  We present polarization-independent optical shutters with a sub-millisecond
switching time. The approach utilizes dual-frequency nematics doped with a
dichroic dye. Two nematic cells with orthogonal alignment are driven
simultaneously by a low-frequency or high-frequency electric field to switch
the shutter either into a transparent or a light-absorbing state. The switching
speed is accelerated via special short pulses of high amplitude voltage. The
approach can be used in a variety of electro-optical devices.
