Ferroelectric liquid-crystal modulator with large switching rotation angle for polarization-independent binary phase modulation

Abstract

In this work a ferroelectric liquid crystal (FLC) modulator with a non-standard large switching rotation angle, close to 90 ◦, is fabricated and characterized. The modulator acts as a switchable wave-plate with an in-plane rotation of the principal axis under the action of a bipolar voltage. In the ideal situation of half-wave retardance, the device is shown to behave as a binary 𝜋 phase modulator independently of the input state of polarization. We provide physico-chemical properties of the liquid crystalline mixture used to fabricate the FLC modulator with such large switching angle. The characterization method of the device optical properties is presented, which allows the localization of the two LC stable states, the unambiguous determination of the rotation angle, and the evaluation of the spectral retardance function. We demonstrate the polarization-independent 𝜋 phase shift using an adapted Young’s type interferometer for real-time measurements, where we further analyze the operational frequency limits of the device. This FLC operational mode can be exploited to produce binary-phase polarization- independent diffractive optical elements.