Researchers at the University of Sydney have demonstrated a new way to suppress noise in microchip-scale Brillouin lasers by introducing nanoscale “speed bumps” inside the devices’ optical cavity.
According to the university, the advancement could support future technologies including quantum computing, advanced navigation systems and high-speed communications, with potential benefits for precision-driven sectors such as manufacturing.
In the study, the team addressed a long-standing challenge known as Brillouin cascading, where unwanted parasitic light modes emerge and degrade laser performance.
Lead author and PhD candidate Ryan Russell said these additional modes introduce noise and “steal energy” from the primary laser mode, limiting the device’s usefulness in real-world applications.
To overcome this, researchers used photonic bandgap engineering to write nanoscale Bragg gratings, which features more than 100 times smaller than a human hair, directly into the laser cavity.
Co-author Dr Moritz Merklein said the gratings create a precise “dead zone” that blocks parasitic modes at their origin without disrupting the fundamental mode.
Researchers said the approach increased the threshold for Brillouin lasing and boosted the power of the desired output.
It noted that the method is also reconfigurable, allowing the Bragg gratings to be written, erased or re-tuned without refabricating the device.
Russell said this provides a flexible framework for controlling optical processes on photonic chips and could lead to cleaner quantum light sources and frequency comb lasers.
Professor Ben Eggleton, research group lead at the University of Sydney, said the ability to engineer the density of states inside a resonator opens the door to new classes of photonic technologies.
The paper is published in APL Photonics.
