Schematic showing the “Dirac cones” through which the light passes through the holes in the semiconductor membrane. All light emitted from those points are in phase and optically the same. (Image courtesy of the Kanté group)Next-gen lasers
Despite the vast array of applications ushered in by the invention of the laser — from surgical tools to barcode scanners to precision etching — there have been persistent limits to its use. The coherent, single-wavelength directional light that is a defining characteristic of a laser starts to break down as the size of the laser cavity increases, requiring external amplification.
Berkeley engineers led by Boubacar Kanté, associate professor of electrical engineering and computer sciences, have created a solution: a new type of semiconductor laser that can emit a single mode of light while maintaining the ability to scale up in size and power.
Their invention, dubbed Berkeley Surface Emitting Lasers (BerkSELs), was designed with an innovative membrane perforated with evenly spaced and same-sized holes that are etched using lithography. The membrane — made of a 200-nanometer-thick layer of indium gallium arsenide phosphide, a semiconductor commonly used in fiber optics and telecommunications technology — enables the single-mode light emission because of the physics of the light passing through the holes. The laser emits a consistent, single wavelength, regardless of the size of the cavity, allowing it to cover longer distances for many applications.
“Increasing both size and power of a single-mode laser has been a challenge in optics since the first laser was built in 1960,” said Kanté. “Six decades later, we show that it is possible to achieve both these qualities in a laser.”
The study’s co-lead authors are Ph.D. student Rushin Contractor, Wanwoo Noh (Ph.D.’22 EECS) and postdoctoral researcher Walid Redjem. Scott Dhuey, Wayesh Qarony and Adam Schwartzberg from Berkeley Lab and Ph.D. student Emma Martin also contributed to the study.
Learn more: New single-mode semiconductor laser delivers power with scalability; Scalable single-mode surface-emitting laser via open-Dirac singularities (Nature)