Circuit Elements for Optical Frequencies

Researchers at the University of Pennsylvania propose to shrink circuits in order to save space and power and, more importantly, to accommodate electronic applications at much higher frequencies than are possible with current models, applications that include nano-optics, optical information storage, and molecular signaling.

Electric circuit elements, among them resistors, capacitors, and inductors, come in a variety of sizes to deal with a variety of applications at a range of frequencies. The familiar electrical grid, for example, operates at a frequency of 60 Hz. A circuit designed to process radio signals operates at the 100-megahertz range. A typical frequency domain for computers is 1 GHz. Higher still, microwave applications often operate at the 10-GHz (10¹⁰ Hz) level.

Nader Engheta (engheta@ee.upenn.edu, 215-898-9777) and his Penn group would like to extend the circuit concepts up to optical frequencies, around 10¹⁵ Hz. To do this, instead of just shrinking the classic circuit elements to fraction of the typical wavelength of the optical signal being processed (around 500 nm), the Penn proposal is to make nano-inductors, nano-capacitors and nano-resistors out of sub-wavelength nano-particles, fashioned from appropriate materials on a substrate with lithographic techniques. Possible applications would include direct processing of optical signals with nano-antennas, nano-circuit-filters, nano-waveguides, nano-resonators, and even nano-scaled negative-index optical structures. (Engheta et al., Physical Review Letters, upcoming article; http://www.ee.upenn.edu/~engheta/)