A study of the temporal response of a biased Fabry–Perot etalon with a nematic liquid crystal exposed to short (∼10 &mgr;s) voltage pulses is presented. It is found that the finesse is the crucial factor determining the achievable switching time. For a given maximum transmission the reflectivities of the Fabry–Perot mirrors are optimized to achieve minimum switching times. In particular, switching times of 0.5 &mgr;s with an initial transmission of 3% and a maximum value of 70% have been obtained. The experimental results are in good agreement with theory. ©1996 American Institute of Physics.