Optical beam deflection by phase-controllable dual-period grating employing liquid crystal

A dual-period grating is proposed that can change the period and the phase difference in the grating structure, allowing the switchable diffraction allocation of transmitted light. Liquid crystal is assumed to be a variable-refractive-index medium confined in the grating grooves. The distribution of the transmitted diffraction efficiencies is analysed using a rigorous diffraction analysis for dual-period gratings and this reveals that the efficiencies can be maximized among the zeroth-, first-, and second-order waves successively according to the refractive index change in the liquid crystal. The analytical model provides insight into the operation of the device and emphasizes its potential application as an optical beam deflector with large deflection angles.