The effect was first demonstrated in limited cases more than a decade ago, but by achieving it in novel ways, two groups “have made negative refraction a practical reality at optical frequencies,” said Sir John Pendry, a professor of physics at Imperial College London who was not involved in the new work.
Now, following recent breakthroughs, researchers are laying the groundwork for a “perfect lens” that can resolve sub-wavelength features in real time, as well as a suite of other optical instruments long thought impossible. These devices sidestep old optical limits by bending rays of light the “wrong” way — a phenomenon known as negative refraction.
In addition to biological imaging, perfect lenses could be used for single molecule biosensing, nanofabrication, light harvesting and (in theory) perfectly efficient solar panels, among other possibilities.
“The only prerequisite for realizing [a perfect lens] is negative refraction, which we have demonstrated,” said Hayk Harutyunyan, a postdoctoral researcher at Argonne National Laboratory in Argonne, Ill., and lead author of one of the new studies. “The rest is just technical problems that one has to solve.”
From air to silver, every medium has a “refractive index” relating the velocity of light in a vacuum to its velocity inside the medium. This number, plugged into a thousand-year-old formula known as Snell’s Law, gives the angle to which a beam of light bends when it enters the medium. When light passes from air into glass, for example, the refractive index increases from about 1 to 1.5, meaning that the light slows down and its angle steepens.
In 1967, the Russian scientist Victor Veselago wondered: What if that number, and therefore that angle, was negative? His minus sign completely transformed the equations of optics, yielding fantastic new solutions in which light pulled instead of pushed when striking a surface, and stretched when it would normally compress into a shockwave. Best of all, while regular curved lenses can only form images of objects located at the “focal point,” negative refraction is achieved with a flat lens that can form images of large regions of space.
But it all seemed like make-believe. To negatively refract light, a material must somehow send its waves rippling backward as its energy flows forward. “The reaction of the scientific community to this result was initially not positive,” said Veselago, now 84. “Many believed that the negative sign … in the formula was some ‘mathematical joke’ and cannot be realized physically.”
Veselago spent several years searching for materials with a negative refractive index. “However, all my attempts failed,” he said. The concept was forgotten.
Then, in 2000, a paper by Pendry in Physical Review Letters reignited interest in the idea. Pendry proved that negative refraction enables not only flat but also “perfect” lensing because negatively refracting materials can pick up and amplify the tiny wavelets that hug the fine-grained edges of objects. Ordinarily, this “near field” radiation decays within nanometers of an object and only the larger crests and troughs propagate outward. But when near field light hits a negatively refracting medium, the minus sign transforms its decay into growth, amplifying the signal. In a perfect lens, no information is lost.
“It’s a very beautiful process if you look at the mathematics of it,” Pendry said.
He also discovered a strategy for bringing the enticing possibilities to life. A material’s refractive index is calculated from its response to electric and magnetic fields. By embedding microscopic structures in a material that resonate with these fields in specially tailored ways, the material’s natural, atomic response to light, which always gives a positive refractive index, could be overridden. The first demonstration of negative refraction followed within months. A team led by David Smith, now a physicist and electrical and computer engineer at Duke University, created an artificial material, or “metamaterial,” consisting of a metal mesh imprinted with millimeter-wide geometric patterns. And as reported in a 2001 paper in the journal Science, by reversing electric and magnetic fields of specific strengths, the device negatively refracted 3-centimeter-long microwaves.
Metamaterials have spawned numerous practical applications, including “cloaking” devices that reduce electrical interference by bending radio waves around receivers, tunable satellite antennas that can access the Internet from anywhere, and vehicle collision avoidance systems. But the Smith team’s metamaterials could not be used to create lenses that negatively refract broadband visible light. They operate at a single wavelength tied to the dimensions of the material, rather than over a spectrum of colors. And their size could not be reduced enough to resonate within the visible 400- to 700-nanometer wavelength range. A new approach was needed.
“After many years of people staring at this problem of negative refraction, we’re finally getting people mastering the very, very difficult technology of making materials which have this property,” Pendry said.
In work that Pendry calls “a technological tour de force,” researchers at the National Institute of Standards and Technology in Gaithersburg, Md., have exploited the optical properties of objects called plasmonic waveguides to create a negatively refracting flat lens like the one Veselago envisioned 45 years ago. “Our goal was to achieve it in the most classical form, as close as possible to the original presentation back in the ’60s,” said Henri Lezec, principal investigator of the project.
