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

A numerical investigation has been undertaken of the operating characterist ics of Terahertz Optical Asymmetric Demultiplexer (TOAD) devices subject to frequency-detuned signal and control picosecond optical pulses, taking int o account the wavelength dependence of the differential gain coefficient an d carrier density linewidth enhancement factor. It is shown that, by shifti ng 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 ene rgy demonstrates small changes over a broad frequency detuning range. The s imulations show excellent agreement with published experimental measurement s. Furthermore, two operational modes for the TOAD configuration are identi fied.