High contrast, ultrafast optically addressed ultraviolet light modulator based upon optical anisotropy in ZnO films grown on R-plane sapphire

An optically addressed ultraviolet light modulator has been demonstrated which exploits the optical anisotropy in a ZnO film epitaxially grown on (011̄2) sapphire. This device achieves both high contrast and high speed by exploiting the anisotropic bleaching of the anisotropic absorption and concomitant ultrafast polarization rotation near the lowest exciton resonances produced by femtosecond ultraviolet pulses. The resultant modulation is characterized by a contrast ratio of 70:1, corresponding to a dynamic polarization rotation of 12°, and it decays to a quasiequilibrium value within 100 ps.