Investigations of single-frequency Raman fiber amplifiers operating at 1178 nm

Abstract

We report on core-pumped single-stage and two-stage polarization-maintaining single-frequency Raman fiber amplifiers (RFAs). For a counter-pumped single-stage RFA, commercial-off-the shelf (COTS) single-mode fiber was utilized to generate 10 W of output power at 1178 nm through the application of a two-step thermal gradient in order to suppress SBS. The relatively high output can be explained by the Brillouin gain spectrum (BGS) of the COTS fiber. A pump-probe characterization of the BGS of the fiber provided a Brillouin gain coefficient of 1.2 × 10(-11) m/W with a FWHM of 78 MHz for the gain bandwidth. A fiber cutback study was also conducted to investigate the signal output at SBS threshold as a function of pump power for optimal length. This study revealed a linear dependence, which is in agreement with the theoretical prediction. Furthermore, we present numerical simulations indicating that substantial power scaling can be achieved by seeding at a higher power. Consequently, we constructed a two-stage RFA in order to achieve seed powers at the 1 W level. By utilizing an acoustically tailored fiber possessing a lower Brillouin gain coefficient than the COTS fiber and by seeding at higher powers, 22 W of single-frequency 1178 nm output was obtained from a counter-pumped two-stage RFA. Finally, we show that the single-frequency spectral bandwidth could not be maintained when a similar co-pumped two-stage RFA was utilized.

Single-frequency Raman fiber amplifier emitting 11 μj 150 W peak-power at 1645 nm for remote methane sensing applications

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

“…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.…”

“…A 24.3 W 589 nm laser was created from this by using an external resonant doubling cavity. Also, 22 W of single-frequency 1178 nm was obtained from a counter-pumped two-stage Raman fiber amplifier using an acoustically tailored fiber 13 . Finally, 24.6 W of single-frequency 1178 nm has been obtained from a ytterbium-doped photonic band gap fiber laser with a 320 kHz linewidth 14 .…”

1150-nm Yb-Doped Fiber Laser Pumped Directly by Laser-Diode With an Output Power of 52 W

“…There are several approaches to achieve L-band lasers. For example, Raman fiber laser (RFL) could be a good method to achieve L-band lasers [17]- [19], but the structure of RFL is complex and the whole efficiency is low relatively. Something must be mentioned that, bismuth-doped fibers draw people's attention to emitting lasers in the range 1150-1215 nm, because they can fill the gap of emission range between Yb-doped and Er-doped fibers [20].…”