This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Over the past two decades, photonic-crystal surface-emitting lasers (PCSELs) have shown promise as a type of advanced semiconductor laser useful in defense- and aerospace-related applications. Typically, these devices are made with photonic crystal patterns that repeat across the area of the device.
But new research from the lab of electrical and computer engineering professor Kent Choquette has demonstrated a quasi-periodic photonic-crystal surface-emitting laser (QPCSEL). Fabricated with their buried dielectric platform, the group's device highlights a new avenue for creating tunable, more reliable semiconductor lasers. Their findings appear in Applied Physics Letters.
One challenge for the PCSEL field has been its reliance on geometry-dependent device fabrication. While a photonic crystal pattern can be optimized for certain properties, researchers have limited options for fabricating new devices with a wide variety of pattern shapes and sizes. Wanting to introduce a more versatile method, graduate student Erin Raftery began with a goal: to make a periodic structure nonperiodic.
Drawing inspiration from other work on topologically protected—or nonrepeating—patterns, Raftery integrated a similar patterning method with her group's existing buried dielectric platform, which they first demonstrated in 2025. While most layered semiconductor materials are fabricated by etching tiny holes vertically through the device, Raftery etched a silicon dioxide layer, which was then covered with epitaxial semiconductor, embedding it in the device. The resulting partially periodic structure lased successfully at room temperature.
The Illinois researchers' innovative approach is a practical route forward for high-performance, fully integrated QPCSELs that are versatile and geometry-independent. "We've demonstrated that we can have a nonperiodic pattern and more flexibility to tune it," Raftery said. "It's a different way of engineering the refractive index variation to get the properties we want from our lasers." In its current iteration, the platform's primary advantage lies in the versatility and uniformity of the buried dielectric photonic crystal pattern.
"Right now, you can only grow one kind of structure at a time, whereas we can mix and match on the same substrate," Choquette said. "This could allow us to build more reliable, better-performing lasers." Now, the Illinois Grainger engineers are turning their attention to making a more practical semiconductor laser. In the future, they hope to demonstrate an electrically injected diode—a more challenging pursuit with commercial implications.
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