Simplified optimum phase-only configuration for a TNLCD

Abstract

We propose and implement simplifications to the optimum configuration of a twisted-nematic liquid-crystal display (TNLCD) operating as a phase modulator. As previously proposed, such an optimum configuration requires a generator of elliptic polarization, at the input, and a detector of elliptic polarization, at the output. Both the generator and the detector of elliptic polarization are formed by a quarter wave plate and a linear polarizer, appropriately arranged. As a first modification of the optimum phase configuration we removed the quarter-wave plate at the output of the TNLCD. The remaining components, two polarizers and a wave plate are arranged and oriented in such a way that the quality of phase modulation is very similar to that obtained with the arrange using two wave plates. This modification reduces complexity and cost of the mostly-phase setup arranged with the TNLCD. Our experimental implementation of the modified phase configuration employed a laser with a wavelength of 457 nm. As another modification of the setup, instead of a quarter-wave plate, optimized at 457 nm, we employed a half-wave plate optimized at 633 nm. The required elliptic state at the input of the TNLCD was generated by the appropriate arrangement of the linear polarizer and the wave plate.