Second harmonic generation study of internally-generated strain in bismuth-substituted iron garnet films.

The present article highlights the lattice-imperfection and compositional origins of the nonlinear optical response in bismuth-substituted iron garnet films. In particular the roles of lattice mismatch strain and micro-strain on second harmonic generation in (Bi,Y)(3)(Fe,Ga)(5)O(12) films are elucidated based on experimental findings. It is found that lattice mismatch strain drives the second harmonic signal in (Bi,Y)(3)(Fe,Ga)(5)O(12) films, in agreement with theoretical predictions; however micro-strain was found not to correlate significantly with the second harmonic signal at the micro-strain levels present in these samples. The present study also elaborates on the influence of the film's constitutive elements and finds the nonlinear response to increase with yttrium concentration.