Enhanced TOAD performance by negative frequency-detuned signal and control picosecond optical pulses

A numerical investigation has been undertaken of the operating characteristics of Terahertz Optical Asymmetric Demultiplexer (TOAD) devices subject to frequency-detuned signal and control picosecond optical pulses, taking into account the wavelength dependence of the differential gain coefficient and carrier density linewidth enhancement factor. It is shown that, by shifting the signal pulses toward lower frequencies compared with that of control pulses, the contrast ratio can be significantly enhanced and the amplitude modulation can simultaneously be considerably decreased. The switching energy demonstrates small changes over a broad frequency detuning range. The simulations show excellent agreement with published experimental measurements. Furthermore, two operational modes for the TOAD configuration are identified.