Devices and methods for modifying an electromagnetic beam include a tunable refractive medium, an input waveguide configured for directing an incident radiation to the tunable refractive medium, and at least one output waveguide configured for directing a focused radiation emanating from the tunable refractive medium. The tunable refractive medium comprises first electrodes coupled to a first surface of a periodic dielectric medium, and second electrodes coupled to a second surface of the periodic dielectric medium. The periodic dielectric medium includes a dielectric periodicity configured for providing a negative refraction of the incident radiation and focusing the focused radiation at a focal location. The focal location may be modified by at least one electromagnetic signal applied between the first electrodes and the second electrodes.