Parity-Time Symmetric Optoelectronic Oscillator Based on an Integrated Mode-Locked Laser
Fang Zou, Lei Zou, Yun Lai, Changjian Xie, Jie Luo, Dušan Milošević, Lianshan Yan, Wei Pan, Yu Liu, Zizheng Cao, A.M.J. Koonen, Xihua Zou
Abstract
Originating from the non-Hermitian quantum mechanics, the parity-time (PT) symmetry has been extensively explored to ensure a stable single-mode oscillation for optoelectronic oscillators (OEOs), while avoiding additional extremely challenging ultrahigh-Q filters. Enabled by the emerging photonics integrated circuit (PIC) technology, we report the tunable PT-symmetric OEO by using an integrated mode-locked laser, as a striking advance to reduce the footprint of OEOs. Stable single-mode oscillating signal at 24.5 GHz has been generated with a phase noise of -108 dBc/Hz @ 10 kHz frequency offset. In particular, a tunable frequency range from 24 to 25 GHz is achieved by manipulating the injection currents into the well-designed on-chip linear laser cavity. This work exhibits a breakthrough in conceptual integrated microwave photonic devices, and also accelerates the real-world applications of fundamental physical theory of PT symmetry to information industry.