Performance of kW class fiber amplifiers spanning a broad range of wavelengths: 1028~1100nm

We present results on the amplifier performance and characteristics of Yb-doped Single Mode fiber amplifiers spanning a broad range of wavelengths from 1028 nm to 1100 nm. Both PM and non-PM amplifiers are discussed, with emphasis on the use of polarization controllers in intrinsically non-PM amplifiers to obtain high Polarization Extinction Ratios (PER). In general, outside the 1064nm region, there has been relatively little discussion or work towards developing high power fiber amplifiers for operation at either 1030 nm or 1100 nm with narrow line-width and high brightness, primarily due to amplifier design and architecture issues related to strong re-absorption and amplified spontaneous emission. Here we address key fiber and amplifier design characteristics aimed at mitigating these issues while highlighting performance attributes and challenges for operation near either end of the above defined spectral range.