Yu, Yuan PT-symmetry OEO.mp4 A stable 17.74-GHz microwave signal generated by the OEO with selective PT-symmetry breaking . Microwave and RF Photonics 2019-07-23
    https://opticapublishing.figshare.com/articles/media/PT-symmetry_OEO_mp4/7642253
10.6084/m9.figshare.7642253.v1