In the case of doped polymer system SHG efficiency is proportional to the concentration and orientation degree of NLO-active molecules. Unfortunately, corona poling realised at elevated temperatures causes concentration decrease of NLO-active molecules due to crystallization. On the basis of our studies of the film optical images, refractive index and SHG measurements of the dimethylaminobenzylidene 1,3-indandione and PMMA guest-host system, we have demonstrated that optical quality is improved and second order NLO efficiency is higher, when the external poling electric field is switched on from, the very beginning of the sample heating process.