Various embodiments of the present invention are directed to external, electronically controllable, negative index material-based modulators. In one aspect, an external modulator comprises a negative index material in electronic communication with an electronic signal source. The negative index material receives an electronic signal encoding data from the electronic signal source and an unmodulated carrier wave from an electromagnetic radiation source. Magnitude variations in the electronic signal produce corresponding effective refractive index changes in the negative index material encoding the data in the amplitude and/or phase of the carrier wave to produce an electromagnetic signal.