Optical modulation at around 1550 nm in a InGaAlAs optical waveguide   containing a InGaAs/AlAs resonant tunnelling diode
  We report electro-absorption modulation of light at around 1550 nm in a unipolar InGaAlAs optical waveguide containing a InGaAs/AlAs double-barrier resonant tunneling diode (DB-RTD). The RTD peak-to-valley transition increases the electric field across the waveguide, which shifts the core material absorption band-edge to longer wavelengths via the Franz-Keldysh effect, thus changing the light-guiding characteristics of the waveguide. Low-frequency characterisation of a device shows modulation up to 28 dB at 1565 nm. When dc biased close to the negative differential conductance (NDC) region, the RTD optical waveguide behaves as an electro-absorption modulator integrated with a wide bandwidth electrical amplifier, offering a potential advantage over conventional pn modulators. 
J.M.L. Figueiredo, A.R. Boyd, C.R. Stanley, C.N. Ironside, S.G.   McMeekin, and A.M.P. Leite