Polarisation-free and high-resolution holographic grating recording and optical phase conjugation with azo-dye doped blue-phase liquid crystals

We present the results of a detailed study of the mechanism and dynamics of holographic Bragg grating formation in azo-dye doped blue-phase liquid crystals. The principal mechanism leading to refractive index modulation is lattice distortion caused by photo-activated trans–cis isomerism of the azo-dye dopant. High diffraction efficiency bulk (Bragg) gratings with grating spacing as small as 1 μm can be written with low optical power and do not require specific optical field polarisation. Furthermore, the written grating can be prolonged by uniform illumination with another laser, instead of being erased. Azo-doped blue-phase liquid crystals thus present themselves as highly promising photosensitive materials for high-resolution holographic recording and image processing application. An experimental demonstration of holographic image reconstruction via optical phase conjugation with excellent aberration correction capability is presented.