(Press-News.org) MADISON – Electrical engineers at The University of Texas at Arlington and at the University of Wisconsin-Madison have devised a new laser for on-chip optical connections that could give computers a huge boost in speed and energy efficiency.
The team published its findings on July 22, 2012 in Nature Photonics.
At just 2 micrometers in height – smaller than the width of a human hair – the surface-emitting laser's vastly lower profile could make it cheaper and easier for manufacturers to integrate high-speed optical data connections into the microprocessors powering the next generation of computers.
Traditionally, edge-emitter lasers are considered as the candidate for on-chip optical links. But since mirrors are hard to form in such lasers and because the lasers occupy a large chip area, researchers have been challenged to find a practical way to monolithically integrate the mirrors on silicon chips.
Surface-emitting lasers necessary for a high-speed optical links between computer cores could be 20 to 30 micrometers tall, slightly bigger than one hole in the mesh of a car's oil filter. Yet the research team's engineers say that on a 1.5-micrometer wavelength optically connected chip, lasers of that size dwarf their silicon surroundings.
"It sits tall on the chip, like a tower," says Zhenqiang Ma, a UW-Madison professor of electrical and computer engineering. "That is definitely not acceptable."
Weidong Zhou, a UT Arlington professor of electrical engineering, says one challenge was integrating light into silicon chips, as silicon itself is not an efficient light emitter.
Zhou and Ma have collaborated to shrink on-chip lasers in recent years with funding from the U.S. Air Force Office of Scientific Research, Army Research Office and Defense Advanced Research Projects Agency.
As a solution, the researchers propose replacing layers and layers of reflectors necessary in the traditional distributed Bragg reflector laser design with two highly reflective photonic crystal mirrors.
Composed of compound semiconductor quantum well materials, each mirror is held in place with silicon nanomembranes, extremely thin layers of a silicon.
Zhou says integrating compound semiconductor quantum wells with silicon is a promising approach. "We apply a nanomembrane transfer printing process to accomplish this goal," he says.
One layer of photonic crystal is equal to about 15 to 30 layers of dielectric reflectors found in conventional lasers.
As a result, manufacturers could fabricate 2-micrometer-high lasers for data links with performance that could equal current designs.
In addition to their larger size, reflectors for conventional lasers are made of materials grown only at very high temperatures, which means they can damage the chip they are placed upon during production. Since fabrication via transfer printing can occur at much lower temperatures, Zhou and Ma hope their laser design can be used to place optical links on silicon chips with much less wasted material, time and effort.
Optical data links already exist at the largest scales of data networks – the Internet's backbone is composed mainly of fiber-optic links between countries, cities and houses. But currently, that data moves over to slower metal connections and wiring as it travels from a regional hub to your house, your computer and eventually between the CPU cores within of the processor powering your machine.
"In the future, you'll see a move to optical at each step," Ma says. "The last step is within the chip, module to module optical links on the chip itself."
Through Semerane Inc., the Texas-based startup Zhou and Ma founded, the two hope to implement their production process in functional on-chip photonic crystal membrane lasers that could eventually be part of the next generation high-speed computer processors.
"We believe this laser will be used to make data links more practically available," Ma says.
"It is truly an interdisciplinary team effort," Zhou says. "The co-existence of photonics with electronics on the chip level shall enable multi-functional energy-efficient super-chips for applications in computing, communications, sensing, imaging and so on."
With widespread adoption of processors that use their laser design for optical links, Ma and Zhou could have a hand in increasing the speed along the local leg of the information superhighway.
"Eventually, a CPU core in America could be connected to another CPU core in Asia, with optical connections all along the chain," Ma says.
### Read the full paper here: http://dx.doi.org/
—Mark Riechers, mriechers@engr.wisc.edu, 608-265-8592
—Herb Booth, hbooth@uta.edu, 817-272-7075
Printed photonic crystal mirrors shrink on-chip lasers down to size
2012-07-24
ELSE PRESS RELEASES FROM THIS DATE:
Study offers new clue on how brain processes visual information
2012-07-24
WINSTON-SALEM, N.C. – July 23, 2012 – Ever wonder how the human brain, which is constantly bombarded with millions of pieces of visual information, can filter out what's unimportant and focus on what's most useful?
The process is known as selective attention and scientists have long debated how it works. But now, researchers at Wake Forest Baptist Medical Center have discovered an important clue. Evidence from an animal study, published in the July 22 online edition of the journal Nature Neuroscience, shows that the prefrontal cortex is involved in a previously unknown ...
Herding sheep really are selfish
2012-07-24
VIDEO:
Many animals spend time together in large groups not because they enjoy each other's company, but rather because it lowers their own chances of being eaten should an uninvited guest...
Click here for more information.