For a range of ultraviolet wavelengths, the lens — made of a stack of silver and titanium dioxide layers — has a refractive index of -1, roughly equal and opposite to that of air. When light in this wavelength range bounces off an object and strikes the lens at any angle, interplay between oscillations of electrons in the two types of layers causes the light to bend back to the mirror-image angle as it moves through the stack, converging to form an image of the object on the far side. Because the lens is flat rather than curved like a conventional lens, there are “infinite axes and a continuum of focal planes,” Lezec explained. That means the device can create an image of everything in its vicinity simultaneously. So far, as detailed in the journal Nature in May, the team has created images of test objects such as rings and crosses, but “it could be a cell incorporating some flourophores,” Lezec said.
The device “allows unprecedented control of light,” he said, with immediate applications in 3-D photolithography (micro- or nano-scale printing with light), optical switching (turning light circuits on and off) and imaging. The researchers are also exploring strange physical effects that Veselago argued would be possible with a negatively refracting flat lens, including negative radiation pressure — pulling objects by shining light on them.
“Lezec actually sees this thing fly in space the wrong way; it flies towards light when you illuminate it,” Smith said. The scientists, who do not believe the object actually violates a fundamental principle of physics known as the conservation of momentum, are working on a new theory to make sense of this behavior.
Lezec’s flat lens currently dissipates too much energy to sufficiently amplify near field light and achieve super-resolution, but an almost loss-free approach to negative refraction proposed by Pendry in 2008 has also been demonstrated at optical frequencies for the first time. Harutyunyan, Ryan Beams of the University of Rochester and Lukas Novotny of ETH Zürich used a pair of high-powered laser beams to create a hologram on a flake of multilayer graphene, an extremely thin carbon crystal. Graphene is a highly “nonlinear” material, meaning it enhances the strange effects exhibited by very intense light. When a beam of light strikes the hologram, the nonlinearity causes a time-reversed replica of the beam to form on the far side of the graphene flake. This is effectively equivalent to the original beam negatively refracting as it crosses the graphene.
The results were reported in the July issue of Nature Physics. “There’s a lot of firsts in this,” Smith said. “It’s a beautiful experiment.”
The researchers say that, further optimized, the device could be used for super-resolution imaging of visible light, with some caveats. Smith thinks the laser beams used to generate the hologram could disturb a biological sample. Another challenge will be magnifying the sub-wavelength image so that ordinary cameras can pick up its fine details. This could be done, for example, by combining the graphene structure with a hyperlens, a newly developed negatively refracting lens that is curved.
Pendry, who recently began collaborating with experimentalists to build a perfect lens, believes the coveted object will be realized in the next five to 10 years. Several other scientists concur. Even negatively refracting, but not quite “perfect,” lenses will yield many practical applications, Pendry said. He compares negatively refracting devices to the laser. When its invention was first reported in 1960 “it was couched as a solution in search of a problem,” he said. “That is not the way you’d describe the laser today.”
Original story reprinted with permission from Quanta Magazine, an editorially independent division ofSimonsFoundation.org whose mission is to enhance public understanding of science by covering research developments and trends in mathematics and the physical and life sciences.
DEKALB COUNTY, Ga. —
Washiqur Rahman: Another secular blogger hacked to death in Bangladesh
- The 27-year-old Rahman falls victim to the same brazen act that killed Avijit Roy
- The deaths have emboldened the movement, an activist says
(CNN)When American writer Avijit Roy was hacked to death on a Dhaka, Bangladesh, street in full view of horrified onlookers, blogger Washiqur Rahman doubled down.
Fundamentalists were choking free thought in his secular nation, he wrote. But they couldn’t silence it.
His friends warned him to be careful, to watch what he posted online. But Rahman dismissed those concerns, saying his Facebook profile page didn’t even bear his picture. They don’t even know what I look like, he told them.
On Monday, the 27-year-old Rahman fell victim to the same brazen act that killed Roy, hacked to death by two men with knives and meat cleavers just outside his house as he headed to work at a travel agency.
He was so maimed — with wounds to his head, face and neck — that police identified him through the voter identification card he was carrying.
His death was the second time in five weeks that someone was killed in Dhaka for online posts critical of Islam — but they are hardly the only two who’ve paid a steep price.
In the last two years, several bloggers have died, either murdered or under mysterious circumstances.
“The despicable murder of Avijit Roy last month should have led authorities to step up protection measures for bloggers and others at risk. The killing of Washiqur Rahman today is another clear example of the Bangladeshi government’s utter failure to ensure the safety of those at risk,” said Abbas Faiz of Amnesty International.
“How many more bloggers will have to be attacked before action is taken?”
As shocking as Rahman’s death was, the reaction from some quarters was equally disturbing.
On his Facebook page (for which he picked a custom URL that translates to “unbeliever”), Rahman had posted a picture with the hashtag #IamAvijit.
