Perfect lens could reverse Casimir force

Post new topic   Reply to topic    Institute of Nanotechnology Forum Index -> Nanooptics
View previous topic :: View next topic  
Author Message
Site Admin

Joined: 16 Mar 2004
Posts: 1392

PostPosted: Wed Apr 02, 2008 2:56 pm    Post subject: Perfect lens could reverse Casimir force Reply with quote

30 July 2007 Physics Web

Belle Dumé

The normally attractive Casimir force between two surfaces can be made repulsive if a "perfect" lens with a negative index of refraction is sandwiched between the surfaces, according to calculations done by physicists in the UK. Ulf Leonhardt and Thomas Philbin of the University of St Andrews reckon that the repulsive force may even be strong enough to levitate a tiny mirror. The repulsive effect - which has yet to be observed experimentally - could also help minimize the friction in micrometre-sized machines caused by the Casimir force. (New Journal of Physics to be published).

The mysterious attraction between two neutral, conducting surfaces in a vacuum was first described in 1948 by Henrik Casimir and cannot be explained by classical physics. Instead it is a purely quantum effect involving the zero-point oscillations of the electromagnetic field surrounding the surfaces. These fluctuations exert a "radiation pressure" on the surfaces and the overall force is weaker in the gap between the surfaces than elsewhere, drawing the surfaces together. Tiny though it is, the Casimir effect becomes significant at distances of micrometres or less and actually causes parts in nano- and micro-electromechanical systems (NEMS and MEMS) to stick together.

Now, Leonhardt and Philbin have calculated that the Casimir force between two conducting plates can turn from being attractive to repulsive if a "perfect" lens is sandwiched between them. A perfect lens can focus an image with a resolution that is not restricted by the wavelength of light. Such a lens could be made from a metamaterial made of artificial structures that are engineered to have negative index of refraction - which means that the metamaterial bends light in the opposite direction to an ordinary material.

According to the researchers, the negative-index metamaterial is able to modify the zero-point oscillations in the gap between the surfaces, reversing the direction of the Casimir force. Indeed, the researchers believe that this repulsive force is strong enough to levitate an aluminium mirror that is 500nm thick, causing it to hover above a perfect lens placed over a conducting plate.

Since the Casimir force acts on the length scale of nanomachines, manipulating it could be important for future applications of nanotechnology. "In the nano-world, the Casimir force is the ultimate cause of friction," Leonhardt told PhysicsWeb. "Our result means we could now envision frictionless machines or novel micromotors."

While physicists have had some success creating perfect lenses from negative-index metamaterials, the technology is still in its infancy. "The work points towards new applications of left-handed materials that are not strictly optical," says Federico Capasso of Harvard University, who studies the effect of the Casimir force on MEMS. "However, the materials are not easy to make so the concept may take a few years to realise."


Story posted: 30th July 2007
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    Institute of Nanotechnology Forum Index -> Nanooptics All times are GMT
Page 1 of 1

Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum

Powered by phpBB © 2001, 2002 phpBB Group