原创 A look into optical rectifying antenna

Solar-based energy is often associated with electricity-generating solar cells; solar-based heating systems using a working fluid; solid-state thermoelectric-based conversion; or perhaps a solar-concentrator which liquefies some salt-based compound for storage .
 
Now there's a new entrant in the photon-to-electron race: an optical rectifying antenna, or rectenna. This highly experimental device, discussed here, was developed at the Georgia Institute of Technology (better known as "Georgia Tech"). It captures and rectifies photons to produce electricity directly; they claim this the first time this has been done. You can read a more-detailed technical discussion in this academic paper in Nature, as well.

Rectennas are not new: they have been used for forty-plus years in highly specialized situations to direct RF-to-electron conversion (and Google "Nikola Tesla" for even earlier efforts). Another recent story "Rectenna Serves 2.45-GHz Wireless Power Transmission" gives full details on one version which claims 63% conversion efficiency; certainly impressive. Looking at the RF article and all the details, you see that as in so many advanced ideas, the concept is straightforward but the actual implementation is quite complicated with many subtleties.

Similarly, reading the Georgia Tech paper in Nature, you get a good sense of the technical challenges of capturing and converting photons. The low efficiency of around 1% is certainly not marketable yet, as conventional solar cells are running in the 10-20% range, but you never know where these things will go, what breakthroughs may occur, or when they may happen (please, let's NOT see a roadmap yet, that's way too premature).

 
One other point is apparent looking at the optical rectenna: it is made possible due to advances in nanomaterials. I recently attended the annual conference of the Materials Research Society, where 5,000+ attendees discussed, explored, and demonstrated the latest in materials along with their creation, applications, and test at temperatures from near 0 K to thousands of degrees; the test aspect, even at room temperature, is a major challenge for many of these nanomaterials.

There's certainly lots of fascinating things happening that may have a significant impact on technology in ways we can't foresee yet. When we casually use packaged devices and products, it’s easy to not realize how much basic materials science are the now-routine enablers, in terms of new materials, ultrapure elemental and created materials, and understanding of their electrical, chemical, physical, optical, and mechanical properties.

Even if you see little need to follow developments in material science (we can't do everything), it's probably a good idea to at least follow developments in optical-related science, engineering, and test. Laser Focus World and Photonics (both available online and in print) are valuable and readable resources with insight, ideas, and even inspiration. Given the major role that optical concepts and components have in so many electronics systems, including LEDs, lasers, photodetectors, optical fiber links, filters, displays, and instrumentation, it's a worthwhile use of precious time.