After his death, someone left a comment, “Now you are.”
Another wrote, “I felt sorry when I first learned of your death. But then I saw what you wrote and I am not.”
On his page, Rahman reposted a cartoon depicting Prophet Mohammed from the French satire magazine Charlie Hebdo. He wished a happy birthday to author Taslima Nasreen, who was forced to flee Bangladesh due to death threats from fundamentalists. And he “liked” a picture of sausages wrapped in crescent rolls that someone had captioned, “Pigs in burqas.”
Posts threatening him were numerous.
“Get ready for the afterlife,” one person commented on one of his posts.
“See you in hell,” said another.
He used to write under the pseudonym “Stupid Man” on a blog but switched to posting on Facebook after 2011.
On Facebook, he is credited for a series, “Jaw-crushing answers to insulting comments of atheists.”
There, he posted questions that critics of Islam often raised and then answered them. But he paired the answers in such a way that they highlighted the contradiction within Islam.
For example, one question asked what proof was there that the Quran was the word of God. The answer, “Mohammed said in his own words that the Quran is the word of God. Since Mohammed is the messenger of Allah, his claims are true.”
He placed the question next to one that asked, “What is the proof that Mohammed was the messenger of Allah?”
The answer, “The Quran claims that Mohammed was the messenger of Allah. And since the Quran is God’s word, its claims must be true.”
Asif Mohiuddin, a blogger who himself was wounded by machete-wielding attackers in 2013 but survived, remembered Rahman as a great satirist.
“I named him the George Carlin of Bangladesh,” he told the International Humanist and Ethical Union. “He wanted with all his heart, a true secular country, where everyone can practice their freedom.”
The irony is that the people who killed Rahman weren’t even familiar with his writings; they were simply following orders, police said.
Of the three involved in the Monday morning attack, two were quickly caught by bystanders.
In confessions to police, the pair — both students at Islamic schools — said they didn’t know what a blog was, nor had they seen Rahman’s writing.
They said they were acting on orders from another person who told them killing Rahman was a religious duty, Police Commissioner Biplob Kumar Sarkar told reporters.
The third person is still to be apprehended.
That appears to be par for the course in the killings of bloggers in Bangladesh.
The only person arrested in the killing of Roy, the U.S. blogger, is Farabi Shafiur Rahman, who had called for his death in Facebook posts.
There has been no conviction in the January 2013 attack on Mohiuddin.
And no convictions in yet another case — the hacking death of blogger Ahmed Rajib Haider, also in 2013.
“The Bangladeshi government must urgently establish accountability in this murder case and others,” the Committee to Project Journalists said after Rahman’s death. “Otherwise the rest of the country’s bloggers, commentators and journalists covering sensitive topics remain at grave risk of being attacked as well.”
Bloggers, unlike political parties, aren’t an organized force — and that makes them an easy target for radicals, said Imran Sarker, who heads the Blogger and Online Activists Network in Bangladesh.
“They want peace, they talk of humanity. If you strike them with stones, they don’t strike back. They try to reach you with flowers,” he said. “So, if you want to sow fear and stifle progressive thought, they are easy to pick on.”
But the deaths — of Rahman, of Roy, of Haider — have emboldened the movement, rather than chill them into silence.
“No one is cowering in their homes because this is happening. Because this has been happening regularly for a long time,” he said. “We want to take the society forward. We know we have a lot left to accomplish.”
I believe that many things attributed to the supernatural, or ‘Unknown,’ are automatically given special powers and considerations by the less than educated, and those who try to pad their understandings with fluff, because the cold, hard truth is just too much for an evolved ape brain to handle. I believe in the strict science because I have observed the evidence and have seen the validation process first hand, therefore, I do not have to imagine the unprovable to explain that which I cannot comprehend, because I actually DO comprehend the thing of which I speak.
I shall attempt to use a personal reference in which to illustrate the facts and evidence regarding the situation to which I refer. I am speaking, of course, to decisions made by human brains which defy logic and reason, but demonstrate the chemical process that is actually in control of all aspects of human decision making. We are the sum of the chemicals in our brains and nothing will interfere with this, not even the notion of romantic love which is, as I have said, just a chemical reaction in the brain of an evolved ape.
The science of love
When do you know if you fancy someone? What does love do to your brain chemicals, and is falling in love just nature’s way to keep our species alive?
We call it love. It feels like love. But the most exhilarating of all human emotions is probably nature’s beautiful way of keeping the human species alive and reproducing.
With an irresistible cocktail of chemicals, our brain entices us to fall in love. We believe we’re choosing a partner. But we may merely be the happy victims of nature’s lovely plan.
