Recently, a team of researchers from the Korea Advanced Institute of Science and Technology (KAIST) published an innovative study announcing that they have successfully developed the world's first chip-based mid-infrared Brillouin laser. Relying on an Ultra-high-Q (UHQ) micro-optical resonator, this laser not only improves the precision of mid-infrared photon control to an unprecedented level, but also dramatically lowers the start-up power threshold of the laser.
The mid-infrared band (3-5 μm) has long been known as the "molecular fingerprint identification band", which is the key region of molecular vibration and rotation spectra. It plays an irreplaceable role in molecular sensing, bio-imaging, environmental monitoring and even quantum computing. However, the development of chip-scale photonics devices in this band has been lagging behind due to the limitations of material absorption, microstructure fabrication precision, and high loss issues, especially the lack of ultra-high Q resonant cavities as the core component, which has become the biggest bottleneck for the constraints of mid-infrared on-chip integration technology.
This research breaks this limitation. The research team innovatively adopted a non-traditional processing method to realize high-precision optical waveguide structure construction without destroying the integrity of the material. This approach is different from the traditional etching and stripping process, but through the spontaneous film-forming morphology during the material deposition process, the optical waveguide geometry of the internal multilayer structure is constructed. In this way, the team has successfully fabricated a mid-infrared resonant cavity with a quality factor of 38 million, which is more than 30 times higher than previous results, and reduced the propagation loss to only 0.52 dB/m, which is close to the performance limit of the world's best mid-infrared optical fiber.
