  We demonstrate an electrically controlled metal-VO2 metasurface for the
mid-wave infrared that simultaneously functions as a tunable optical switch, an
optical limiter with a tunable limiting threshold, and a nonlinear optical
isolator with a tunable operating range. The tunability is achieved via Joule
heating through the metal comprising the metasurface, resulting in an
integrated optoelectronic device. As an optical switch, the device has an
experimental transmission ratio of ~100 when varying the bias current.
Operating as an optical limiter, we demonstrated tunability of the limiting
threshold from 20 mW to 180 mW of incident laser power. Similar degrees of
tunability are also achieved for nonlinear optical isolation, which enables
asymmetric (nonreciprocal) transmission.