Many animals spend time together in large groups not because they enjoy each other's company, but rather because it lowers their own chances of being eaten should an uninvited guest arrive on the scene—or so the theory goes. Now, researchers who have ...
Sex is the ultimate risky business (for flies in bat territory, that is)
2012-07-24
VIDEO:
This shows Natterer's bat catching a pair of copulating flies (black circle) from the cowshed ceiling and a Natterer's bat attacking an ultrasonic loudspeaker that plays fly copulation buzzes in...
Click here for more information.
If you are a fly living with bats in a cowshed, sex really could be the death of you. That's according to a study in the July 24th issue of Current Biology, a Cell Press publication, showing that bats eavesdrop on the sounds of fly sex ...
Functional neurologic abnormalities due to prenatal alcohol exposure are common
2012-07-24
Alcoholism: Clinical & Experimental Research
Functional neurologic abnormalities due to prenatal alcohol exposure are common
A new study has examined heavy alcohol exposure during pregnancy using population-based data in Chile.
Approximately 80 percent of the children examined had one or more abnormalities associated with alcohol exposure.
Functional neurologic impairment was the most frequent and sometimes only sign of alcohol exposure.
Most children who are exposed to large amounts of alcohol while in the womb do not go on to develop fetal alcohol syndrome ...
When campuses and their surrounding communities can join forces to stop alcohol abuse
2012-07-24
Contact: Marguerite Beck
marbeck@wakehealth.edu
336-716-2415
Wake Forest School of Medicine
Ralph Hingson, Sc.D., M.P.H.
rhingson@mail.nih.gov
301-443-1274
National Institute on Alcohol Abuse and Alcoholism (NIAAA)
Alcoholism: Clinical & Experimental Research
When campuses and their surrounding communities can join forces to stop alcohol abuse
U.S. college students typically drink more than their non-college peers and are slow to 'mature out' of their harmful drinking patterns.
A new study examines a combined community-level and campus-level approach ...
Disinhibition/drinking differences between African-American and European-American youth
2012-07-24
Alcoholism: Clinical & Experimental Research
Disinhibition/drinking differences between African-American and European-American youth
African American adolescents drink less than European American adolescents.
A new study examines racial differences in disinhibition.
Results indicate that European American youth have higher levels of sensation seeking while African American youth have higher levels of impulsivity.
Compared to European American adolescents, African American adolescents are more likely to abstain from alcohol, drink less frequently, and engage in ...
Alcoholism and HIV infection have different effects on visuomotor procedural memory processes
2012-07-24
Alcoholism: Clinical & Experimental Research
Alcoholism and HIV infection have different effects on visuomotor procedural memory processes
Visuomotor procedural memory processes include driving a car, riding a bike, and using a computer mouse.
This study examined the separate and combined injurious effects of chronic alcoholism and HIV infection upon visuomotor procedural memory processes.
Results indicate the two conditions differently affect the processes involved in procedural learning and memory of visuomotor information.
The different effects on memory processes ...
Loss of tiny liver molecule might lead to liver cancer
2012-07-24
Liver cancer is the third leading cancer killer worldwide and new treatments are urgently needed.
This study shows that loss of a regulatory molecule called microRNA-122 leads to liver cancer.
The findings suggest that developing a drug that restores microRNA-122 levels might offer a new way to treat this deadly disease.
COLUMBUS, Ohio – A new study shows that loss of a small RNA molecule in liver cells might cause liver cancer and that restoring the molecule might slow tumor growth and offer a new way to treat the disease.
The animal study was led by researchers ...
First results of community health campaign in Uganda for HIV and other diseases
2012-07-24
A clinical study in a remote region of southwest Uganda has demonstrated the feasibility of using a health campaign to rapidly test a community for HIV and simultaneously offer prevention and diagnosis for a variety of other diseases in rural and resource-poor settings of sub-Saharan Africa.
At the XIX International AIDS Conference in Washington, D.C., the first results of this study, called the "Sustainable East Africa Research in Community Health (SEARCH) Collaboration," will be described by doctors at the University of California, San Francisco (UCSF), San Francisco ...
UCSF/SFGH researchers call for change in new FDA recommendation on HIV and TB drug doses
2012-07-24
In January, 2012, the U.S. Food and Drug Administration (FDA) issued new guidelines on dosing of an HIV medication used to treat people infected with both HIV and tuberculosis (TB) because of a potential interaction between two of the main drugs used to treat each disease.
The drug rifampin, used for treating TB, can lower levels of the HIV medicine efavirenz, so the FDA recommended that patients who weigh more than 50 kg (110 pounds) and who are taking both medications should get 30 percent larger doses of efavirenz (an increase from 600 mg to 800 mg).
Now, a new ...