EE PhD Oral Examination: Dany-Sebastien Ly-Gagnon, Tuesday, March 1st, 9:45am

Stanford University PhD Dissertation Defense - Department of Electrical Engineering

Integrated plasmonic waveguide photodetectors for optical interconnection of silicon chips

Speaker: Dany-Sebastien Ly-Gagnon
Research Advisor: Professor David A.B. Miller
Date: Tuesday, 1 March 2011
Time: 9:45 a.m. (Refreshments at 9:30 a.m.)
Location: Nano Building, Room 232

ABSTRACT

To keep pace with the scaling of semiconductor technology, the amount of energy required to transmit one bit of information needs to be drastically reduced. Optical interconnects may become a key technology in enabling high bandwidth interconnections, provided that its components operate at sufficiently low energies per bit. At the receiver, the capacitance of the photodetector limits the speed and power consumption that can be achieved. Lower capacitance can be achieved by reducing the physical size of the photodetector to nanoscale volumes, an order of magnitude smaller than the optical wavelength. Metallic nanostructures can be used to bridge this size mismatch between the optical mode and the optoelectronic device, enhancing interaction between the optical signal and the photodetector. Plasmonic waveguides provide an efficient way of routing optical signals with deep subwavelength mode dimensions and integrate well with nanoscale photodetectors, providing a route towards highly integrated low capacitance detectors for optical interconnects.

In this talk, I will present our work on integrated plasmonic waveguide photodetectors. We developed a model based on the modal characteristic impedance that allows us to calculate transmission and reflection in deep subwavelength metal slot waveguides. We illustrate how this approach can be used to design an asymmetric Fabry-Perot photodetector with high efficiency despite metallic losses. We experimentally demonstrate propagation of highly confined optical modes at near-infrared wavelength in two-conductor plasmonic waveguides and its detection with an on-chip integrated photodetector. Our results show that these optical modes can propagate several optical wavelengths and make it through 90 degree bends, while the strong optical confinement allows the signal to be detected in photodetectors with limited footprint.