Optical apparatus (110, 500, 600, 800, 1000) for providing light having a selected 
linear polarization having a polarization ratio, the apparatus (110, 500, 600, 800, 1000) comprising a length of 
optical fiber (120, 504, 604, 804, 1001) comprising a 
rare earth for providing light having a first 
wavelength responsive to receiving pump light having a second 
wavelength that is different than said first 
wavelength, wherein if the length of 
optical fiber (120, 504, 604, 804, 1004) were placed in a first position between the length of 
fiber (120, 504, 604, 804, 1004) is substantially linearly oriented (20) the 
fiber (120, 504, 604, 804, 1004) could propagate at the first wavelength a fundamental mode and a plurality of higher order 
modes and the apparatus (110, 500, 600, 800, 1000) could provide light having a first polarization ratio for the selected 
linear polarization and an M2 parameter, and wherein the length of 
fiber (120, 504, 604, 804, 1004) is positioned in a second position that increases the 
bend loss of the fiber relative to the first position such that, responsive to the increased 
bend loss, the apparatus (110,500, 600, 800, 1000) can provide light having a reduced M2parameter as well as a second polarization ratio for the selected polarization that is increased relative to the first polarization ratio, the increase being at least 6 dB greater than the first polarization ratio, and wherein when the length of fiber (120, 504, 604, 804, 1004) is in the second position the apparatus (110, 500, 600, 800, 1000) can provide a 
slope efficiency that is at least 50% of the ratio of the second wavelength to the first wavelength.