Carbon nanotubes for hybrid silicon photonics

Demanding applications such as video streaming, social networking, or web search relay on a large network of data centres, interconnected through optical links. The ever-growing data rates and power consumption inside these... [ view full abstract ]

Demanding applications such as video streaming, social networking, or web search relay on a large network of data centres, interconnected through optical links. The ever-growing data rates and power consumption inside these data centres are pushing copper links close to their fundamental limits. Optical interconnects are being extensively investigated, aiming to solve these limitations. Silicon photonics, due to its compatibility with the Si platform, has become one of the preferred solutions for the development of the future generation photonic interconnects. However, the current strategy for on-chip integration of all photonic and optoelectronic building blocks (sources, modulators and detectors…) relies on very different materials. For instance, Ge for detection, doped Si for modulators and III-V for lasing. This multi-material approach results in a complex fabrication process that offsets the cost-effectiveness of using silicon photonics.
Carbon nanotubes (CNTs) are being considered for the realization of next generation nanoelectronic systems, due to their exceptional transport capabilities, chemical stability and potential CMOS compatibility. On the other hand, CNTs are nanomaterials that exhibit very interesting properties for the photonics field. Specifically, they show strong room-temperature photo-luminescence and electro- luminescence in the near-infrared wavelength range, Stark effect, Kerr effect and absorption. Hence, they are considered a particularly promising alternative solution for the implementation of optoelectronic functionalities in silicon photonics, including light generation, modulation and detection.
Here, we report on the development of new integration schemes to couple the light emission from CNTs into optical resonators implemented on the silicon-on-insulator platforms. We obviated unwanted absorption effects resulting in a substantial improvement of the resonant light enhancement. We have optimized and experimentally validated different resonant structures, including ring resonators, microdisks, 1D photonic crystal cavities and 2D slot photonic crystal cavities as an effective means of on-chip resonant enhancement of CNTs emission. At the same time, this integration approach allowed coupling the generated photoluminescence from CNTs to integrated Si photonic waveguides with enhanced signal to noise ratios.