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Microscopic Antennas for Light Beat Fiber Optics

Optical signals use light not only for telecommunications, but for sensors that can detect even scant amounts of toxins. Most optical signals are routed down fibers like a conduit, but now Rice University researchers are proposing to use microscopic optical antennas to receive light in the same way a cell phone's antenna receives radio waves.

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Microscopic Antennas for Light Beat Fiber Optics
Electromagnetic radiation runs the gamut from long-wavelength radio waves to short-wavelength light waves, but antennas are usually thought of as useful only for radio waves. Since an antenna's size is related to the wavelength it is intended to receive, radio antennas must be a millimeter or longer. Since light's wavelength is measured in nanometers, antennas scaled down to that size should be able to receive the nanometer wavelengths of light.

Now, Rice University researchers have proven this concept by crafting optical antennas at nanometer wavelengths, permitting the microscopic antennas to receive light waves the same way that cell phone antennas receive radio waves.

An artist's rendering of how plasmons in a pair of gold sub-nanometer electrodes concentrate light from a laser (source: Natelson Lab/Rice University).

Cell phone antennas work by providing propagating electromagnetic waves with a physical "sounding board," allowing them to lock onto the signal to receive it. The metallic structure of the antenna, when resonating with the incoming electromagnetic waves, produces an oscillating voltage for the cell phone�s radio frequency (RF) front-end circuitry.

For the microwave frequencies used by cell phones, that wavelength is measured in millimeters and corresponds to the length of the phone's internal antenna.

Next: Mimicking Radio-Wave Antennas >>