Compact Optical Beamforming Chip Using Broadband Continuously Tunable Delay Lines

In this work, we present a wideband 1 × 4 continuously tunable microwave photonic beamforming chip based on integrated optical switching delay lines (OSDLs) cascade with properly designed tunable asymmetry Mach-Zehnder interferometer (AMZI). Simulation and experiment were conducted to achieve over 25 GHz bandwidth continuously tunable delay (0 ps ∼ 3.54 ps), which can sufficiently cover a 5-bit silicon OSDL's discrete delay step (3.54 ps). Simulations on microwave photonic beamforming were also carried out. Additionally, to enhance the compactness of the microwave photonic beamforming chip, we introduce a non-invasive calibration method that eliminates the need for optical power monitoring tap after each optical switch, this approach can reduce the chip's footprint and optical I/O ports by approximately 50%.