Parallel radio-frequency signal-processing unit based on mode multiplexed photonic integrated circuit.

We propose and demonstrate a monolithically integrated mode division multiplexing (MDM) photonic system for parallel radio-frequency (RF) signal processing using a silicon platform. Two independent lowpass integrated microwave photonic filters (IMPFs) are successfully demonstrated using the proposed scheme. Full integration of active and passive devices ensures small footprint and good performance for microwave photonic applications. The adoption of MDM extends the parallel processing capability of a single wavelength line. The first order transverse electric (TE ₁ ) and second order transverse electric (TE ₂ ) modes are utilized for two IMPFs, with minimum bandwidth 3.7 and 3.8 GHz, respectively. Furthermore, by elaborately controlling the micro-ring based mode convertors, the continuous tuning of bandwidth is achieved from 3.7 to 8 GHz for TE ₁ and 3.8 to 7.6 GHz for TE ₂ based IMPFs.