High-Speed Operation Of The Heterostructure Field-Effect Optical Modulator

The Heterostructure Field Effect Optical Modulator (HFEOM) is a waveguide modulator that operates via band filling of quantum wells using charge transfer from an adjacent n+ charge sheet. The control of this charge transfer is with a gate electrode as in a field effect transistor. The band filling of the quantum wells produces a blue-shift of the absorption edge that is used to modulate the incident light. This device is compatible in both growth and processing with the associated in- plane laser and field effect transistor. The initial high speed results of HFEOMs in the InGaAs/GaAs material system are presented using a double quantum well active region. This structure has demonstrated a 35:1 extinction ratio for a 2 volt swing (-1 V to +1 V) on a 300 micrometers long device along with excellent wavelength compatibility with a 400 micrometers in-plane laser fabricated from the same wafer. Capacitance limited modulation bandwidths of 1.2 GHz and 1.6 GHz are measured for 5 micrometers and 2 micrometers rib widths respectively.