New Laser based on unusual physics phenomenon could improve telecommunications, and computing applications

This is a schematic of the BIC laser: a high frequency laser beam (blue) powers the membrane to emit a laser beam at telecommunication frequency (red). Credit: Kanté group, UC San Diego

Researchers at the University of California San Diego have demonstrated the world's first laser based on an unconventional wave physics phenomenon called bound states in the continuum. The technology could revolutionize the development of surface lasers, making them more compact and energy-efficient for communications and computing applications. The new BIC lasers could also be developed as high-power lasers for industrial and defense applications.

"Lasers are ubiquitous in the present-day world, from simple everyday laser pointers to complex laser interferometers used to detect gravitational waves. Our current research will impact many areas of laser applications," said Ashok Kodigala, an electrical engineering Ph.D. student at UC San Diego and first author of the study.



"Because they are unconventional, BIC lasers offer unique and unprecedented properties that haven't yet been realized with existing laser technologies," said Boubacar Kanté, electrical engineering professor at the UC San Diego Jacobs School of Engineering who led the research.

For example, BIC lasers can be readily tuned to emit beams of different wavelengths, a useful feature for medical lasers made to precisely target cancer cells without damaging normal tissue. BIC lasers can also be made to emit beams with specially engineered shapes (spiral, donut or bell curve) -- called vector beams -- which could enable increasingly powerful computers and optical communication systems that can carry up to 10 times more information than existing ones.

"Light sources are key components of optical data communications technology in cell phones, computers and astronomy, for example. In this work, we present a new kind of light source that is more efficient than what's available today in terms of power consumption and speed," said Babak Bahari, an electrical engineering Ph.D. student in Kanté's lab and a co-author of the study.

Bound states in the continuum (BICs) are phenomena that have been predicted to exist since 1929. BICs are waves that remain perfectly confined, or bound, in an open system. Conventional waves in an open system escape, but BICs defy this norm -- they stay localized and do not escape despite having open pathways to do so.

In a previous study, Kanté and his team demonstrated, at microwave frequencies, that BICs could be used to efficiently trap and store light to enable strong light-matter interaction. Now, they're harnessing BICs to demonstrate new types of lasers. The team published the work Jan. 12 in Nature.



Making the BIC laser
The BIC laser in this work is constructed from a thin semiconductor membrane made of indium, gallium, arsenic and phosphorus. The membrane is structured as an array of Nano-sized cylinders suspended in air. The cylinders are interconnected by a network of supporting bridges, which provide mechanical stability to the device.

By powering the membrane with a high frequency laser beam, researchers induced the BIC system to emit its own lower frequency laser beam (at telecommunication frequency).
"Right now, this is a proof of concept demonstration that we can indeed achieve lasing action with BICs," Kanté said.

"And what's remarkable is that we can get surface lasing to occur with arrays as small as 8 × 8 particles," he said. In comparison, the surface lasers that are widely used in data communications and high-precision sensing, called VCSELs (vertical-cavity surface-emitting lasers), need much larger (100 times) arrays -- and thus more power -- to achieve lasing.

"The popular VCSEL may one day be replaced by what we're calling the 'BICSEL' -- bound state in the continuum surface-emitting laser, which could lead to smaller devices that consume less power," Kanté said. The team has filed a patent for the new type of light source.

The array can also be scaled up in size to create high power lasers for industrial and defense applications, he noted. "A fundamental challenge in high power lasers is heating and with the predicted efficiencies of our BIC lasers, a new era of laser technologies may become possible," Kanté said.

The team's next step is to make BIC lasers that are electrically powered, rather than optically powered by another laser. "An electrically pumped laser is easily portable outside the lab and can run off a conventional battery source," Kanté said.
Story Source:
Materials provided by University of California - San Diego. Original written by Liezel Labios.

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Did Oil Production Cause 20th Century Earthquakes in California?

By: Alexandria Addesso

The more man finds new corners to cut in terms of the environment, the more planet Earth seems to strike back with ecological karma. For every action there is an equal and opposite reaction according to Newton, and we must be able to face the ramifications of our actions. For over a 150 years people have been drilling for oil, and new evidence has been uncovered concerning how it has affect the planet.

A recent study published in the Bulletin of the Seismological Society of America (BSSA) followed the correlation between 20th century oil extraction and earthquakes. The study focused on drilling done in the 1920s and 1930s in the County of Los Angeles that are linked to several devastating earthquakes. These earthquakes include the 1920 Inglewood earthquake, the 1929 Whittier earthquake, the 1930 earthquake in Santa Monica, and the most devastating 1933 Long Beach earthquake which had a 6.4 magnitude on the richter scale and killed 120 people.



"If you take our four-the 1920, 1929, 1930 and 1933 earthquakes out of the calculations as induced or potentially induced, it does call into question what the rate of natural earthquakes in the L.A. Basin really is," said U.S. Geological Surveyor Susan Hough. "Maybe the L.A. Basin as a geological unit is more seismically stable than we've estimated."

The U.S. Geological Survey team studied 22 earthquakes that took place during the 20th century and found that 13 of them were most likely connected to nearby “oil production activities”. The study attributed these earthquakes to “industry practices that are no longer employed (i.e., production without water reinjection), and do not necessarily imply a high likelihood of induced earthquakes at the present time." Yet, another study released last year by U.S. Geological Surveyors suggested that mid-20th century earthquakes in Oklahoma were caused by injecting wastewater into the earth to extract oil, unlike the oil production methods of the 1920s and 1930s but very similar to the fracking method used to extract oil today.



Fracking is a very controversial method of oil extraction because it can very easily taint the water supply of the surrounding area. In the past year, after much urging by environmental and civil rights groups , the Environmental Protection Agency (EPA) released a 1,000 page document confirming "specific instances" when fracking "led to impacts on drinking water resources, including contamination of drinking water wells." With this information as well as the oil extraction connections to earthquakes, it would appear that more concern would be raised about halting such projects. Yet, neither of the U.S. Geological Surveys mentioned any concerns with the current fracking method.

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California Gas: How And Why It Differs From The Rest Of The Nation

By: Alexandria Addesso

When I first arrived in Los Angeles, California a year ago I noticed many differences between my home coast back east. Although I wasn’t doing much driving I did notice the high gas prices at a time when gas was relatively low. I had long thought that New York City was the Mecca for exaggerated gas prices.

It took time and several conversations later before I found out why California’s gas prices were so much higher, about 63-90 cents more than the national average. California’s gas is different than what is used in the rest of the United States. California’s gas is known as a “special blend”. The state has the strictest gas standard’s, in the country which thus results in the use of some of the cleanest gas in the world.



In Los Angeles, the largest and most populous city in California, smog was once a serious issue. During World War II the air quality was so poor that it was suspected that the Japanese had perpetrated a chemical attack. Something had to be done to combat the pollution and thus gas regulations began to stricken.

So what is so special about California’s “special blend”? California uses reformulated gasoline to reduce smog-forming particulates and pollutants and combat damage to the ozone. Refineries have to use a specialized process to make this oxygenated blend, and only 12 refineries are able to make California-approved gas within the state. This “special blend” releases less emissions and has helped reduced the smog in Los Angeles by 40 percent in comparison to what it was during the 1970s as well as contributed to the high gas prices.



If this gasoline is such a healthier blend, many have begun to question why it isn’t used
throughout the country? For the simple reason that this “special blend” is more expensive to produce. And to expect large oil conglomerates to change to meet strict regulations is simply too much for the federal government to ask for. As in many other instances, money and the drive acquire more is the source. Stay curious.

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