Low-loss erbium-incorporated rare-earth oxide waveguides on Si with bound states in the continuum and the large optical signal enhancement in them

Integrated optical amplifiers are essential building blocks for emerging applications of large-scale and complex silicon photonic integrated circuits. Single-crystal erbium-incorporated rare-earth oxide thin films epitaxially grown on silicon substrate could be a promising material candidate. Based on the mechanism of bound states in the continuum, we have developed a low-loss waveguide platform for such materials. The waveguides are formed by patterning a silicon nitride cap layer grown on a rare-earth oxide thin film on silicon-on-insulator substrate. Low propagation loss of 4.70 dB/cm has been obtained in waveguides with silicon nitride/rare-earth oxide/silicon layer stack thickness of 72 nm/90 nm/300 nm, width of 1.08 mu m, at a wavelength of 1445.8 nm. Optical signal enhancement in these waveguides upon optical pumping has been observed in a wide wavelength range of 1510 to 1560 nm, with a large peak enhancement of similar to 16 dB/cm around 1536 nm. Our results represent an important step towards the realization of high-performance monolithic-integrated optical amplifiers on Si. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Automated summary

Integrated optical amplifiers are crucial for large-scale and complex silicon photonic integrated circuits. A low-loss waveguide platform has been developed based on rare-earth oxide thin films grown on silicon substrates. Optical signal enhancement has been observed in waveguides with high peak enhancement in a wide wavelength range, showcasing progress towards high-performance monolithic-integrated optical amplifiers on silicon.