Cladding-pumped 70-kW-peak-power 2-ns-pulse Er-doped fiber amplifier

Abstract

An all-fiber pulsed erbium laser with pulse width of 2.4 ns working in a MOPA configuration has been created. Cladding pumped double clad erbium doped large mode area fiber was used in the final stage amplifier. Peculiarity of the current work is utilization of custom-made multimode diode wavelength stabilized at 981±0.5 nm -wavelength of maximum absorption by Er ions. It allowed us to shorten Er-doped fiber down to 1.7 m and keep a reasonably high pump-to signal conversion efficiency of 8.4%. The record output peak power for all-fiber amplifiers of 84 kW was achieved within 1555.9±0.15 nm spectral range.

Efficient extraction of high pulse energy from partly quenched highly Er3+-doped fiber amplifiers

“…Although we have deliberately selected an EDF that is partly quenched for our studies, similar Er 3+ -concentrations are possible with less quenching, as demonstrated with a P2O5:Al2O3:SiO2 glass matrix [11] (we estimate the fraction of unsaturable absorption to be half of that in our fiber). This allowed for pulse amplification with relatively high efficiency (8.4%) in a 1.7-m long EDF with a 35-μm core to 84 kW in 2-ns pulses [11] (energy extraction ~0.1 μJ/μm 2 /m).…”

“…In the absence of quenching, high-energy pulse amplification in rare-earth-doped fiber amplifiers, including EDFAs, is well understood [1][2][3][4][5][6][7][8][9][10][11]17,[45][46][47][48]. In the unquenched case, amplified spontaneous emission (ASE) or spurious lasing limits the energy that can be extracted (E extractable ) in a high-energy signal pulse to a few times the intrinsic saturation energy E IS , or say, at most 10 times [46][47][48] if the stored energy and the extraction efficiency are both at their practical limits.…”

“…The strengths of these types of parasitic interactions depend on the distance between the Er 3+ -ions in different ways, and at low concentrations, the separation between Er 3+ -ions can be large enough to make quenching negligible. Tailored host glasses, e.g., co-doped with Al 2 O 3 or P 2 O 5 [11,[14][15][16]49], as well as nanoparticle doping [40,41,[50][51][52][53] can also counteract quenching, but it still reappears gradually at higher concentrations.…”

“…Erbium-doped fiber amplifiers (EDFAs) and lasers enable versatile and compact optical sources in the wavelength range of ∼1.5-1.6 µm (e.g., [1][2][3][4][5][6][7][8][9][10][11]), and can readily be cladding-pumped with over 100 W of power from 980-nm diode lasers at low cost. Their wavelength range offers good atmospheric transmission and relative "eye-safety", highly desirable for LIDAR [2,10,12], remote sensing, and imaging [13].…”

Estimation and Management of Performance Limiting Factors in the Development of 1 kW Peak Power Pulsed Fiber MOPA at 1550 nm

“…This paper describes the methodology for the estimation and management of these limiting factors for each amplifier stage. The work presented here is limited to the fibers which are commercially easily available, unlike customised Ybfree LMA erbium-doped fibers as mentioned in [4][5][6][7] or multifilament core fibers 7 . Inclusion of bulk optics such as gratings 8 shall be also avoided to have a robust all-fiber configuration.…”