Seth Fortuna
Department of Electrical Engineering and Computer Sciences, UC Berkeley
BSAC Graduate Researcher
Dissertation Presentation
May 2, 2017 | 12:00 to 01:00 | 540 Cory Hall
Host: Ming Wu
Traditional semiconductor light emitting diodes (LEDs) have low modulation speed because of long spontaneous emission lifetime. Spontaneous emission in semiconductors (and indeed most light emitters) is an inherently slow process owing to the size mismatch between the length of the atomic optical dipole oscillations responsible for light emission and the wavelength of the emitted light. More simply stated: semiconductors behave as a poor antenna for its own light emission. By coupling a semiconductor at the nanoscale to an external antenna, the spontaneous emission rate can be dramatically increased alluding to the exciting possibility of an antenna-LED that can be directly modulated faster than the laser. Such an antenna-LED is well-suited as a light source for on-chip optical communication where small size, fast speed, and high efficiency are needed to achieve the promised benefit of reduced power consumption of on-chip optical links compared with less efficient electrical links. Despite the promise of the antenna-LED, significant challenges remain to implement a practical antenna-coupled device in a monolithically integrated manner. Notably, most demonstrations of antenna-enhanced spontaneous emission have relied upon optical pumping of the light emitting material which is useful for fundamental studies; however, for a practical antenna-LED an electrical injection scheme is required. In this talk, I will report the demonstration of an electrically-injected III-V antenna-LED coupled to a cavity-backed slot antenna with a 200-fold increase in the spontaneous emission rate. The design principles, fabrication, and measurement of this electrically-injected antenna-LED will be discussed. I will show that 100 Gbps direct modulation rate at high efficiency is eventually possible with this antenna-LED device and is therefore suitable as a light source for on-chip optical interconnects.
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