title: Residual-stress relaxation and densification in CO2-laser-induced long-period fiber gratings.
abstract: The first concurrent measurements of the three-dimensional refractive-index and residual-stress distributions in a CO(2)-laser-irradiated fiber are presented. A Corning SMF-28 fiber was exposed from one side to focused pulses with durations of 100-500 ms. The cross-sectional form of the index modulation is asymmetric with changes concentrated on the side of the fiber facing the exposure. The longitudinal form is Gaussian-like with a wide top and extends approximately 100  μm from the center of the exposure. Relaxation of frozen-in viscoelasticity results in a maximum index modulation of 5×10(-4) on the side of the fiber facing the exposure with mechanical stress relaxation contributing changes of less than 1×10(-4).
authors.affiliation: School of Electrical and Computer Engineering, Georgia Institute of Technology, 777 Atlantic Drive NW, Atlanta, Georgia 30332-0250, USA. mrhutsel@gatech.edu
authors.forename: Michael R
authors.initials: MR
authors.lastname: Hutsel
authors.forename: Thomas K
authors.initials: TK
authors.lastname: Gaylord