Fast analogue 2π phase modulation using a liquid crystal Pi-Cell

•The paper reports the development of a new liquid crystal (LC) optical phase modulator that can lead to full 2 π phase modulation combined with response times that are on the order of 1 ms.•Full 2 π phase modulation can be achieved at driving voltages that are readily accessible using existing silicon backplane technology.•The phase modulator is based on the fast-switching behaviour when operated in the symmetric H state of a nematic pi-cell.•Results are presented demonstrating the electric field conditions required to prolong the stability of the symmetric H state.•The experimental results are found to be in good agreement with results from simulations based upon Ericksen-Leslie continuum theory.