Departmental Seminar – Professor P.C. Ku

Ultracompact semiconductor light sources have revolutionized our life in many ways. They are enabling technologies for internet, optical data storage, and digital movie playback. Today, electrical engineers face new challenges such as continuing integrated circuit scaling, energy efficiency, renewable energy generation and electronic health care. In this talk, I will focus on how semiconductor light sources can continue to a play key role in these areas. In particular, I will discuss nanolasers for optical interconnect and RGB light-emitting diodes for energy efficient lighting.

Optical interconnect aims to use photons for signal routing within and between computer chips by offering the same advantages such as large signal bandwidth and low power consumption in an optical fiber communication (OFC) system. Indeed, most components except lasers in an OFC system have been scaled to nanometer dimensions to be compatible with integrated circuit devices. In the first half of the talk, challenges underlying the realization of a nanoscale laser (nanolaser) will be discussed. A current injection nanolaser structure will be proposed and analyzed. Initial experimental efforts will be described to demonstrate key physics toward the realization of a nanolaser structure for optical interconnect.

In the second half of the talk, we will discuss technological challenges underlying energy efficient lighting. Lighting constitutes 22% of electricity consumption. Yet most lighting devices we use today have efficiencies far less than 25%. Increasing lighting efficiency to 75% can reduce 20% of electricity consumption and 10% of CO2 emission. We will describe how nanostructured semipolar quantum wells can significantly enhance the efficiency of GaN LEDs. We will also discuss how to potentially integrate highly efficient RGB LEDs to achieve excellent color rendering index and color temperature for lighting.

P.-C. Ku received the B.S. degree from the National Taiwan University in 1995 and the Ph.D. degree from the University of California, Berkeley, in 2003, both in electrical engineering. During his PhD study, he was a recipient of the Berkeley Fellowship.

From 2003 to 2004, he was a postdoctoral researcher at the Center for Optoelectronic Nanostructured Semiconductor Technology in Berkeley, where his research focused on slow light and nano-optoelectronic materials. From 2004 to 2005, he was a senior process engineer with Intel Corporation where his research focused on the phase change memory. Since 2006, he has been an Assistant Professor in the Department of Electrical Engineering and Computer Science, University of Michigan Ann Arbor. His research interests include nanoscale optoelectronic devices and materials.

Dr. Ku is an honorary member of Phi-Tau-Phi and a member of the Optical Society of America. He received the Ross Tucker Memorial Award in 2004.