Efficient formation of a χ(2) grating in a germanosilicate fibre containing nitrogen

A χ⁽²⁾ grating, capable of converting light to the second harmonic with an efficiency of 2%, was formed for the first time in a germanosilicate optical fibre doped with nitrogen and prepared by the method of surface plasma-chemical vapour deposition. A comparison was made of the properties of this grating with those of chi;⁽²⁾ gratings formed in a germanosilicate fibre free of nitrogen. The high efficiency of the conversion processes, observed when a χ⁽²⁾ grating was formed in a nitrogen-doped fibre, indicated the existence of fast-relaxing photocentres associated with nitrogen and accelerating growth of a χ⁽²⁾ grating in the presence of phase fluctuations of laser radiation.