Science blog
Orbital mechanics affect methane levels
Antarctic lake keeps its secrets for now
How snakes lost their legs
Researchers ponder cancer origins
Forming social networks a no-brainer
'Niceness' partly genetic, say scientists
Omega-3 may keep blindness at bay
Coral shines light on rainfall records
Old bone proves Lucy was no swinger
Scientists unlock cosmic ice riddle
Study links pesticides to Parkinson's
Digital world growing faster every year
Energy drinks put kids at risk: report
Robotics speed up cancer drug development
Zinc cuts short the common cold
Counting kicks in at 18 months
NASA spacecraft unravels comet mystery
Astronomers dig up cannibalised galaxy
Study links extreme weather to climate change
Turkey quake gives warning clues
US scientists build first 'antilaser'
Website meltdown leaves scientists fuming
Earth 'unrecognisable' by 2050: experts
Canola fungus genome unravelled | На сайте: | Интересное здесь: | Секс комиксы на русском по материалам сайта.
Backward bending light key to stealth
Scientists have for the first time demonstrated a reversal of the optical Doppler effect, an advance that could lead to the development of 'invisibility cloak' technology.

The Doppler effect describes the change in frequency of waves whenever there is a relative movement between an observer and a wave's source.

Most people would know of it in relation to sound - for example, the change in pitch of a police siren as it nears and then passes. As it gets closer the sound frequency increases, and as it moves away the frequency decreases.

Light behaves in a similar way. When an object and an observer move closer together, light frequency increases from red wavelengths to blue.

When the light source moves further away, light frequency decreases from blue to red.

In a paper published today in the Nature Photonics journal, researchers from Swinburne University in Melbourne and their collaborators from the University of Shanghai for Science and Technology, have demonstrated the reversal of this effect, which does not occur naturally.

That is, when an object and a light wave detector moved closer together, they were able to decrease the light frequency from blue wavelengths to red ones, and vice versa.

"This is the first time that the inverse Doppler effect has been demonstrated in the optical region," says Professor Min Gu, Director of Swinburne's Centre for Micro-Photonics.
Concept realised after 45 years

Prior research in the United Kingdom showed the phenomenon was possible with microwaves. Although scientists had suspected since the 1960s that the reverse Doppler effect was possible with light waves, the technology didn't exist to prove the concept.

The researchers achieved this by creating an artificial nanostructured crystal - known as a 'photonic crystal' - out of silicon.

"In our super prism the dispersion of light was twice the magnitude of a standard Newton prism," Gu says.

"This large angle makes the prism's refractive index - a property that determines how fast light travels through it - change to negative."

All materials that occur in nature have a positive refractive index. This means whenever they move in respect to an observer, they will exhibit the standard Doppler effect.

"By creating this artificial material, with a negative refractive index, we were able to reverse this natural phenomenon," Gu says.

Swinburne University Senior Research Fellow Baohua Jia, a co-author on the paper, explains the phenomenon.

"For example if you have stick and you put that into water, what you expect to see is that the stick is bending towards you. If you have a negative index material the bend will be opposite," she says. "It's counterintuitive."

By projecting a laser beam onto the photonic crystal 'super prism' and changing the distance between it and the detector, the researchers were able to create an inverse Doppler effect phenomenon.
Invisibility cloaks

The researchers say that being able to reverse the Doppler effect is a promising sign for the future development of technology such as invisibility cloaks, which effectively bend light around an object. According to Professor Gu this technology, which US researchers have already demonstrated on a micro-scale, may be closer to becoming a reality than most people think.

The technology may see earlier deployment in optical telecommunications and medical imaging.

But Jia says at this stage it's just a demonstration of the fundamental physics.

"This paper is not really trying to emphasise the potential application, but rather to demonstrate that we can actually achieve it by using this artificial negative index material," she says.

"Although you know from principle it should be possible, when you really observe it it's very exciting."

Brain efficiency comes from parents
Backward bending light key to stealth
Signs of 'alien life' found in meteorites
Accurate blood test for Down's
Disaster volunteers at risk: study
Elephants smart as chimps, dolphins
Gadgets ruining people's sleep
Why skin doesn't dissolve in the bath
Astronomers find old heads in a young crowd
Paper leads to perfect beer head
Researchers locate brain's loudness map
Jamming may leave GPS in the wilderness
Pain washes guilt away
Quake could alter Tokyo risk: experts
Japan meltdown not like Chernobyl: expert
Dreamtime astronomers understood meteors
CERN restarts search for cosmic origins
Nuclear Contamination: What to Do
Bet-hedging 'key to natural selection'
Humans age same as other primates
US overdue, under-prepared for huge quake
Sperm's egg-seeking secrets revealed
Lasers to nudge space junk out harm's way
Researchers uncover gastro's sugary secret
Kepler probes inside swollen red giant
Randomness could 'improve democracy'
Moonageddon: Apocalypse not
Museum unveils Columbian mammoth
Ink-jet inspire scientists to make skin
Seaweed offers clues against malaria
Christchurch quakes may be connected
Solar storms pose risk to technology
Study finds fences thwart cane toad
Mobile phone alters brain activity
Sticky dots approved for clinical trial
Humans stink worse than other animals
Putting the bounce in carbon balls
Sulphur secrets uncovered
Cool laser makes atoms march in time
Hot flashes may be a sign of good heart
Scientists see the birth of a new planet
X-ray expectations change search methods
Eucalypt-harming fungus here to stay
Life elements came from outer space
Cricket wimps use perfume to find mates
Orphan planets could support life
Speech lights up visual cortex in blind
How the Sun loses its spots
Cancer resistance mechanism found
Fungus turns Amazonian ants into zombies
Tiny grains record solar system's infancy
Antarctic ice forming beneath glaciers
Visit Statistics