Tunable semiconductor lasing enabled by the aperiodic photonic crystal design

Researchers at Illinois Grainger have developed a silica-layer-based structure featuring partial periodicity, which demonstrates room-temperature lasing action.

The Illinois  approach is a route torward high-performance QPCSELs that are versatile and geometry independent

The past twenty years have witnessed the rise of photonic-crystal surface-emitting lasers (PCSELs) as a promising semiconductor laser technology, particularly for defense and aerospace sectors. A defining feature of these devices, in their conventional form, is the use of repetitively patterned photonic crystal structures on the surface.

But new research from the lab of electrical and computer engineering professor Kent D Choquette  has reported the successful demonstration of 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 and more reliable semiconductor lasers. Choquette is an Illinois Grainger Engineering professor of electrical & computer engineering and is affiliated with the Holonyak Micro & Nanotechnology Laboratory. Choquette holds the Abel Bliss Professorship in Engineering.

Their findings are published in Applied Physics Letters.

Aim: to make a periodic structure non-periodic

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 non-periodic.

Drawing inspiration from other work on topologically-protected — or non-repeating — 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 by epitaxial semiconductor, embedding it in the device. The resultant 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 non-periodic 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 that the buried dielectric photonic crystal pattern possesses.

“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. “We’ve demonstrated the physics,” Choquette said. “Now we need to demonstrate a practical device.”

Source: optics.org