Researcher looks to identify physics of ultra-small laser with funding from ORAU

UAB Physics researcher continues to identify inexpensive ways to laser print with small functional devices.

Krishen Appavoo streamKannatassen “Krishen” AppavooOak Ridge Associated Universities has awarded competitive research grants to 36 junior faculty from its member institutions, including University of Alabama at Birmingham Assistant Professor Kannatassen “Krishen” Appavoo for his research on “Nanoscale Quantum Properties of Solution-Processed Lasers.”

Appavoo’s research hopes to capitalize on understanding the lasing process that occurs in randomly arranged nanospheres since the lasing process occurs with few orders of magnitude lower in optical energy requirements than previously demonstrated.

“Most systems have a linear response, with a small perturbation inducing a proportionally small response,” said Appavoo, a junior faculty member in the UAB College of Arts and Sciences Department of Physics. “We believe this research project will provide fundamental physical insights into the nanoscale quantum optical properties of solution-processed thin film of nanostructure assemblies.”

Discoveries through Appavoo’s research play a role in the manufacturing method to make nano-composite lasing material cheaper rather than using expensive tools such as electron-beam lithography to fabricate nano-architectured lasing materials. This means the process could be scaled using a printing or roll-to-roll technique to create nanoscale functional devices.

The lasing process is highly sensitive to its environment. Since lasing occurs at the nanostructure level, the films could be used to detect the presence of molecules that might bind to the surface. As the molecules bind to the surface, the lasing process will stop, providing molecular detection. Potentially, the surfaces of these nanospheres can be functionalized to respond to specific binding events where only these events will trigger a change in the lasing process.

Two years ago, Appavoo and his colleagues discovered that when nanospheres an average size of 40 nanometers are made into a thin film they would exhibit lasing. The films that were made had thicknesses of around 120 nanometers, one of the thinnest films that has ever been made. This implied that a new physics phenomenon was taking place because most thin films would require to be thicker for lasing to occur. It was found that the key criterion for lasing to occur is that the nanospheres should be randomly arranged within the film.

Lasing systems that are exceptions to this rule, such as a small external stimulus or energy costs triggering large macroscopic responses, are highly desirable for integration into high-sensitivity detectors, light absorbers and modulators.

“Predicting parameters that create nonlinearity is difficult,” Appavoo said. “With recent progress in several key technologies, we can now think about methods for designing and testing materials with nonlinear, or emergent, properties.”

Recent technological advances include high-resolution lithography, self-assembly and computational electrodynamics. The goal of Appavoo’s research at ORAU is to unravel what parameters are essential to trigger the lasing process. Specific studies will include size effects; how the presences of nanosphere of a different material can change the wavelength (color) of the emission, or lasing; correlating the degree of “randomness” with the efficiency of this lasing mechanism; and resolving where light first emanates in those random nanosphere assemblies.

The annual grants are made through the company’s Ralph E. Powe Junior Faculty Enhancement Awards program that provides funds to enrich the research and professional growth of young faculty.

A total of $180,000 in seed money was granted to enhance research during the early stages of the during the early stages of the recipients’ careers. Each recipient’s institution matches the ORAU award with an additional $5,000, making the total prize worth $10,000 for each winner. Winners may use the grants to purchase equipment, continue research, or travel to professional meetings and conferences. 

Since the program’s inception, ORAU has awarded 698 grants totaling more than $3.4 million. Including the matching funds from member institutions, ORAU has facilitated grants worth more than $6.9 million. Appavoo is the first junior faculty member in the UAB Department of Physics to receive the award.

“The Powe Awards program is very popular and beneficial to our member universities because it provides an opportunity for young faculty members to further their research careers and helps them identify potential funding avenues,” said Arlene Garrison, ORAU vice president, University Partnerships Office. “ORAU is proud to recognize the research and professional growth of these emerging leaders as they support the future of science and technology.”

The awards recognize faculty members for their work in any of five science and technology disciplines: engineering or applied science; life sciences; mathematics and computer science; physical sciences; and policy, management or education.

The awards, now in their 28th year, are named for Ralph E. Powe, who served as the ORAU councilor from Mississippi State University for 16 years. Powe participated in numerous committees and special projects during his tenure and was elected chair of ORAU’s Council of Sponsoring Institutions. He died in 1996.