InGaAs amplifier for loss-compensation in nanoplasmonic circuits

Abstract

Surface plasmon polaritons have become a contender for next-generation optical computing with their superior subwavelength modal confinement and nonlinearity over conventional photonics. Gap plasmon waveguides, also known as metal-insulator-metal (MIM) waveguides, have been shown to have one of the best balances in the inherent trade-off between confinement (<200nm) and propagation length (several microns) among plasmonic waveguide geometries. There is great interest in introducing gain into these plasmonic systems to compensate for their innate short propagation lengths. To this end, we present an electrically pumped Ag/HfO2/In0.485Ga0.515As/HfO2/Ag metal-insulatorsemiconductor-insulator-metal (MISIM) amplifier design for loss-compensation in nanoplasmonic interconnects at thetelecommunication wavelength of 1.55 μm. Finite difference time domain simulations utilizing the full rate equations were used to study the signal gain experienced upon transmission through the device. The direct bandgap semiconductorgain medium In0.485Ga0.515As was modeled as a four level laser system with homogeneous broadening. The effect of varying critical amplifier dimensions, namely the HfO2 spacer layer thickness and the width of the In0.485Ga0.515As core, on the amplifier’s performance was studied. A 3 μm long linear amplifier is shown to be capable of restoring a 500 GHz, 500 fs FWHM pulse train after 150 μm of propagation through a nanoplasmonic interconnect network without significant pulse distortion at a pump current density of 36.6 kA/cm2,or 1 mA total current. This pump current is shown to cause acceptable levels of device heating. A periodic arrangement of such devices could therefore be used to indefinitely increase the effective propagation length of a signal.