Mid-infrared fiber lasers at and beyond 35 μm using dual-wavelength pumping

Abstract

We report the first, to the best of our knowledge, erbium-doped zirconium-fluoride-based glass fiber laser operating well beyond 3 μm with significant power. This fiber laser achieved 260 mW in CW at room temperature. The use of two different wavelength pump sources allows us to take advantage of the long-lived excited states that would normally cause a bottleneck, and this enables maximum incident optical-to-optical efficiency of 16% with respect to the total incident pump power. Both output power and efficiency are an order of magnitude improvement over similar lasers demonstrated previously. The fiber laser operating at 3.604 μm also exhibited the longest wavelength of operation obtained to date for a room temperature, nonsupercontinuum fiber laser.

New energy-transfer upconversion process in Er^3+:ZBLAN mid-infrared fiber lasers

“…The impact of this ET process was reduced in recent work [3,4] that used lower doping densities and double clad fibers which resulted in lower population densities at the 4 F 9/2 and 4 I 11/2 states. The combination of this and increased P 1 power removed the laser power saturation that was observed in our earlier work [2].…”

“…In a previous publication we demonstrated that dual wavelength pumping (DWP) could significantly increase the efficiency of erbium doped ZBLAN glass fiber lasers that operate on the 3.5 µm transition. We reported a continuous-wave (CW) output power in excess of 250 mW which was the first room temperature rare-earth doped fiber laser to produce more than 10 mW well beyond 3 µm [2]. Recently two groups have reported over 1 W of power at 3.5 µm using this approach [3,4].…”

Recent Advances in 3.5 μm Erbium-Doped Mid-Infrared Fiber Lasers

“…This technique offers the additional benefit of using infrared pump wavelengths that are more readily available at higher powers than the visible sources required for direct ground state pumping. Our initial work demonstrated this concept on the 4 F 9/2 → 4 I 9/2 transition in erbium [21], [25], [26]. Our first demonstration of mid-infrared DWP laser significantly surpassed the 10 mW barrier, achieved a slope efficiency of 25 % and brought the 3.5 µm Er 3+ transition onto the trend line shown in Fig.…”

Versatile and widely tunable mid-infrared erbium doped ZBLAN fiber laser

“…Figure 2 schematically shows the energy level diagram of the lowest five levels of the erbium ion, the two lasing transitions relevant to this work and the two pump wavelengths. In an earlier work [9], we showed that DWP is an efficient means of generating emissions from the 3.5 μm band transition of erbium. A population of ions is established in the metastable 4 I 11∕2 level by the absorption of P 1 photons on the 974 to 985 nm ground state absorption band.…”

“…After this review was written, a Raman fiber laser produced 50 mW at 3.34 μm [8]. Recently, we introduced an optical pumping method that allows the use of mature, well developed near-infrared sources to excite high lying energy levels of rare earth ions [9]. In this work, we demonstrated that dual wavelength pumping (DWP) could significantly increase the efficiency of erbium doped ZBLAN glass fiber lasers that operate on the 4 F 9∕2 → 4 I 9∕2 transition at 3.5 μm.…”