Innovative silicon wafer technology serves as game-changer for high speed connections at data centers

The immense growth of data centers powering the internet cloud has brought with it a demand to move large quantities of data faster and farther. Newly developed silicon wafer technology with tiny black holes, developed by UC Davis electrical engineers, acts a photodetector to move massive amounts of data worldwide at a cheaper cost.

Saif Islam of the UC Davis Department of Electrical and Computer Engineering collaborated with the Silicon Valley startup company W&W Sens Devices Inc., to develop this technology. The research was recently published in the online journal, Nature Photonics.

“Big data is what everyone talks about these days,” said Yang Gao, a postdoctoral scholar in Islam’s group. “The need for faster optical communication and the demand for higher bandwidth cloud computing are growing exponentially.”

The eminent  “cloud,” is a metaphor for the internet. Cloud computing means storing and accessing information and programs over the internet instead of on a computer hard drive.

The main application of new silicon wafer technology is for data centers. A central issue of optics for data communication in the centers is the expensive cost for the data transfer rate, which is currently about $10 per gigabit per second.

“We believe this technology will help to further reduce the cost to single digit dollar per Gb/s,” said postdoctoral scholar Hilal Cansizoglu of the UC Davis Integrated Nanodevices and Nanosystems Lab.

The most striking feature of this new technology is the pattern of tiny black holes tapered in the silicon, only about 1 micrometer in size.

These holes essentially trap photons, which are tiny quantized particles of light, and divert them sideways which allows for high-speed data connections.

“A large number of simulations, experimental attempts and combined approaches helped us narrow-down our design window [for the optimal pattern of tapered holes],” Islam said.

After two long years of experimentation, the researchers concluded on a pattern of holes that taper toward the bottom of the wafer.

Traditionally, silicon is not considered a good material for a photodetector to use in data communication applications because very thick layers are needed to absorb light efficiently. Thick layers prevent the detector from having a fast speed and therefore produce a low data transmission. However, the new silicon wafer technology simultaneously has features of high data collection efficiency and high data transmission rate.

“Our designs use very thin silicon layers with photon-trapping holes, and the light coming into the photodetector is bent sideways so that it can be absorbed efficiently,” Gao said. “At the same time, the thin active region results in the data conversion rate of 25 gigabits per second and higher.”

Currently, when computer engineers want to move large quantities of data at a fast rate, the use of fiber-optic cables are employed. These cables transmit the data as pulses of light, and at the receiving end of the transmission is a detector that converts these signals to electronic pulses.

Unfortunately, in order to capture the all the data and be efficient as possible, the downside is a slow rate. In these situations, materials such as gallium arsenide can be used to increase speed and efficiency about, 10 times more, but it is significantly more expensive.

“This new [silicon wafer] technology [with tapered holes] and many others can make the optical communication more affordable, more efficient and ultimately improves the user experience that benefits everyone,” Gao said.

The ability for electrical engineers at UC Davis to collaborate with other engineers and scientists both within the UC system and other laboratories has contributed to the success of an experimental photodetector and solar cell using the new technology.

“UC Davis is luckily backed by a wide spectrum of available microfabrication tools and facilities both at Davis and in UC system,” Gao said. “We have access to several of national leading nanofabrication research facilities including Center of Nano-MicroManufacturing (CNM2) at UC Davis, and Marvell Nanofabrication Laboratory at UC Berkeley.”

High speed connections are increasingly vital at data centers, and the silicon wafer technology can be a game changer for how data is transmitted.

“The publication of this technological breakthrough has the potential to spark new design ideas and impact academic and industrial research toward the development of higher efficiency photodetectors,” Gao said.
Written by: Shivani Kamal — science@theaggie.org

UC Davis Environmental Health Science Center hosts collaboration event to examine water safety, toxicity in Central Valley

The first ever UC Davis Environmental Health Science (EHS) Academy Day on March 21 brought together multi-disciplinary researchers and community organizations to better address and discuss concerns of environmental health impacts, specifically those centered around water safety and contamination issues in the Central Valley.

In California, about 20 percent of all groundwater is contaminated, impacting safe drinking water, as well as water for agriculture and recreational purposes. Contamination can come from pesticides, toxic metals, chemicals in personal care products or a change in climate.

There are a variety of human health issues prevalent in the Central Valley including infant death syndrome, blue baby syndrome, a syndrome associated with nitrates from drinking water decreasing the body’s capacity to carry oxygen, developmental cancer and immunological problems. However, they have not been scientifically proven to correlate with exposure to environmental risks.

“People don’t know how to decide if their water is safe to drink, and the lack of information can cause fear and concern that feeds the rumor mill on health impacts,” said Ryan Jensen, a community water solutions manager at the Community Water Center (CWC).

Attendants of the event included researchers with pilot projects at the center to community stakeholders and outreach organizations such as CWC and the Environmental Justice Coalition for Water.

The goal of EHS Academy Day was to bring together researchers in the field of environmental health and community outreach members to create an open dialogue about concerns specific to Sacramento and the San Joaquin Valley. In addition, all members were invited to a field trip to Vet Med Sciences 3B to see the fish facility that supplies models for research about impacts of water contamination on health.

“The questions we want to pose include: how can researchers engage with communities and make it culturally relevant, what’s the public health impact of certain chemicals that cause latent health effects and how do scientists go about proving or associating certain chemicals with human health impacts,” said Jonathan London, an associate professor of human ecology and community and regional development at UC Davis.

