Widely Tunable Parity-Time-Symmetric Optoelectronic Oscillator Based on a Silicon Microdisk Resonator

A widely frequency-tunable parity-time (PT)-symmetric optoelectronic oscillator (OEO) based on a silicon microdisk resonator (MDR) is proposed and experimentally demonstrated. In the proposed OEO, two mutually coupled optoelectronic loops having an identical geometry with one having a gain and the other a loss, which are equal in magnitude, are implemented by employing the reciprocity of light propagation in an MDR, to form a PT-symmetric OEO. Thanks to the PT symmetry, single-frequency oscillation with low phase noise is implemented. The tuning of the frequency is realized by thermally tuning the MDR. The proposed OEO is demonstrated experimentally. A wide frequency tunable range from 2 to 12 GHz is realized. The phase noise is measured to be -105 dBc/Hz at a 10 kHz frequency offset, which can be further reduced if the loop length is increased.