  In this paper we report on a low energy consumption CMOS-compatible plasmonic
modulator based on Franz-Keldysh effect in germanium on silicon. We performed
integrated electro-optical simulations in order to optimize the main
characteristics of the modulator. A 3.3 $dB$ extinction ratio for a 30 ${\mu}m$
long modulator is demonstrated under 3 $V$ bias voltage at an operation
wavelength of 1647 $nm$. The estimated energy consumption is as low as 20
$fJ/bit$.
