Figueiredo, J. M. L.Ironside, C. N.Stanley, C. R.2012-06-052012-06-052002Figueiredo, J. M. L.; Ironside, C. N.; Stanley, C. R. Ultralow voltage resonant tunnelling diode electroabsorption modulator, Journal of Modern Optics, 49, 5-6, 939-945, 2002.0950-0340AUT: JLO01539;http://hdl.handle.net/10400.1/1191Embedding a double barrier resonant tunnelling diode (RTD) in a unipolar InGaAlAs optical waveguide gives rise to a very low driving voltage electroabsorption modulator (EAM) at optical wavelengths around 1550 nm. The presence of the RTD within the waveguide core introduces high non- linearity and negative di erential resistance in the current±voltage (I±V) characteristic of the waveguide. This makes the electric ®eld distribution across the waveguide core strongly dependent on the bias voltage: when the current decreases from the peak to the valley, there is an increase of the electric ®eld across the depleted core. The electric ®eld enhancement in the core-depleted layer causes the Franz±Keldysh absorption band-edge to red shift, which is responsible for the electroabsorption e ect. High-frequency ac signals as low as 100mV can induce electric ®eld high-speed switching, producing substantial light modulation (up to 15 dB) at photon energies slightly lower than the waveguide core band-gap energy. The key di erence between this device and conventional p-i-n EAMs is that the tunnelling characteristics of the RTD are employed to switch the electric ®eld across the core-depleted region; the RTD- EAM has in essence an integrated electronic ampli®er and, therefore, requires considerably less switching power.engResonant tunneling diodejournal article2012-05-11