SIlicon Optomechanical optoellectronic Microwave Oscillator

High-quality microwave sources are required in multiple applications (radar, wireless networks, satellites, etc.). Typically, low-noise microwave oscillators are made by applying frequency multiplication to an electronic source. This requires a cascade of frequency-doubling stages, which strongly reduces the power of the final signal. Recently, different techniques to produce microwave tones via optical means have been proposed. The resulting device is an optoelectronic oscillator (OEO), with many advantages with respect to its electronic counterparts (immunity to EM interference, low weight, compactness, long-distance transport, etc). In the FET-Open project PHENOMEN, partner UPV designed and demonstrated a novel optomechanical cavity on a silicon chip displaying, for the first time, a localized mechanical mode at frequencies around 4 GHz within a full phononic bandgap and with a large OM coupling rate. By pumping the cavity with a blue-detuned laser, a high-Q microwave tone at f = 3.874 GHz is created at driving power of the order of 1mW. The noise figure of this OEO becomes as low as -101 dBc/Hz at 100 kHz, which is a remarkable good value for an OEO oscillating at GHz frequencies without any feedback mechanism. In addition, stronger pumping of the cavity enables the generation of multiple harmonics, thus reaching microwave frequencies above 10 GHz. Therefore, with the advantages of extreme compactness and Silicon-technology compatibility, this approach is a very promising candidate to build ultraweight OEOs, highly appropriate for space applications. Notably, the use of photonic technologies in space is one of the main activities of partner DAS. SIOMO aims at turning a silicon-photonics optoelectronic oscillator based on cavity optomechanics - recently demonstrated in the FET-Open project PHENOMEN by partner UPV - into a genuine economic innovation by addressing its technological transfer to the space sector via partner DAS.