We present experimental studies of a novel polarization-maintaining (PM) Yb-doped photonic crystal fiber (PCF) possessing a two-segment transverse acoustic profile and a mode field diameter (MFD) of approximately 30 μm. The concentrations of the dopants (fluorine, aluminum, germanium) in the two segments were selected such that the corresponding Brillouin shifts were sufficiently separated to allow for the introduction of a large thermal gradient for further SBS suppression. A pump-probe experiment was conducted in order to characterize the Brillouin gain spectrum (BGS) and to confirm the existence of two narrow Brillouin gain peaks. The separation of the two peaks was approximately 220 MHz and the bandwidth of each was estimated to be 50 MHz. The application of a step temperature profile resulted in the BGS displaying four distinct peaks; thus demonstrating further SBS suppression through a thermal gradient. By utilizing the thermal gradient obtained through quantum defect heating, we obtained 494 W of output power in a counter-pumped configuration without the onset of SBS. Measurements of the beam quality at various power levels and up to the highest reported power consistently indicated an M2 of less than 1.3.© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.