Abstract
Nanoscale light sources using metal cavities have been proposed to enable high integration density, efficient operation at low energy per bit and ultra-fast modulation, which would make them attractive for future low-power optical interconnects. For this application, such devices are required to be efficient, waveguide-coupled and integrated on a silicon substrate. We demonstrate a metal-cavity light-emitting diode coupled to a waveguide on silicon. The cavity consists of a metal-coated III–V semiconductor nanopillar which funnels a large fraction of spontaneous emission into the fundamental mode of an InP waveguide bonded to a silicon wafer showing full compatibility with membrane-on-Si photonic integration platforms. The device was characterized through a grating coupler and shows on-chip external quantum efficiency in the 10−4–10−2 range at tens of microamp current injection levels, which greatly exceeds the performance of any waveguide-coupled nanoscale light source integrated on silicon in this current range. Furthermore, direct modulation experiments reveal sub-nanosecond electro-optical response with the potential for multi gigabit per second modulation speeds.
Highlights
Nanoscale light sources using metal cavities have been proposed to enable high integration density, efficient operation at low energy per bit and ultra-fast modulation, which would make them attractive for future low-power optical interconnects
An light-emitting diodes (LEDs)-based nanophotonic source allows for a modulation speed beyond the 3 dB bandwidth without a substantial decrease in modulation depth as compared with lasers whose response deteriorates quickly beyond this point and large extinction ratios at high speeds can be maintained in nano-LEDs at low bias current levels, unlike a laser which requires high pumping conditions to reach large bandwidths
We conceived the device in a III–V membrane on silicon (IMOS) approach[25], which has been shown to enable a variety of functionalities including lasers[26], metal grating couplers[27], polarization converters[28] and demultiplexers[29], but we note that a similar approach could be implemented for coupling a InGaAs nanopillar to a silicon photonic waveguide[5], as proposed theoretically[21]
Summary
Nanoscale light sources using metal cavities have been proposed to enable high integration density, efficient operation at low energy per bit and ultra-fast modulation, which would make them attractive for future low-power optical interconnects For this application, such devices are required to be efficient, waveguide-coupled and integrated on a silicon substrate. Simple theoretical considerations show that aggressive scaling of metallic lasers well below the wavelength ( in the plasmonic regime) will result in unacceptably high threshold current densities[15] In this context, the use of nanoscale light-emitting diodes (LEDs) instead of lasers for on-chip communication systems requiring low power consumption has been suggested[15], and submicrometer LEDs have been demonstrated[16,17,18,19]. The reported data together with numerical simulations show the potential of metal-cavity nanopillar LEDs for efficient low-power interconnects operating at Gb/s data rates
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