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World’s first ‘photon copier’ on a chip
A RESEARCH team at the University of California at Santa Barbara (UCSB) has for the first time incorporated on a single chip both a widely tunable laser and an all-optical wavelength converter, thereby creating an integrated photonic circuit for transcribing data from one color of light to another. Such a device is key to realizing an all-optical network. This research is being funded by a Defense Advanced Research Projects Agency (DARPA) Microsystems Technology Office (MTO) grant to push the boundary for photonic-circuit functional integration.
The new postage-stamp-size device is a tunable “photon copier,” which eliminates electronics as the middleman.
It is as if information on orange paper were being copied onto red paper. The information stays the same, but the colour of the paper on which it is conveyed is different. By that analogy the tunable laser supplies the red paper, and the wavelength converter functions as the copy-machine transcribing the information of the orange original to red. The tunable laser is able to supply a wide range of colours and hues to copy onto, and the wavelength converter is able to maintain or improve the quality of the image, a process called “regeneration.”
Daniel Blumenthal, leader of the research group and a UCSB professor of electrical and computer engineering, figures this successful demonstration of two capabilities on one photonic chip means more to come.
“People are now accustomed,” he said, “to think of a silicon substrate with a seemingly innumerable number of transistors on it. But that sophisticated electronic technology of today began back in the 1960s with a couple of transistors, and photonics is just beginning to enter that stage. We have been working long and hard at cracking this problem, and we are finally at the demonstration phase.”
UCSB graduate student Milan Masanovic presented the findings at the 15th annual meeting of the “Indium Phosphide and Related Materials Conference,” held in May in Santa Barbara.
A “tunable” laser enables the dialing up of different colours (that is, a single miniscule device can be programmed to emit at one frequency and then re-programmed to emit at another by electronically changing the effective optical length of its cavity and the shape of its internal colour filter).
The all-optical wavelength converter is an SOA-based Mach-Zehnder interferometer (SOA-MZI), which the paper’s authors note “also implements the significant feature of digital signal regeneration.” Digital regeneration is key to moving optical signals around a network with many nodes and long stretches of fiber in between and is a feature that electronics uses pervasively.
Astronomers count the stars
Astronomers in Australia say there are ten times more stars in the visible Universe than all the grains of sand on the world's beaches and deserts.
From the darkest parts of Earth, the naked human eye can see about 5,000 stars; from a brightly lit city street, only about 100.
But modern telescopes tell a different story.
The Australian astronomers used some of the world’s most powerful instruments to measure the brightness of all the galaxies in one sector of the cosmos — and then calculated how many stars they must have contained.
From that measurement, they proceeded to work out a figure for the whole of the visible Universe, which they believe is much more accurate than previous estimates.
That figure — presented to the International Astronomical Union conference in Sydney — is the kind that really can be called astronomical (no pun intended): 70 sextillion, or seven followed by 22 zeroes.
That is more than the total number of grains of sand in all the Earth’s beaches and deserts. But that is only the stars in the visible Universe within range of our telescopes.
Dr Simon Driver, of the Australian National University, says the actual total could be much, much bigger still — in fact, it could be infinite. He believes that many of the stars out there have planets, and some of those probably have life.
But they are so far away from Earth, he says, that we may never be able to contact anyone living on them.
New protein’s role in obesity
There is more to losing weight than diet and exercise, according to investigators the Research Institute at the McGill University Health Centre. Their study is the first to identify a new receptor protein present on fat cells that may play a role in fat metabolism. The findings, published recently in the Journal of Biological Chemistry, have implications for the many individuals suffering from obesity. “We have identified a receptor protein on fat cells that when stimulated may increase the amount of lipid stored in fat reservoirs,” says MUHC researcher Dr Katherine Cianflone. “This protein, C5L2, is made by fat tissue, is on the surface of fat cells and binds a specific hormone to increase fat production.”
Dr Cianflone, an associate professor at McGill University, with colleagues from McGill University and the UK characterized the binding activities of C5L2. They showed that this protein is a cell surface receptor that binds acylation stimulating protein (ASP), a protein known to affect fat production.
“People who are obese have high levels of ASP,” says Dr Cianflone. “One potential key to battling this condition is to disrupt the ASP-C5L2 complex. In the future, we may be able to slow down this fat-producing process by identifying molecules that will block C5L2 activity.” — Dawn ScienceDotcom report
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