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A record-breaking development in laser technology could help support the development of smaller, cheaper, more easily-fabricated optical and quantum technologies, its inventors say.

Researchers from the University of Glasgow have designed and built a narrow-linewidth laser on a single, fully integrated microchip that achieves the best performance ever recorded in semiconductor lasers of its type.

It could help overcome many of the barriers which have prevented previous generations of this type of monolithic semiconductor laser technology from being more widely adopted.

In the future, the new laser system could find applications in cutting-edge technologies such as advanced communication systems and unbreakable quantum cryptography.

The team's new system, which they call a "topological interface state extended laser with optical injection locking," or MOIL-TISE, is capable of producing a narrower, purer laser light than any previous distributed feedback (DFB) laser system.

The linewidth of a laser is one measure of the purity of its light. Narrower lasers are produced with more stable beams, which fluctuate very little in their operating frequencies. The team's MOIL-TISE system is capable of producing a linewidth of just 983Hz, a significant advance on monolithic DFB lasers currently on the market, which operate at the MHz range.

The development of the MOIL-TISE system on a single integrated chip is discussed in a paper titled "Narrow-linewidth monolithic topological interface state extended laser with optical injection locking," in Science Advances.

Previous high spectral purity lasers faced a major challenge: balancing top-level performance with compact design. To achieve efficiency, designers often relied on hybrid integration and bulky external components, which limited their practicality and restricted their potential in on-chip integrated applications.

The team describes how they utilized the facilities of the University of Glasgow's James Watt Nanofabrication Center to fabricate the MOIL-TISE device on a semiconductor substrate composed of indium phosphide.

The system's performance is enabled by its uniquely-shaped design, which breaks the chip into three regions, each with their own optical phase, specifically tuned to keep the light evenly distributed between them. Combined with a device called a micro-ring resonator integrated into the chip, the system can internally recycle light to stabilize its performance and enable the system's tightly-focused linewidth.

The University's Critical Technologies Accelerator (CTA)'s Dr. Xiao Sun is the paper's first and corresponding author. He said, "The University of Glasgow is unique in the UK in that it's possible to take a project like this from an initial idea to a fully-featured prototype without leaving our campus.

"The James Watt Nanofabrication Center enabled us to design, fabricate and test our MOIL-TISE system, dramatically accelerating the research process.

"This research represents a great example of the kind of breakthroughs that the Critical Technologies Accelerator is working to make. Being able to fabricate this at the JWNC using technology which is commercially available shows that industry could easily start to make their own MOIL-TISE-based devices easily and affordably in the years to come."

Professor Lianping Hou of the James Watt School of Engineering is the paper's co-corresponding author. He said, "Our MOIL-TISE laser makes three significant breakthroughs and improvements in this field. It's the first monolithic device of its kind, with every component integrated on a single chip.

"It can create a laser with remarkable frequency purity, the highest ever achieved in a monolithic distributed feedback laser of this kind. It is also capable of easily switching between optical phases, a property required in the quantum key distribution systems which will underpin the unbreakable encryption and communication devices of the future."