Experimental Determination of Space-Charge Electric Field in Photorefractive Multiple Quantum Wells

We present a method for deducing the space-charge electric field in a photorefractive multiple quantum wells (PRQW) illuminated by two coherent beams under drift-current dominant conditions where the phase difference between the space-charge electric field and light intensity is predicted to be $\pi $ radians. Firstly, we determine a relation J$_{0}$(E$_{0}$,I$_{0})$ for the device between the total current J$_{0}$, constant applied electric field E$_{0}$ and uniform intensity I$_{0}$. When the intensity inside the PRQW varies sinusoidally, substituting current for J$_{0}$ and maximum intensity for I$_{0}$ in J$_{0}$(E$_{0}$,I$_{0})$ yields E$_{0}$, which corresponds to the minimum of the net electric field under the assumption that intensity is uniform near maxima and minima. A similar procedure is used to deduce the maximum value of the net electric field inside PRQW. Subtracting the applied electric field from the net electric field yields the space-charge field.