SECOND HARMONIC GENERATION IN THE CENTROSYMMETRIC ANTIFERROMAGNET LaFeO3

The paper presents the results of experimental and theoretical studies of nonlinear optical properties of LaFeO3 thin film, which is antiferromagnetic and centrosymmetric, the latter provides prohibition of second harmonic generation in electric-dipole approximation. Spectroscopic studies have shown the presence of the resonant frequency in the spectrum of optical second harmonic generation (SHG) at the pump photon energy 2ћω ≈ 2.85 eV. Comparison of SHG and absorption spectra at the second harmonic wavelength, the new characteristics have been identified, related to the presence of the electronic transition which results in the resonance spectral dependence. The models were suggested for the description of the polarization dependency for the two pump laser wavelengths (non-resonant 800 nm and resonant 860 nm), as well as for the calculation of the nonlinear susceptibility tensor components. The magnetically induced SHG was observed for the conditions of maximal suppression of crystallographic (electric dipole- or electric quadruple) contribution obtained by choice of appropriate polarization rules for the pump and second harmonic waves