• Chinese Optics Letters
  • Vol. 20, Issue 1, 011902 (2022)
Renhong Gao1、6, Ni Yao2, Jianglin Guan3、4, Li Deng3、4, Jintian Lin1、6、*, Min Wang3、4, Lingling Qiao1, Wei Fang5, and Ya Cheng1、3、4、6、7、8、9、**
Author Affiliations
  • 1State Key Laboratory of High Field Laser Physics and CAS Center for Excellence in Ultra-Intense Laser Science, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences (CAS), Shanghai 201800, China
  • 2Research Center for Intelligent Sensing, Zhejiang Lab, Hangzhou 311100, China
  • 3XXL—The Extreme Optoelectromechanics Laboratory, School of Physics and Electronic Science, East China Normal University, Shanghai 200241, China
  • 4State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
  • 5State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering, Zhejiang University, Hangzhou 310027, China
  • 6Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
  • 7Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
  • 8Collaborative Innovation Center of Light Manipulations and Applications, Shandong Normal University, Jinan 250358, China
  • 9Shanghai Research Center for Quantum Sciences, Shanghai 201315, China
  • show less
    DOI: 10.3788/COL202220.011902 Cite this Article
    Renhong Gao, Ni Yao, Jianglin Guan, Li Deng, Jintian Lin, Min Wang, Lingling Qiao, Wei Fang, Ya Cheng. Lithium niobate microring with ultra-high Q factor above 108[J]. Chinese Optics Letters, 2022, 20(1): 011902 Copy Citation Text show less

    Abstract

    We demonstrate integrated lithium niobate (LN) microring resonators with Q factors close to the intrinsic material absorption limit of LN. The microrings are fabricated on pristine LN thin-film wafers thinned from LN bulk via chemo-mechanical etching without ion slicing and ion etching. A record-high Q factor up to 108 at the wavelength of 1550 nm is achieved because of the ultra-smooth interface of the microrings and the absence of ion-induced lattice damage, indicating an ultra-low waveguide propagation loss of 0.0034 dB/cm. The ultra-high Q microrings will pave the way for integrated quantum light source, frequency comb generation, and nonlinear optical processes.

    1. Introduction

    A lithium-niobate-on-insulator (LNOI) wafer is considered as an important candidate platform for photonic integrated circuits (PICs), owing to its outstanding material properties featuring a broad transparency window (350 nm to 5 µm), a linear electro-optic effect, and a large second-order nonlinearity susceptibility (χ(2)=30pm/V)[15]. A wide range of high-performance device applications, such as waveguide/resonator optical frequency convertors, high-speed Mach–Zehnder modulators, and multiplexers, have been demonstrated due to the rapid developments in the ion-slicing technique and LNOI nanofabrication technology[623]. Among the various devices, optical waveguides with ultra-low propagation loss and high refractive index contrast are building elements for the realization of large-scale PICs[2428]. The propagation losses in optical waveguides are susceptible to sidewall roughness induced by the fabrication imperfection. To reduce the sidewall roughness of the waveguide, diamond-blade dicing, precision cutting, focused ion beam milling, argon ion milling, and chemo-mechanical polishing (CMP) have been successively used to etch the lithium niobate (LN) thin film into waveguides with smooth sidewalls to improve propagation losses[2934]. For instance, an ultra-smooth sidewall roughness as small as 0.1 nm has been achieved by CMP etching, leading to an ultra-low propagation loss of ridge waveguides of 0.027 dB/cm[25,35]. However, the minimum propagation loss of the waveguide determined by the intrinsic material absorption is only 0.001 dB/cm[36]. There is still room to reduce the propagation loss by improving the quality of LN thin film.

    Copy Citation Text
    Renhong Gao, Ni Yao, Jianglin Guan, Li Deng, Jintian Lin, Min Wang, Lingling Qiao, Wei Fang, Ya Cheng. Lithium niobate microring with ultra-high Q factor above 108[J]. Chinese Optics Letters, 2022, 20(1): 011902
    Download Citation