Imagine a laser you can tune like a radio, smoothly changing its colour by turning a dial. Engineers today are aiming for such flexible and precise control with lasers smaller than a pinhead, which could lay the groundwork for future smartphone screens, data networks, medical diagnostics and environmental sensors.
But it’s not easy crafting a tuneable microlaser that’s also fast, efficient and stable. Most compact designs today achieve colour tuning by relying on mechanically driven structural changes, temperature changes or external optical components, noted Tim Colin Meiler, a former SINGA scholar at the A*STAR Institute of Materials Research and Engineering (A*STAR IMRE).
“However, these methods can be slow, energy-intensive or difficult to miniaturise further,” said Meiler. “In very small devices, it’s also challenging to maintain stable, high-quality laser emissions while tuning; it’s like trying to retune a guitar string without it going entirely off-tune.”
Supervised by A*STAR IMRE Optics and Electronics Division Director Arseniy Kuznetsov and former A*STAR IMRE Principal Scientist Ramón Paniagua-Domínguez, Meiler and A*STAR IMRE colleagues worked with researchers from Nanyang Technological University, Singapore, to develop a novel microlaser where light colour is tuned in the device itself, rather than after it is emitted. Their approach combines a responsive perovskite material—which can change its internal structure (phase), and therefore the colour of light it emits—with a carefully engineered optical cavity known as a bound state in the continuum (BIC).
“What makes our approach distinctive is how these two elements work together,” Meiler explained. “Instead of forcing the laser to adapt via external tuning, the material itself changes its emissions in a controlled way, while the BIC cavity efficiently traps light and keeps it tightly confined and coherent. This results in a compact design suitable for on-chip integration, with more tuning depth than conventional laser materials.”
To keep lasing emissions stable across phase transitions, the team also designed their optical cavity with a resonance that overlapped the perovskite’s optical gain across different temperatures. Like a radio with a strong signal lock, the cavity’s design helped maintain its alignment with drifting emission wavelengths.
With perovskite phase changes driven by an integrated microheater, the device demonstrated fast, smooth and reversible light wavelength control, switching between two emission states spanning 20 nm on millisecond timescales. Its phase transitions were highly stable, remaining reproducible over thousands of cycles and a week of vacuum testing.
Unexpectedly, the system also allowed continuous colour tuning between phases. “Phase transitions are usually thought of as abrupt changes, but with precise electrical control of the microheater, we observed intermediate states,” said Meiler.
Many technical hurdles remain for the device’s real-world implementation, including a very low operational temperature range and the need for advanced and scalable fabrication technologies. “However, such tuneable microlasers could be useful for on-chip communications, sensing, materials analysis, and advanced imaging or display technologies,” Meiler added.
The A*STAR researchers contributing to this research are from the A*STAR Institute of Materials Research and Engineering (A*STAR IMRE).
