Linear Pulse Compansion based on Space-Time Modulation

We presents a new approach for pulse compansion, i.e., compression or expansion, based on copropagating spacetime modulation. An engineered asymmetric space-time modulated medium copropagating with a pulse compands the pulse continuously as it propagates. The space-time medium locally modifies the velocity of different sections of the pulse in order to modify its shape as it copropagates with the pulse. The proposed compansion scheme is linear with respect to the input wave and therefore it can be used to compand multiple pulses simultaneously. Moreover, it does not distort the pulse during compansion. Finally, it can also be used for frequency up- or down-conversion of modulated electromagnetic pulses.