Second-harmonic generation of light in ferroelectric polymer films with a spatially nonuniform distribution of polarization

In the present work, the author addresses the problem of whether it is possible to decide with second harmonic generation experiments if a given pyroelectric polymer film has a homogeneous distribution of polarization and how the limitations of second harmonic generation can be simply overcome by quasi-phase matching techniques and by optical resonance enhancement. A spatial distribution of the spontaneous polarization P_s(z) results in a similar spatial distribution of the nonlinear optical coefficients d ₃₁(z) and d₃₃(z). It is shown that the generated second harmonic power from a nonlinear slab is sensitive to this distribution of d₃₁ and d ₃₃. It is further shown that the limitations of second harmonic generation which are due to the coherence length can be overcome by quasi-phase-matching and optical resonance enhancement for the fundamental or the harmonic beams