<\/a><\/p>\n\nThis effect dovetailed with another of graphene\u2019s exceptional characteristics: Electrons pass through it at very high speeds, up to a million meters per second, or about 1\/300 the speed of light in a vacuum. That meant that the two speeds were similar enough that significant interactions might occur between the two kinds of particles, if the material could be tuned to get the velocities to match.<\/p>\n
That combination of properties \u2014 slowing down light and allowing electrons to move very fast \u2014 is \u201cone of the unusual properties of graphene,\u201d says Solja\u010di\u0107. That suggested the possibility of using graphene to produce the opposite effect: to produce light instead of trapping it. \u201cOur theoretical work shows that this can lead to a new way of generating light,\u201d he says.<\/p>\n
Specifically, he explains, \u201cThis conversion is made possible because the electronic speed can approach the light speed in graphene, breaking the \u2018light barrier.\u2019\u201d Just as breaking the sound barrier generates a shockwave of sound, he says, \u201cIn the case of graphene, this leads to the emission of a shockwave of light, trapped in two dimensions.\u201d<\/p>\n
The phenomenon the team has harnessed is called the \u010cerenkov effect, first described 80 years ago by Soviet physicist Pavel \u010cerenkov. Usually associated with astronomical phenomenon and harnessed as a way of detecting ultrafast cosmic particles as they hurtle through the universe, and also to detect particles resulting from high-energy collisions in particle accelerators, the effect had not been considered relevant to Earthbound technology because it only works when objects are moving close to the speed of light. But the slowing of light inside a graphene sheet provided the opportunity to harness this effect in a practical form, the researchers say.<\/p>\n
There are many different ways of converting electricity into light \u2014 from the heated tungsten filaments that Thomas Edison perfected more than a century ago, to fluorescent tubes, to the light-emitting diodes (LEDs) that power many display screens and are gaining favor for household lighting. But this new plasmon-based approach might eventually be part of more efficient, more compact, faster, and more tunable alternatives for certain applications, the researchers say.<\/p>\n
Perhaps most significantly, this is a way of efficiently and controllably generating plasmons on a scale that is compatible with current microchip technology. Such graphene-based systems could potentially be key on-chip components for the creation of new, light-based circuits, which are considered a major new direction in the evolution of computing technology toward ever-smaller and more efficient devices.<\/p>\n
\u201cIf you want to do all sorts of signal processing problems on a chip, you want to have a very fast signal, and also to be able to work on very small scales,\u201d Kaminer says. Computer chips have already reduced the scale of electronics to the points that the technology is bumping into some fundamental physical limits, so \u201cyou need to go into a different regime of electromagnetism,\u201d he says. Using light instead of flowing electrons as the basis for moving and storing data has the potential to push the operating speeds \u201csix orders of magnitude higher than what is used in electronics,\u201d Kaminer says \u2014 in other words, in principle up to a million times faster.<\/p>\n
One problem faced by researchers trying to develop optically based chips, he says, is that while electricity can be easily confined within wires, light tends to spread out. Inside a layer of graphene, however, under the right conditions, the beams are very well confined.<\/p>\n
\u201cThere\u2019s a lot of excitement about graphene,\u201d says Solja\u010di\u0107, \u201cbecause it could be easily integrated with other electronics\u201d enabling its potential use as an on-chip light source. So far, the work is theoretical, he says, so the next step will be to create working versions of the system to prove the concept. \u201cI have confidence that it should be doable within one to two years,\u201d he says. The next step would then be to optimize the system for the greatest efficiency.
\nThis finding \u201cis a truly innovative concept that has the potential to be the key toward solving the long-standing problem of achieving highly efficient and ultrafast electrical-to-optical signal conversion at the nanoscale,\u201d says Jorge Bravo-Abad, an assistant professor at the Autonomous University of Madrid, in Spain, who was not involved in this work.<\/p>\n
In addition, Bravo-Abad says, \u201cthe novel instance of \u010cerenkov emission discovered by the authors of this work opens up whole new prospects for the study of the \u010cerenkov effect in nanoscale systems, without the need of sophisticated experimental set-ups. I look forward to seeing the significant impact and implications that these findings will surely have at the interface between physics and nanotechnology.\u201d<\/p>\n
Abstract<\/b><\/p>\r\n
<\/div>\r\n
<\/div><\/div>\n
Graphene plasmons have been found to be an exciting plasmonic platform, thanks to their high field confinement and low phase velocity, motivating contemporary research to revisit established concepts in light\u2013matter interaction. In a conceptual breakthrough over 80 years old, \u010cerenkov showed how charged particles emit shockwaves of light when moving faster than the phase velocity of light in a medium. To modern eyes, the \u010cerenkov effect offers a direct and ultrafast energy conversion scheme from charge particles to photons. The requirement for relativistic particles, however, makes \u010cerenkov emission inaccessible to most nanoscale electronic and photonic devices. Here we show that graphene plasmons provide the means to overcome this limitation through their low phase velocity and high field confinement. The interaction between the charge carriers flowing inside graphene and the plasmons enables a highly efficient two-dimensional \u010cerenkov emission, giving a versatile, tunable and ultrafast conversion mechanism from electrical signal to plasmonic excitation.<\/p>\n
SOURCES – MIT news, Nature Communication<\/p>\n","protected":false},"excerpt":{"rendered":"
When an airplane begins to move faster than the speed of sound, it creates a shockwave that produces a well-known \u201cboom\u201d of sound. Now, researchers at MIT and elsewhere have discovered a similar process in a sheet of graphene, in which a flow of electric current can, under certain circumstances, exceed the speed of slowed-down … <\/p>\n
Read more<\/a><\/p>\n","protected":false},"author":2,"featured_media":29096,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[68,14,462,76,532,5,269],"_links":{"self":[{"href":"https:\/\/www.nextbigfuture.com\/wp-json\/wp\/v2\/posts\/2136"}],"collection":[{"href":"https:\/\/www.nextbigfuture.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.nextbigfuture.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.nextbigfuture.com\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.nextbigfuture.com\/wp-json\/wp\/v2\/comments?post=2136"}],"version-history":[{"count":0,"href":"https:\/\/www.nextbigfuture.com\/wp-json\/wp\/v2\/posts\/2136\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.nextbigfuture.com\/wp-json\/wp\/v2\/media\/29096"}],"wp:attachment":[{"href":"https:\/\/www.nextbigfuture.com\/wp-json\/wp\/v2\/media?parent=2136"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.nextbigfuture.com\/wp-json\/wp\/v2\/categories?post=2136"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.nextbigfuture.com\/wp-json\/wp\/v2\/tags?post=2136"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}