2015 Isaac Newton medal of the Institute of Physics

Professor Eli Yablonovitch, University of California, Berkeley, for his visionary and foundational contributions to photonic nanostructures.

Professor Eli Yablonovitch

Eli Yablonovitch is a scientist with a profound understanding of fundamental physical and engineering principles in photonics and a keen interest in translating these concepts into practical applications that address real societal issues. A key theme throughout his work has been the problem of solar cell efficiency, which he first started working on in the early 1980s, then with the Exxon Research Centre. He introduced the 4n2 factor that describes the light-trapping phenomenon applied in all high-performance solar cells, and that is still widely referenced in research papers on light trapping today. His 4n2 factor is now also referred to as the “Yablonovitch Limit”.

He developed the “photonic bandgap” concept, motivated by the desire to suppress spontaneous emission in photonic devices. The idea is to make materials with photonic bandgaps in which electromagnetic waves cannot propagate at certain frequencies. Inside a photonic bandgap, optical modes, spontaneous emission and zero-point fluctuations are all absent. Spontaneous emission is a fundamental phenomenon associated with all devices that emit light. It can often be troublesome, limiting the performance of these devices in applications such as illumination, displays, optical communication, solar energy and quantum information systems.

The ingenious idea of photonic bandgaps brought together concepts from solid state physics and photonics and it eventually spawned the entirely new research field now known as photonic crystals. Photonic crystals have caused a true paradigm-shift in photonics, based on their ability to control the flow of light to an extent that was hitherto unthinkable. As a result, photonic crystals are now being used in research areas as diverse as quantum computation, nanoscale imaging and sensing, photovoltaics, optical interconnects, and high performance light-emitting diodes.

Yablonovitch also introduced the idea that strained semiconductor lasers could have superior performance due to reduced valence band (hole) effective mass. Almost all semiconductor lasers use this concept, for optical telecommunications, in most computer mice, for DVD players and in the ubiquitous red laser pointers. With almost every human interaction with the internet, optical telecommunication occurs by strained semiconductor lasers.