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Topics: Research News

‘We’ve all been taught that this doesn’t happen’

By Nicole Casal Moore
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A dramatic and surprising magnetic effect of light discovered by University of Michigan researchers could lead to solar power without traditional semiconductor-based solar cells.

William Fisher, a doctoral student in applied physics, performing research on laser-induced magnetism.

William Fisher, a doctoral student in applied physics, performing research on laser-induced magnetism.

The researchers found a way to make an “optical battery,” said Stephen Rand, a professor in the departments of Electrical Engineering and Computer Science, Physics and Applied Physics.In the process, they overturned a century-old tenet of physics.”You could stare at the equations of motion all day and you will not see this possibility. We’ve all been taught that this doesn’t happen,” said Rand, an author of a paper on the work published in the Journal of Applied Physics. “It’s a very odd interaction. That’s why it’s been overlooked for more than 100 years.”Light has electric and magnetic components. Until now, scientists thought the effects of the magnetic field were so weak that they could be ignored. Rand and his colleagues found that at the right intensity, when light is traveling through a material that does not conduct electricity, the light field can generate magnetic effects that are 100 million times stronger than previously expected. Under these circumstances, the magnetic effects develop strength equivalent to a strong electric effect.”This could lead to a new kind of solar cell without semiconductors and without absorption to produce charge separation,” Rand said. “In solar cells, the light goes into a material, gets absorbed and creates heat. Here, we expect to have a very low heat load. Instead of the light being absorbed, energy is stored in the magnetic moment. Intense magnetization can be induced by intense light and then it is ultimately capable of providing a capacitive power source.”What makes this possible is a previously undetected brand of “optical rectification,” says William Fisher, a doctoral student in applied physics. In traditional optical rectification, light’s electric field causes a charge separation, or a pulling apart of the positive and negative charges in a material. This sets up a voltage, similar to that in a battery. This electric effect had previously been detected only in crystalline materials that possessed a certain symmetry.Rand and Fisher found that under the right circumstances and in other types of materials, the light’s magnetic field can also create optical rectification.”It turns out that the magnetic field starts curving the electrons into a C-shape and they move forward a little each time,” Fisher said. “That C-shape of charge motion generates both an electric dipole and a magnetic dipole. If we can set up many of these in a row in a long fiber, we can make a huge voltage and by extracting that voltage, we can use it as a power source.”The light must be shone through a material that does not conduct electricity, such as glass. And it must be focused to an intensity of 10 million watts per square centimeter. Sunlight isn’t this intense on its own, but new materials are being sought that would work at lower intensities, Fisher said.”In our most recent paper, we show that incoherent light like sunlight is theoretically almost as effective in producing charge separation as laser light is,” Fisher said.This new technique could make solar power cheaper, the researchers say. They predict that with improved materials they could achieve 10 percent efficiency in converting solar power to useable energy. That’s equivalent to today’s commercial-grade solar cells.”To manufacture modern solar cells, you have to do extensive semiconductor processing,” Fisher said. “All we would need are lenses to focus the light and a fiber to guide it. Glass works for both. It’s already made in bulk, and it doesn’t require as much processing. Transparent ceramics might be even better.”In experiments this summer, the researchers will work on harnessing this power with laser light, and then with sunlight.The paper is titled “Optically-induced charge separation and terahertz emission in unbiased dielectrics.” The university is pursuing patent protection for the intellectual property.

Nicole Casal Moore

Nicole Casal Moore

NICOLE CASAL MOORE spent five years as a newspaper reporter covering natural resources, agriculture and environment, as well as state and county governments in California and Virginia. She worked as an online magazine editor and public affairs manager at the National Conference of State Legislatures in Denver for five years. She has been a science writer and public relations representative at Michigan News and the U-M College of Engineering since 2007. Follow her on Twitter: @UMengineering and @UMncmoore.

COMMENTS

  • Colleen habrecht - 1977

    Keep it up! I was told yrs ago that the oil co’s forced all of the solar panel patents out of the scientists hands (at threat of life) & then made them too inefficient to be worth using. Was my friend correct?

    Reply

  • siang kwok

    Very interesting and timely discovery for green technology. How effective is the glass fiber discharging the high voltage (electrical resistance and wear and tear) for solar cell applications?

    Reply

  • Geoffrey Landis - 1980

    [sunlight] “must be focused to an intensity of 10 million watts per square centimeter” [to make this work as a solar energy converter].

    That’s a concentration ratio of a hundred million! The theoretical maximum is 140,000, and the record for highest solar concentration ever achieved is 84,000. They’re suggesting they could convert sunlight into electricity if they could “only” achieve a concentration ratio more than a thousand times higher than what’s ever been done?

