Time-resolved Optical Study of Charge-ordered Manganites.*

We study the effects of applied electric fields and large magnetic fields on the optical properties of Pr$_{(1-x)}$Ca$_{x} $MnO$_{3}$ (x$\sim $0.5) (PCMO) and La$_{(1-x)}$Ca$_{x}$MnO$_{3} $ (x$\sim $0.18) (LCMO) using time-resolved techniques. Our measurements are performed down to 4 K and in dc magnetic fields up to 31 T. The conductivity of the low-temperature strong charge/orbital ordering in PCMO is altered by the application of an electric field and a magnetic field. We demonstrate that time- resolved optical reflection and Kerr effect measurements are capable of capturing these mixed electronic and magnetic effects to gain further insight into the change of the ordering.