The Electromagnetic Spectra of Ordinary Objects

Prof. Eli Yablonovitch Electrical Engineering and Computer Sciences Dept., University of California, Berkeley, CA, 94720, USA [email protected]

Abstract: There is an aspect of Electromagnetics that has been somewhat overlooked. Common everyday objects can act as electromagnetic resonators. Indeed ordinary objects have a series of resonant frequencies extending from radio waves up to optical frequencies. These resonant modes can be modeled as LC circuits. Thus every object that we encounter is an LC resonator. Since LC circuits support ac currents, and since ac currents imply electron acceleration, they inherently radiate into the far‐field. Therefore ordinary objects that we come across, in our daily lives, can act as electromagnetic antennas. This means that ordinary object have a Q‐ factor and a radiation Q‐factor for each resonant mode.

The lowest frequency resonance is especially characteristic of the object geometry, but there is an entire spectrum of higher frequencies to work with, a spectral fingerprint for everyday objects. Many of the properties that have been attributed to plasmonic resonances are actually universal, and they arise already in ordinary electromagnetics.

In communications technology, the antenna application is the most important. The antennas in cellphones, carried by almost everyone on the planet, are examples of multi‐frequency resonant objects, enabling wireless connectivity.

Biographical Sketch: Eli Yablonovitch is Director of the NSF Center for Energy Efficient Electronics Science (E3S), a multi‐University Center headquartered at Berkeley. Yablonovitch introduced the idea that strained semiconductor lasers could have superior performance due to reduced valence band (hole) effective mass. With almost every human interaction with the internet, optical occurs by strained semiconductor lasers. In his photovoltaic research, Yablonovitch introduced the 4(n squared) (“Yablonovitch Limit”) light‐trapping factor, in worldwide use for almost all commercial solar panels. Based on his mantra that “a great also needs to be a great LED”, the physics of high efficiency solar cells was permanently changed. This idea was implemented by his startup company Alta Devices Inc. Since 2011 every new world solar cell efficiency record, has been Alta breaking its own record, now reaching 29.1% at 1 sun. He is regarded as a Father of the Photonic BandGap concept, and he coined the term "". The geometrical structure of the first experimentally realized Photonic bandgap, is sometimes called “Yablonovite”. His company, Luxtera Inc., incorporates a photonic crystal in every silicon photonic chip, which provides optical communications within Data Centers, and serves billions of internet users every day. His startup company Ethertronics Inc., shipped over two billion cellphone antennas, reducing dropped calls for a significant fraction of humanity.He has been elected to the NAE, NAS, NAI, AmAcArS, and as Foreign Member, UK Royal Society. Among his honors is the OSA Ives/Quinn Medal, the Benjamin Franklin Medal, the IEEE Edison Medal, the Buckley Prize of the American Physical Society, and the Isaac Newton Medal of the UK Institute of Physics. 9