Trying to observe something about 10,000 times smaller than the width of a human hair is a challenge for scientists, but Yohannes Abate, assistant professor in the Department of Physics and Astronomy at California State University, Long Beach (CSULB) has found a way.
“What we do is categorized as nano-optics, which means investigating optical properties of very small particles called nanoparticles, which are the size of 10 to the minus 9th power of a meter,” he said. Because nanoparticles are so tiny, they can’t be seen with regular optical microscopes, but they can possess new and intriguing phenomena that interest academics as well as industry.
At the nanoscale, electrons on the surface of a metal demonstrate a phenomenon called plasmons, he continued. “Plasmons are collective oscillations of electrons on the surface of a metal and you can actually capture the properties of the oscillations in a nanometer-size scale by their near-field distributions.” Abate built a highly advanced near-field optics laboratory at CSULB based on a high spatial resolution near-field microscope that condenses a laser beam through a variety of lenses spread across a large table, eventually focusing on a tiny point that a detector can use to record the plasmons in action.
Communications technology investigators are very interested in knowing how plasmons can be used to manipulate light to tranmsit signals, since using the speed of light rather than slower electrical current has huge benefits, he said. “Also, you have no heating effect, which you have with current. There is a huge interest in this for communications purposes. The problem is that the basic physics of these plasmons is not well understood, so that is our goal.”
Another organization interested in advancing nanotechnologies is the U.S. Department of Defense (DoD), which through the U.S. Army Research Office has provided a three-year, $589,999 grant to Abate as principal investigator (PI) and Shahab Derakhshan, CSULB assistant professor of chemistry, as co-PI. Derakhshan is an expert in crystal structure determination, electronic structure calculations and syntheses of novel oxides with phase transition properties that would be investigated with Abate’s microscope.
The grant will aid in their research and most importantly, it will help prepare students for nanotechnology careers and studies either in academia or industry. In addition, it will allow Abate to purchase lasers that operate at wide range of wavelengths, expanding the capability of his microscope.
An important part of their research focuses on a property called phase transition, in which a material changes its physical state such as from an insulator to a conductor, depending on its temperature. “You heat it up and it becomes metal, you cool it down and it acts like an insulator (similar to electrical properties of paper or glass), and so forth,” Abate said. “The problem is that while they exhibit these kinds of properties, why they do that on the nano scale remains largely unknown.”
This also has attracted considerable attentions due to its technological values, Abate said. “Electronic devices such as ultra-fast switches, oscillators, memory devices, optical devices, thermal sensors, and chemical sensors are a few examples of applications that utilize of phase transitions.”
Originally from Ethiopia, Abate earned his bachelor’s degree at Addis Ababa University; his master’s at the University of the Philippines, Diliman; and his Ph.D. at the University of Iowa. He did his postdoctoral studies at UC Berkeley with Professor Stephen Leone, whom Abate called “one of the gurus of spectroscopy.” During Abate’s experiences at Berkeley and a brief period at the Max Planck Institute in Germany, he contributed to developing the technique that he uses today.
“There are only handful of laboratories in the world which possess such near-field microscope and the expertise we have,” he said, “and so this gives us a very strong advantage to look at these novel systems.”