Silicon photonic spiral shape resonator applied to optoelectronic oscillator

We present here the implementation of an optoelectronic oscillator (OEO) that leverages the optical comb produced by a silicon add-drop ring resonator to directly convert signals from optical to microwave domain. The OEO comprises a CW laser, an intensity modulator, a silicon add-drop ring, a photodetector, and radiofrequency amplifier. By using millimeter-long silicon-on insulator micro-ring resonator, we generated an oscillation signal with a frequency determined by the free spectral range (FSR) of the ring. In this scheme, the sharp transmission peaks in the drop port of an add-drop silicon resonator are used as the optical comb. The optimised ring has a length of 5.8 mm with a measured FSR of 112 pm, an extinction ratio of 20 dB and an optical quality factor of 2.2 × 105. The complete OEO loop yields a 14.12 GHz signal with a phase noise level of −100 dBc/Hz at an offset of 100 kHz from the carrier. This result shows that OEOs directly based on millimeters long silicon rings are a promising path for generating low-noise microwave signals.