Mode field profile and polarization dependence of long period fiber gratings written by CO2 laser

Mode field profiles and polarization dependence in the CO2-laser-notched long period fiber gratings (LPFGs) were investigated in detail. Asymmetric field profile was demonstrated in the 2- and 3-dimensional far field patterns of the CO2-laser-notched LPFG, which experimentally verifies the previously-presented asymmetry of refractive index modulation within the cross section of the gratings. Polarization dependent loss (PDL) of the LPFG was measured via Mueller matrix method. The maximum PDL of 1.68 dB and the maximum polarization extinction ratio of 1.07 dB are observed in the LPFG.