Semiconductor lasers may soon become more adaptable and dependable thanks to a novel design that departs from the traditional repetitive patterns used to manipulate light.
Researchers at the University of Illinois have created a new type of photonic-crystal surface-emitting laser, or PCSEL, utilizing a partially non-repeating structure.
This innovation could eventually enable engineers to develop advanced lasers that are easier to fine-tune for a variety of uses.
Over the past twenty years, PCSELs have garnered increasing attention because they produce high-quality laser beams and hold potential for applications in aerospace and defense.
Typically, these lasers incorporate photonic crystals—miniature, intricately crafted structures that guide light within the device.
In conventional designs, the patterns within these photonic crystals repeat regularly throughout the device, a setup that works well but also imposes limitations. The laser’s performance is often heavily influenced by the precise geometry of the repeating pattern, making it challenging to create devices with diverse configurations and properties.
A team led by electrical and computer engineering professor Kent Choquette sought a more versatile approach. Graduate student Erin Raftery investigated whether a laser could operate effectively using a structure that isn’t entirely periodic.
Drawing inspiration from studies on aperiodic patterns, Raftery integrated this concept with a buried dielectric platform previously developed by the research group.
Instead of merely etching tiny holes straight through the semiconductor layers, they patterned a layer of silicon dioxide and then layered semiconductor material on top, effectively embedding the pattern within the device.
This process resulted in a quasi-periodic photonic-crystal surface-emitting laser, or QPCSEL. Significantly, the device successfully emitted laser light at room temperature, demonstrating its practicality under real-world conditions.
“We’ve shown that using a non-periodic pattern gives us more flexibility to tune the device,” Raftery explained. She noted that this design offers an alternative method to manage variations in the material’s refractive index, which governs how light propagates through the laser.
One key benefit is increased manufacturing flexibility. Traditional methods often limit researchers to fabricating a single pattern at a time, but the buried dielectric technique allows different patterns to be created on the same semiconductor substrate.
“Currently, you can only grow one type of structure at a time, but with this method, we can combine different patterns on the same chip,” Choquette said. This versatility could lead to lasers that are both more reliable and higher performing.
So far, the team has confirmed that the underlying principles work. Their next goal is to translate this concept into a practical device by developing an electrically powered laser diode.
If successful, this technology could pave the way for highly tunable semiconductor lasers suited for a broad spectrum of commercial and technological applications.