Enhanced Frequency Shift in Optical Slow-Wave Structures

Doppler effects in electrooptic media can be exploited to induce a continuous, accurate and fast shift of the carrier frequency of optical signals, without the need for nonlinear materials, additional optical sources or high optical power levels. In this contribution, it is shown that the efficiency of the frequency-shift process can be significantly enhanced by slow-wave propagation in coupled resonator optical structures. By means of time- domain numerical simulations, lumped and traveling wave architectures for slow-wave frequency converters are discussed and compared to the state-of-the-art devices, with the aim of clarifying the role played by optical resonators. Relationships between the maximum frequency shift and the bandwidth of the dynamic slow-wave structure are derived. Stop light effects are also explored, showing that the speed of the frequency-shift process can be arbitrarily slowed down, if the optical pulse is trapped, frequency shifted while inside the structure and finally released.