Sub-milliwatt sub-millisecond recording of population gratings in ytterbium-doped optical fibers at 976 nm

We report effective formation of population gratings in ytterbium-doped fibers by coherent light at 976 nm, i.e. at the wavelength that is typically utilized for optical pumping of these fibers. The dynamic gratings need sub-mW cw laser power to be recorded and have comparable amplitude (absorption) and phase (refractive index) components. Given the spontaneous relaxation time of a Yb3+ meta-stable level of -0.8 ms, the grating formation time proved also to be in the sub-ms region with the phase grating component significantly slower than the amplitude one. (C) 2011 Elsevier B.V. All rights reserved.