Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Highly-twisted states of light from a high quality factor photonic crystal ring



Xiyuan Lu, Mingkang Wang, Feng Zhou, Mikkel Heuck, Wenqi Zhu, Vladimir Aksyuk, Dirk Englund, Kartik Srinivasan


Twisted light with orbital angular momentum (OAM) has been extensively studied for applications in quantum and classical communications, microscopy, and optical micromanipulation. Ejecting the naturally high angular momentum whispering gallery modes (WGMs) of an optical microresonator through a grating-assisted mechanism, where the generated OAM number ($l$) is the difference of the angular momentum of the WGM and that of the grating, provides a scalable, chip-integrated solution for OAM generation. However, demonstrated OAM microresonators have exhibited a much lower quality factor ($Q$) than conventional WGM resonators (by $>100\times$), and an understanding of the ultimate limits on $Q$ has been lacking. This is crucial given the importance of $Q$ in enhancing light-matter interactions, such as single emitter coupling and parametric nonlinear processes, that underpin many important microresonator applications. Moreover, though high-OAM states are often desirable, the limits on what is achievable in a microresonator configuration are not well understood. Here, we provide new physical insight on these two longstanding questions, through understanding OAM as one case of mode coupling inside a photonic crystal ring, and linking it to the commonly studied case of coherent backscattering between counter-propagating WGMs. In addition to demonstrating high-$Q$ ($\gtrsim10^5$), high-OAM ejection efficiency ($\gtrsim50\%$), and high-OAM number (up to $l$=60), our empirical model is supported by experiments and provides a quantitative explanation for the behavior of $Q$ and OAM ejection efficiency with $l$ for the first time. The state-of-the-art performance and new understanding of the physics of microresonator OAM generation will open new opportunities for realizing OAM applications using chip-integrated technologies.
Nature Communications


orbital angular momentum, photonic crystal ring, high quality factor


Lu, X. , Wang, M. , Zhou, F. , Heuck, M. , Zhu, W. , Aksyuk, V. , Englund, D. and Srinivasan, K. (2023), Highly-twisted states of light from a high quality factor photonic crystal ring, Nature Communications, [online],, (Accessed May 26, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created February 27, 2023, Updated April 9, 2024