Room Temperature Optical Anisotropy of a LaMnO\u3csub\u3e3\u3c/sub\u3e Thin-Film Induced by Ultra-Short Pulse Laser

We observed ultra-short laser pulse-induced transient optical anisotropy in a LaMnO3 thin film. The anisotropy was induced by laser pulse irradiation with a fluence of less than 0.1 mJ/cm2 at room temperature. The transmittance and reflectance showed strong dependence on the polarization states of the pulses. For parallel and perpendicular polarization states, there exists a difference of approximately 0.2% for transmittance and 0.05% for reflectance at 0.3 ps after the irradiation with a pump pulse, respectively. The theoretical values for optical transmittance and reflectance with an assumption of an orbital ordering of 3d eg electrons in Mn3+ ions showed good agreement with the experimental results, demonstrating that the transient optical anisotropy in LaMnO3 thin film is due to the photo-induced symmetry-breaking of orbital ordering in excited states