Community members were able to voice their concerns about the lack of access to safe drinking water for rural, farming and underserved populations.

Researchers at the Environmental Health Science Center (EHSC) presented the history and importance of using fish model systems to study environmental health.

Studying adverse effects of contaminants in aquatic environments and fish models in the Sacramento River and San Francisco Estuary can be applied to humans as well because of our exposure to the same water.

After an experiment observing the embryos of fish placed in specific sites along the San Francisco Estuary, concerning findings suggested something in the water is inhibiting proper growth and development of the fish. Genetic and hormonal factors were affected, as some fish had a lack of body development in embryos. In one case, immature eggs were found in testes of male fish.

Academy Day presented the science behind pilot projects as well as generated questions for an environmental health scientist. The aim was to get individuals thinking about how scientists may engage in community related issues and how community issues can generate questions about science and policy.

Environmental health is associated with public health, just more broadly defined. It is associated with how the environment influences human health and disease. Humans can be exposed to risk factors in their home, community and workplaces. Examples include air pollution, chemicals from pesticides and inadequate water and poor sanitation.

“Our mission is to promote and protect the wellbeing of all species and their environments,” said Swee Teh, the director of the Aquatic Health Program and an adjunct professor in the UC Davis Department of Anatomy, Physiology and Cell Biology.

Teh highlighted important ongoing projects including researching natural toxic algal blooms in the water as well as the impact of plastic debris infiltration of aquatic habits globally.

“The first toxic algae sighting was in 1999, and has become increasing in size and frequency in Delta and Bay region over the years,” Teh said.

These sites can shift due to water level and climate, especially cycles in drought and rain. Factors that contribute to toxic algae include water level and temperature. The study of plastic debris infiltration on aquatic habitats globally is significant because various plastics are ingested by hundreds of species.

“Large plastics cause strangulation of aquatic organisms,” Teh said. “Micro-plastics, plastic chemicals, are toxic in aquatic life and can affect development and behavior.”

The ingestion of large plastics can cause a bird or fish to think it is full. Since plastic doesn’t degrade easily and stays in the stomach, the animal dies of starvation.

Academy Day opened the doors for communication between researchers and community outreach groups. In addition, the researchers were able to hear the needs and concerns within the environmental health community.

“Notice that many questions generated from different groups can be applied to short term and long term time scale,” London said. “For example, the same issue such as pesticides association with human health may be immediate for scientists but long term for policy.”

Groups such as the CWC perform community outreach, such as community meetings, encouraging people to participate in policy in Sacramento, and bringing people to communities impacted from these factors, specifically those lacking safe and affordable drinking water.

“We provide state-wide advocacy to insure that everyone has basic access to safe water because often decision makers are not responsible to the needs of communities like farmers and low income families,” Jensen said.

Written by Shivani Kamal — science@theaggie.org

UC Davis, CSU Long Beach scientists discover why pandas are black and white

Pandas, while charismatic and fascinating, have tantalized humankind with one age-old question: why are they black and white? A new study conducted by scientists at UC Davis and CSU Long Beach has presented us with the answer to this enigma.

“We started by breaking down a general mammalian carnivore body into 13 regions and a general face into 12 regions,” said Theodore Stankowich, co-author of the study and an assistant professor at CSU Long Beach. “We then gathered about 2,500 photos of animals covering 195 species of mammalian carnivores, and gave each body region a color score in every picture. We compared these colors to the environmental factors, like snowfall, temperature, habitat type that each species experienced, as well as the type of social system they live in.”

According to the researchers, examining each region of the panda’s body independently was a major asset in the success of this study. Using this approach, researchers could assign different functions to different regions of the panda body by comparing them to those of related species.  

“If one tries to find similar species to the great panda, there are virtually none,” said Tim Caro, the lead author of the paper and a professor in the UC Davis Department of Wildlife, Fish and Conservation Biology. “But if one breaks up the body into regions — say white backs, black legs — there are many carnivores with similar coloration in those areas. Now one can ask what biological factors are associated with darks legs and white backs across carnivores.”  

The scientists found that the panda’s face, stomach, neck and hind were white so the the panda could camouflage in the snow. The arms and legs were black so that it could hide from predators in the shade.

This combination of black and white coloration is due to an interesting handicap of the great panda. Because the great panda consumes a very low-quality diet of bamboo, it cannot hibernate and must remain active all year. To get a sufficient amount of bamboo, it lives in both shady and snowy habitats throughout the year and therefore requires the dual coat coloration to hide from predators in both environments.

“Their body coloration is really a compromise between those two habitats to be camouflaged from potential predators during the entire year,” Stankowich said.

That still leaves the question of the panda’s endearing black eye patches and dark ears. The scientists determined that these regions of the panda’s head signified the function of communication. The dark eye patches help pandas recognize one another or signal aggression towards competitors, while the dark ears serve as a warning for predators.

“Now when someone wonders ‘why does a panda look like that?’ they actually have an answer,” said Zoe Rossman, another co-author of the paper. “It’s an easy way to introduce or expand on knowledge of evolution and animal behavior from kids to adults, and the more people know about these topics, the more people will hopefully care about protecting animals and the environment.”
Written by: Harnoor Gill — science@theaggie.org