Authors: Maodong Gao, Qi-Fan Yang, Qing-Xin Ji, Heming Wang, Lue Wu, Boqiang Shen, Junqiu Liu, Guanhao Huang, Lin Chang, Weiqiang Xie, Su-Peng Yu, Scott B. Papp, John E. Bowers, Tobias J. Kippenberg, Kerry J. Vahala
Published: 2022-06-09
DOI: 10.1038/s41467-022-30966-5
Source: Full article
AbstractOptical microresonators with high quality (Q) factors are essential to a wide range of integrated photonic devices. Steady efforts have been directed towards increasing microresonator Q factors across a variety of platforms. With success in reducing microfabrication process-related optical loss as a limitation of Q, the ultimate attainable Q, as determined solely by the constituent microresonator material absorption, has come into focus. Here, we report measurements of the material-limited Q factors in several photonic material platforms. High-Q microresonators are fabricated from thin films of SiO2, Si3N4, Al0.2Ga0.8As, and Ta2O5. By using cavity-enhanced photothermal spectroscopy, the material-limited Q is determined. The method simultaneously measures the Kerr nonlinearity in each material and reveals how material nonlinearity and ultimate Q vary in a complementary fashion across photonic materials. Besides guiding microresonator design and material development in four material platforms, the results help establish performance limits in future photonic integrated systems.