On-chip tunable parity‐time symmetric optoelectronic oscillator

Abstract

Parity‐time (PT) symmetry breaking offers mode selection capability for facilitating single‐mode oscillation in the optoelectronic oscillator (OEO) loop. However, most OEO implementations depend on discrete devices, which impedes proliferation due to size, weight, power consumption, and cost. In this work, we propose and experimentally demonstrate an on-chip tunable PT‐symmetric OEO. A tunable microwave photonic filter, a PT‐symmetric mode‐selective architecture, and two photodetectors are integrated on a silicon‐on‐insulator chip. By exploiting an on‐chip Mach–Zehnder interferometer to match the gain and loss of two mutually coupled optoelectronic loops, single‐mode oscillation can be obtained. In the experiment, the oscillation frequency of the on-chip tunable PT‐symmetric OEO can be tuned from 0 to 20 GHz. To emulate the integrated case, the OEO loop length is minimized, and no extra-long fiber is used in the experiment. When the oscillation frequency is 13.67 GHz, the single‐sideband phase noise at 10-kHz offset frequency is −80.96 dBc / Hz and the side mode suppression ratio is 46 dB. The proposed on-chip tunable PT‐symmetric OEO significantly reduces the footprint of the system and enhances mode selection.