Resonantly cladding-pumped Yb-free Er-doped LMA fiber laser with record high power and efficiency

Abstract

We report the results of our power scaling experiments with resonantly cladding-pumped Er-doped eye-safe large mode area (LMA) fiber laser. While using commercial off-the-shelf LMA fiber we achieved over 88 W of continuous-wave (CW) single transverse mode power at ~1590 nm while pumping at 1532.5 nm. Maximum observed optical-to-optical efficiency was 69%. This result presents, to the best of our knowledge, the highest power reported from resonantly-pumped Yb-free Er-doped LMA fiber laser, as well as the highest efficiency ever reported for any cladding-pumped Er-doped laser, either Yb-co-doped or Yb-free.

Highly Doped Phosphate Glass Fibers for Compact Lasers and Amplifiers: A Review

“…This transition forms a three-levels system for which a high pump power is required to obtain a population inversion and thus reach the threshold. The most common pumping arrangement is based on the transition 4 I15/2 → 4 I11/2 with a wavelength of around 980 nm, although in-band pumping ( 4 I15/2 → 4 I13/2, e.g., at 1.45 µm) is also possible [28,29]. This transition is widely exploited in Er 3+ -doped fiber amplifiers (EDFAs).…”

Single frequency 1560nm Er:Yb fiber amplifier with 207W output power and 50.5% slope efficiency

“…Resonant pumping has shown higher optical efficiencies without the need for Yb co-doping, thus eliminating the parasitics. However, even longer fiber lengths are required due to pump bleaching effects [1][2]. This can be problematic for single frequency power scaling due to Stimulated Brillouin Scattering (SBS) limitations [5].…”

“…However, several issues, such as bottlenecking of the energy transfer, as well as the quantum inefficiency, have limited significant power scaling of these co-doped fibers [3][4]. To overcome this limitation, resonant pumping has been demonstrated, with high efficiency [1][2]. However, this approach requires a 1470-1535nm pump source and a long length of fiber to overcome bleaching effects.…”

“…The long fiber length can limit the power scaling for single frequency applications. In addition, 1470-1535nm pump sources are either fiber-based (via Raman conversion) or diode-based with low brightness [1][2]. Although this approach can be beneficial for very high power scaling due to the low quantum defect, the long fiber length can limit the overall efficiency for moderate power applications.…”

“…Although this helps the pump absorption, it also creates a problem with parasitic lasing of the Yb ions under strong pumping conditions, which generally limits output power. Other pump schemes have shown high efficiency through resonant pumping of erbium only without the need for Yb as a sensitizer [1][2]. Although this can enable higher power scaling due to a decrease in the thermal loading, resonant pumping methods require long fiber lengths due to pump bleaching, which may limit the power scaling which can be achieved for single frequency output.…”