Electrically controlled dynamic holographic gratings in fullerene C60-doped nematic liquid crystals

Abstract

A new method to demonstrate the dynamic enhancement of the photorefractive effect in C60-doped homeotropically aligned 4-cyano-4′-pentyl-biphenyl (5CB) liquid crystals under the influence of an externally applied dc voltage is presented in the read-out process. We observed clear holographic images due to the transient diffraction efficiency enhancement controlled by the application of a dc voltage. The hidden gratings are due to a light-induced surface-charge modulation and amplified by the Carr–Helfrich effect in the presence of the electric field produced by the dc voltage. A qualitative analysis of the phenomenon, according to which the effective bulk voltage is modulated due to light-induced surface modifications, is proposed. We achieved the highest transient first-order diffraction efficiency of up to 40%. The effective nonlinear index coefficient is as large as 0.2 cm2 W−1.