Sputtered aluminum nitride waveguides achieve record low propagation loss in telecom spectrum

A collaboration between AMO GmbH and Fraunhofer IAF demonstrates the potential of sputtered aluminum nitride for photonic applications in the telecom spectrum.

Aluminum nitride (AlN) is emerging as an outstanding material for photonic waveguide applications. The best results to date have been achieved with AlN grown by metal organic chemical vapor deposition (MOCVD), while sputtered AlN has so far struggled with higher optical losses. Researchers at AMO GmbH and Fraunhofer IAF have now achieved a significant milestone with the successful fabrication of sputtered aluminum nitride waveguides with unprecedented low propagation losses. These results, published in Optics Express, demonstrate that sputtered AlN is now a competitive option for photonic applications in the telecommunications spectrum.

This breakthrough was made possible by combining Fraunhofer IAF’s expertise in high-quality sputtered AlN film deposition with AMO GmbH’s advanced waveguide fabrication and testing capabilities. Using reactive DC magnetron sputtering at 700°C, the researchers achieved a highly optimized polycrystalline AlN film on an oxidized silicon substrate, overcoming traditional limitations of sputtered films. The films where then used for fabricating uncladded AlN waveguides with different geometries for the C- and O- telecom bands.

The waveguides showed propagation losses of only 0.137 dB/cm at 1310 nm and 0.154 dB/cm at 1550 nm in TE polarization – the lowest losses ever recorded for sputtered AlN waveguides in telecom bands. These results are comparable to those of AlN waveguides made with MOCVD-grown AlN, but with the added benefits of a sputtering-based manufacturing technology, such as lower deposition temperatures, reduced cost and broader substrate compatibility.

“These results represent a significant step forward in integrated photonics,” says Dr. Stephan Suckow, Head of the Nanophotonics Group at AMO GmbH. “Our success with sputtered AlN not only demonstrates its viability for low-loss waveguiding in the telecom spectrum but also highlights its potential for scalable, cost-effective production of integrated photonic devices – without requiring sapphire substrates like for MOCVD.”

This research work received funding by the German Federal Ministry for Education and Research (BMBF) in the project ATIQ under grant numbers 13N16116 and 13N16130.

Bibliographic information

“Sputtered aluminum nitride waveguides for the telecommunication spectrum with less than 0.16 dB/cm propagation loss”
Radhakant Singh, Mohit Raghuwanshi, Balasubramanian Sundarapandian, Rijil Thomas, Lutz Kirste, Stephan Suckow, and Max C. Lemme
Optics Express 32, 46522 (2024)
https://doi.org/10.1364/OE.538852