Metamaterials Transforming the Frequency of Optical Pulses

Transformation optics allows for the implementation of general relativistic effects inside optical systems. We present a time-dependent metamaterial device that mimicks the cosmological redshift. Theoretically, this linear medium requires a monotonically time-varying permittivity and permeability. Our recent results, however, indicate that it is possible to alter the frequency of optical pulses in a medium with solely a modulated permittivity. Furthermore, it is shown that the overall frequency shift does not depend on the actual variation of the permitivity or the inclusion of material losses. These robust features suggest a feasible technological implementation for frequency conversion of optical pulses.