EE PhD Oral Examination - Kevin C.Y. Huang, Friday May 4, 10am CISX-AUD

University PhD Dissertation Defense

Electrically driven optical antennas and slot waveguides: towards an on-chip subwavelength light source

 

Kevin Chih-Yao Huang

Department of Electrical Engineering

Advisor: Prof. Mark L. Brongersma

 

Friday May 4^th 2012

10:00 am

(Refreshments at 9:45 am)

 

Location: Paul G. Allen Auditorium (CIS-X 101)

http://cis.stanford.edu/directions/

 

Abstract: 

The most recent developments in on-chip molecular sensing and high-speed optical interconnection set stringent limits on the power consumption, operating speed, and physical footprint of the constituent active devices. In order to achieve new performance targets, it becomes particularly important to scale down optical sources to the nanoscale. This effort is inhibited by the fundamental diffraction limit of light, where the size reduction of photonic elements dramatically increases optical losses, thereby reducing the interaction strength of optoelectronic processes.

Metallic nanostructures which supports coupled electron and electromagnetic wave oscillations called surface plasmon polaritons (SPPs) facilitate stronger light-matter interaction at the nanoscale as they are capable of concentrating and confining light to deep subwavelength volumes. These plasmonic structures enable significant modification of the electromagnetic environment, allowing nearby optical emission processes to be enhanced and controlled. In my presentation, I discuss two examples that combine a semiconductor quantum well (QW) with metallic nanostructures to realize nano-light-emitting diodes (LEDs) with tailored emission properties.

In the first example, I illustrate the design methodology and demonstrate experimentally, compact antenna-electrodes which facilitate simultaneous operation as elec­trodes for current injection into nanoscale-LED and as antennas capable of optically manipulating the electroluminescence. Differ­ent designs of the antenna electrode dimensions show dipolar, quadrupolar and higher order radiation patterns with enhanced directivity and polarization ratio which are in good agreement with full-field numerical simulations.

In the second example, I demonstrate the integration of a metal-clad nano-LED with metal-dielectric-metal slot waveguides to realize the smallest electrically driven two-dimensionally confined guided optical mode to date. The routing, splitting, free space coupling and directional coupling of the slot waveguide mode are characterized to enable future optical nano-circuits for high speed optical interconnects and sensing in nanoscale volumes.