Transmission and reflection phase gratings formed in azo-dye-doped chiral nematic liquid crystals

Transmission and reflection gratings were simultaneously formed in azo-dye-doped chiral nematic liquid crystals ((NLCs)-L-*) with planar alignment. The formation process is based on a phototuning of the Bragg reflection band of the (NLC)-L-*. The helical pitch of the photoreactive (NLC)-L-* was spatially controlled with intensity variation of interference light. The resultant periodic structure showed both transmissive and reflective diffractions due to the spatially modulated light intensities. The observed dependence of diffraction efficiencies on the polarization states of the probe beam was well explained by considering a spatial modulation of the helical pitch.