It’s not what you say…
Psychologists have shown it takes between 90 seconds and 4 minutes to decide if you fancy someone.
Research has shown this has little to do with what is said, rather
55% is through body language
38% is the tone and speed of their voice
Only 7% is through what they say
The 3 stages of love
Helen Fisher of Rutgers University in the States has proposed 3 stages of love – lust, attraction and attachment. Each stage might be driven by different hormones and chemicals.
Stage 1: Lust
This is the first stage of love and is driven by the sex hormones testosterone and oestrogen – in both men and women.
Stage 2: Attraction
This is the amazing time when you are truly love-struck and can think of little else. Scientists think that three main neurotransmitters are involved in this stage; adrenaline, dopamine and serotonin.
The initial stages of falling for someone activates your stress response, increasing your blood levels of adrenalin and cortisol. This has the charming effect that when you unexpectedly bump into your new love, you start to sweat, your heart races and your mouth goes dry.
Helen Fisher asked newly ‘love struck’ couples to have their brains examined and discovered they have high levels of the neurotransmitter dopamine. This chemical stimulates ‘desire and reward’ by triggering an intense rush of pleasure. It has the same effect on the brain as taking cocaine!
Fisher suggests “couples often show the signs of surging dopamine: increased energy, less need for sleep or food, focused attention and exquisite delight in smallest details of this novel relationship” .
And finally, serotonin. One of love’s most important chemicals that may explain why when you’re falling in love, your new lover keeps popping into your thoughts.
Does love change the way you think?
A landmark experiment in Pisa, Italy showed that early love (the attraction phase) really changes the way you think.
Dr Donatella Marazziti, a psychiatrist at the University of Pisa advertised for twenty couples who’d been madly in love for less than six months. She wanted to see if the brain mechanisms that cause you to constantly think about your lover, were related to the brain mechanisms of Obsessive-Compulsive Disorder.
By analysing blood samples from the lovers, Dr Marazitti discovered that serotonin levels of new lovers were equivalent to the low serotonin levels of Obsessive-Compulsive Disorder patients.
Love needs to be blind
Newly smitten lovers often idealise their partner, magnifying their virtues and explaining away their flaws says Ellen Berscheid, a leading researcher on the psychology of love.
New couples also exalt the relationship itself. “It’s very common to think they have a relationship that’s closer and more special than anyone else’s”. Psychologists think we need this rose-tinted view. It makes us want to stay together to enter the next stage of love – attachment.
Stage 3: Attachment
Attachment is the bond that keeps couples together long enough for them to have and raise children. Scientists think there might be two major hormones involved in this feeling of attachment; oxytocin and vasopressin.
Oxytocin – The cuddle hormone
Oxytocin is a powerful hormone released by men and women during orgasm.
It probably deepens the feelings of attachment and makes couples feel much closer to one another after they have had sex. The theory goes that the more sex a couple has, the deeper their bond becomes.
Oxytocin also seems to help cement the strong bond between mum and baby and is released during childbirth. It is also responsible for a mum’s breast automatically releasing milk at the mere sight or sound of her young baby.
Diane Witt, assistant professor of psychology from New York has showed that if you block the natural release of oxytocin in sheep and rats, they reject their own young.
Conversely, injecting oxytocin into female rats who’ve never had sex, caused them to fawn over another female’s young, nuzzling the pups and protecting them as if they were their own.
Vasopressin is another important hormone in the long-term commitment stage and is released after sex.
Vasopressin (also called anti-diuretic hormone) works with your kidneys to control thirst. Its potential role in long-term relationships was discovered when scientists looked at the prairie vole.
Prairie voles indulge in far more sex than is strictly necessary for the purposes of reproduction. They also – like humans – form fairly stable pair-bonds.
When male prairie voles were given a drug that suppresses the effect of vasopressin, the bond with their partner deteriorated immediately as they lost their devotion and failed to protect their partner from new suitors.
And finally … how to fall in love
Find a complete stranger.
Reveal to each other intimate details about your lives for half an hour.
Then, stare deeply into each other’s eyes without talking for four minutes.
York psychologist, Professor Arthur Arun, has been studying why people fall in love.
He asked his subjects to carry out the above 3 steps and found that many of his couples felt deeply attracted after the 34 minute experiment. Two of his subjects later got married.
These and other studies are factual and in to prove the chemical reaction that is LOVE. It is nothing more and it is only those who use pseudoscience that try to make chemicals more than they actually are. We skeptics are sure, I just will never show this post to a potential sex partner due to the inability of HER to face the scientific fact of the nature of romantic love.