  In this paper, we present an electro-optical modulator made of two parallel
nanoelectromechanical silicon nitride string resonators. These strings are
covered with electrically connected gold electrodes and actuated either by
Lorentz or electrostatic forces. The in-plane string vibrations modulate
thewidth of the gap between the strings. The gold electrodes on both sides of
the gap act as a mobile mirror that modulate the laser light that is focused in
the middle of this gap. These electro-optical modulators can achieve an optical
modulation depth of almost 100% for a driving voltage lower than 1 mV at a
frequency of 314 kHz. The frequency range is determined by the string resonance
frequency, which can take values of the order of a few hundred kilohertz to
several megahertz. The strings are driven in the strongly nonlinear regime,
which allows a frequency tuning of several kilohertz without significant effect
on the optical modulation depth.
