SEE PROFILE

Using a large mode area, ytterbium-doped cladding-pumped fiber and a novel cavity configuration we obtain 2.3 mJ Q-switched pulses, a record pulse energy for a fiber laser. Average powers in excess of 5W were achieved. We present a Q-switched, cladding-pumped, ytterbium-doped, large mode area (LMA) fiber laser at 1090 nm capable of generating a record-breaking 2.3 mJ of output pulse energy at 500 Hz repetition rate and over 5 W of average output power at higher repetition rates in a high-brightness beam (M2 = 3). A similar fiber generated> 0.5 mJ pulses in a diffraction-limited beam. For the highest pulse energies we recycle amplified spontaneous emission (ASE) at 1035 nm. Our results represent a three-fold increase in pulse energy over previously published Q-switched fiber lasers, and firmly establish fiber lasers as compact, multi-watt, multi-millijoule pulse sources with large scope for scientific and industrial applications. The fiber was made in-house and has a rectangular inner cladding of pure silica (175 ́ 350 mm) and a silicone rubber outer-cladding providing an inner cladding NA of 0.4. The aluminosilicate LMA-core (Fig. 2) is centered in the cladding. It has an NA of 0.075 and a diameter of 44 mm, offering a larg