Left to right: Research contributors and Lehigh electrical and computer engineering graduate students Ji Chen, Liang Gao and Yuan Jin stand in the Terahertz Photonics laboratory of Sushil Kumar in the Sinclair Building at Lehigh University. Credit: Sushil Kumar, Lehigh University
The ability to harness light into an intense beam of monochromatic radiation in a laser has revolutionized the way we live and work for more than fifty years. Among its many applications are ultrafast and high-capacity data communications, manufacturing, surgery, barcode scanners, printers, self-driving technology and spectacular laser light displays. Lasers also find a home in atomic and molecular spectroscopy used in various branches of science as well as for the detection and analysis of a wide range of chemicals and biomolecules.
Lasers can be categorized based on their emission wavelength within the electromagnetic spectrum, of which visible light lasers—such as those in laser pointers—are only one small part. Infrared lasers are used for optical communications through fibers. Ultraviolet lasers are used for eye surgery. And then there are terahertz lasers, which are the subject of investigation at the research group of Sushil Kumar, an associate professor of Electrical and Computer Engineering at Lehigh University.
As it propagates, terahertz radiation is absorbed by atmospheric humidity. Therefore, a key requirement for such lasers is an intense beam such that it could be used for optical sensing and analysis of substances kept at a standoff distance of several meters or more, and not be absorbed. To this end, Kumar's research team is focused on improving their intensity and brightness, achievable in part by increasing optical power output.
In a recent paper published in the journal Nature Communications, the Lehigh team—supervised by Kumar in collaboration with Sandia National Laboratories—reported on a simple yet effective technique to enhance the power output of single-mode lasers that are "surface-emitting" (as opposed to those using an "edge-emitting" configuration). Of the two types, the surface-emitting configuration for semiconductor lasers offers distinctive advantages in how the lasers could be miniaturized, packaged and tested for commercial production.