feng: orcid.org/0000-0002-6839-2106

ORCID for Johan Nilsson: orcid.org/0000-0003-1691-7959

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