Time-resolved x-ray diffraction study of photoinduced strains in $h-LuFeO_{3}$ thin film*

We have studied the structural response of epitaxially stabilized h-LuFeO3 (0001) thin film to above-band-gap optical excitation (pump) using time-resolved x-ray diffraction (probe) at picosecond time scale. The shift in (004) Bragg peak induced by a 390 nm excitation (30 ps duration) has been studied as a function of pump fluence and pump-probe time delay. The out-of-plane photoinduced lattice strain $(\Delta c/c)$ exhibits a non-linear relation with fluence. The relaxation time is on the order of 1 ns. These observations suggest a relaxation mechanism that may be mediated by combined effects of charge recombination and phonon relaxation.