    (reference to maximum concentration is from _Solar Electricity_ by T. Markvart, page 237. )

    Reply

  • David Marlow

    I remember reading recently of another discovery at another university of how light helps organise water mocules enhancing surface tension, into what they called a liquid crystal and they also feel that this could replace existing solar cells. Could these discoveries be related?

    Reply

  • Kenneth Schepler - 1975

    I hope those glasses Mr Fisher is wearing in the photo are laser safety glasses. The article has obviously been simplified for the masses. Go to the original article for a discussion of what has actually been demonstrated. J. Appl. Phys. 109, 064903 (2011); doi:10.1063/1.3561505 (8 pages)

    Reply

  • Ralph Dratman - 1972

    This article is very interesting, but I’m frustrated because I can’t tell what they found out.

    The crux seems to be “the magnetic field starts curving the electrons into a C-shape and they move forward a little each time. That C-shape of charge motion generates both an electric dipole and a magnetic dipole.”

    The magnetic field is curving the electrons into a C shape? Huh?

    Reply

  • bob 41 - 2007

    Great work guys!

    Reply

  • Mary Turzillo - 1970

    @Geoffrey Landis

    You must have missed the next sentence. No worries, I’ve pasted it below.

    “Sunlight isn’t this intense on its own, but new materials are being sought that would work at lower intensities, Fisher said.”

    Reply

  • Skippy James

    @Schepler, and I hope is shirt is 100% cotton, wtf!

    Reply

  • fred nerk - never

    There is light at the end of the tunnel after all,very well done guys and girls and best wishes from Ulladulla(Australia)

    Reply

  • Nico Staub

    This is AWESOME!

    Scientific revolutionaries…

    Biggest of my respects to the team.

    Reply

  • David McCutcheon - 1979

    This is not that surprising to me. I developed a theory of matter called ultrawave theory that treats light as converted electrons made from two different wave types. The electric and magnetic portions just happen to be in a ratio that is controlled by the speed of the waves. There is no reason that the two forces cannot be switched when traveling thru particular types of media. Actually, the most efficient light to electricity conversion would be a simple material that does the conversion from photon to electron with little additional processes.

    Reply

  • terry O'Malley - 4

    In your discription the requirment of light is a critical function in the success of this process; I am assumming, unless you stored the capacitance, the process would only generate usable energy during daylight hours-not counting the reduction of electrons in reflective light in cloud cover conditions. I think any improvement in efficency is required if this format of creating usable energy is to become a embedded process.

    Reply

  • carlos lacayo - 1992

    I wonder if they have tried using quartz shaped into symmetrical shapes will be more effective then glass. Or maybe even diamonds.

    Reply

  • Mystery Guest - 1975

    @carlos lacayo – Search for an old Wired article entitled “The New Diamond Age”. Synthetic diamond might be interesting/useful in this particular context.

    Reply

  • Harry Flotser - 1969

    Rectification of non-coherent, white-light!!
    Interesting! Wonder what the IIR loss is through the non-conducting medium?

    Reply

  • FELIX Jr. SAN BUENAVENTURA - 1978

    DATE: 10-MAY-2012

    INDEED, THIS IS AN AMAZING DISCOVERY BY YOUR TEAM OF PROF. STEPHEN RAND. IF THIS METHOD CAN BE PROVED EXPERIMENTALLY AND BECOMES SUCCESSFULL, THIS WILL USHER INTO A NEW METHOD OF MAGNETOOPTIC EFFECT OF LIGHT AND COMPARED WITH THAT OF CONVENTIONAL PHOTOELECTRIC EFFECT BY ALBERT EINSTEIN’S DISCOVERY AND IT WILL RIVAL THAT OF NIKOLA TESLA’S METHOD OF WIRELESS POWER TRANSFER AND TO HAVE FREE ENERGY FOR MANKIND.

    BY FELIX M.S.Jr.

    Reply

  • Cave Johnson - 1956

    They say great science is built on the shoulders of giants – not here. At Aperture we do all our science from scratch; no hand holding.

    Reply

  • Dave Mayton

    Students pay big money to attend U of M and they do the research and experiments. Yet the university gets the benefit of the patent?

    Reply

  • phil francis - left school at 16, so 40.

    The Rills go uphill and down hill and so could not be caused by water. Instead they carry all the hallmarks of being caused by massive thunderbolt discharges. With the amount of evidence continuing piling in from deep space and with what has now been collated (mainly by the scientists connected to the ‘Thunderbolts Project’),once looked at and only in minimal detail, an Electric Universe is being rationally realised as fact. (youtube) /watch?v=5DEvb6yEQ_0&list=PLwOAYhBuU3UeYFyfm2LilZldjJd48t6IY

    Reply

  • Kevin McCall

    This should be transferred over to space exploration? just a thought if you can use light for energy wouldn’t every solar system have a gas station?

    Reply

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