167 W, power scalable ytterbium-doped photonic bandgap fiber amplifier at 1178 nm.

An ytterbium-doped photonic bandgap fiber amplifier operating at the long wavelength edge of the ytterbium gain band is investigated for high power amplification. The spectral filtering effect of the photonic bandgap efficiently suppresses amplified spontaneous emission at the conventional ytterbium gain wavelengths and thus enables high power amplification at 1178 nm. A record output power of 167 W, a slope efficiency of 61% and 15 dB saturated gain at 1178 nm have been demonstrated using the ytterbium-doped photonic bandgap fiber.