A research team has successfully developed the first-ever chip-integrated erbium-doped waveguide laser, potentially supporting future advancements in optical communications and sensing technologies.
Led by Yang Liu and Professor Tobias Kippenberg at EPFL, the work, published in Nature Photonics, combines wide wavelength tunability with chip-scale photonic integration to build on previous technological research.
By using advanced fabrication techniques to create a metre-long optical cavity on a compact silicon nitride photonic integrated circuit, the researchers were able to develop a technology that could help to meet the pressing need to miniaturise fibre lasers to a chip-scale level, and particularly erbium-based fibre lasers which are known for their high coherence and stability.
These needs exist due to the growing demand for laser-based applications, which make fibre lasers, doped with rare-earth elements, vital in industrial cutting, welding, and marking because of their high power output, efficiency, and stability.
Yang Liu commented: “We were able to design the laser cavity to be metre-scale in length despite the compact chip size, thanks to the integration of these microring resonators that effectively extend the optical path without physically enlarging the device.”
The process involved implating high-concentration erbium to form the active gain medium, and integrating a III-V semiconductor pump laser to produce the laser beam. The researchers also used microring-based Vernier filters to support precise wavelength control, enabling stable, single-mode lasing with a narrow intrinsic linewidth of 50Hz and significant side mode suppression.
Results showed that the chip-scale erbium-based fibre laser could deliver over 10mW output power and a side mode suppression ratio greater than 70dB. This means that it is capable of outperforming many conventional systems. The microring-based Vernier was also shown to provide broad wavelength tunability across 40nm within the C- and L-bands, surpassing legacy fibre lasers and remaining compatible with current semiconductor manufacturing processes.
Such conditions mean the development is evidence that the miniaturisation and integration of erbium fibre lasers into chip-scale devices is feasible. Such technological capabilities can help to reduce costs and enhance portability and integration across telecommunications, medical diagnostics, and consumer electronics. At the same time, it can help to scale down optical technologies for applications such as lidar, microwave photonics, optical frequency synthesis, and free-space communications.
Yang Liu concluded: “The application areas of such a new class of erbium-doped integrated lasers are virtually unlimited.”
Lead image: PEPFL/Andrea Bancora/Yang Liu
