A waveguide based variable attenuator device including one or more attenuators each including a porous dielectric material; and a metal coating on the top of the dielectric material; and an actuator coupled to the attenuator. The actuator is configured to position, with nanometer resolution, the one or more attenuators in a waveguide configured and dimensioned to guide an electromagnetic wave having a frequency in a range of 100 gigahertz (GHz) to 1 terahertz (THz). The actuator controls at least one of a position or a volume of the one attenuator inserted in the waveguide to achieve a variable or pre-determined attenuation of the electromagnetic wave transmitted through waveguide.