Flexible Millimeter-Wave Carrier Generation up to the Sub-THz with Silicon Photonics Filters

We report on the characterization of a photonic integrated circuit (PIC) for the generation of a RF carrier wave in the millimeter-wave band up to the sub-THz region. The circuit has been implemented in silicon waveguides through a standard multi project wafer service, and exploits an innovative filtering technique for effectively selecting two tones out of an input optical frequency comb (OFC) driven by a local oscillator at a sub-multiple frequency of the system output RF signal. Experimental results confirm a large suppression ratio of RF spurious tones up to more than 30 dB for generated carrier frequencies ranging from 20 GHz to 126 GHz with input OFC frequency spacing between 10 GHz and 20 GHz. Additionally, the unfiltered input OFC tones are recovered in the scheme with negligible loss, enabling efficient comb reuse for minimizing optical and RF equipment in PIC-based future wireless communications and sensing networks systems. Design strategies for further improving the circuit performances are finally presented.