Scientists have achieved a significant breakthrough in the field of UV photonics by creating chip-based optical resonators that operate in the ultraviolet (UV) and visible regions of the spectrum with a record low ultraviolet light loss. The development of these resonators opens up possibilities for creating miniature chip-based devices and advancements in fields such as spectroscopy, underwater communication, and quantum information processing.

UV photonics, although less explored compared to telecommunications and visible photonics, is crucial for accessing certain atomic transitions in quantum computing and exciting specific fluorescent molecules for biochemical detection. The newly developed resonators establish a foundation for constructing photonic circuits that operate at UV wavelengths.

The researchers used thin alumina films to build the microresonators, using an atomic layer deposition (ALD) process. Alumina, with its wide bandgap and transparency to UV photons, proved to be an ideal material for reducing light loss. By carefully optimizing the design and fabrication techniques, the scientists achieved low loss at UV wavelengths.

The microresonators were produced using an etching process to create a rib waveguide structure, which allowed for light confinement. The researchers conducted simulations to determine the optimal etching depth that would achieve a balance between light confinement and minimization of losses through scattering.

The team also successfully constructed ring resonators based on their calculations. These ring resonators exhibited exceptional quality factors (Q) in the UV and blue bands, indicating a reduction in light loss. Achieving a high Q factor is essential for precise control of wavelengths and the creation of integrated UV light sources in photonic integrated circuits.

The discovery of chip-based optical resonators with low UV light loss marks a critical milestone for UV photonics. The possibilities of applying structures developed for telecommunications and visible wavelengths, such as frequency combs and injection locking, now extend to the UV band. With the use of alumina compatible with CMOS, integrating UV photonics with existing technology becomes more feasible.

The research team is currently focused on improving the tunability of alumina-based ring resonators at various wavelengths. Their goal is to establish a complete UV system based on photonic integrated circuits with precise wavelength control and modulators.

Article Reference: He, C., et al. “Ultra-high Q alumina optical microresonators in the UV and blue bands.” Optica.

Source: Optica Publishing Group