Optical Direction-Finding Based on Silicon Photonic Integrated Circuits

In this paper, a high accuracy direction-finding (DF) system based on silicon photonic integrated circuits (PIC) is proposed. The accurate direction of a target can be determined by its position in the reconstructed image obtained by spatial frequency (SF) sampling and inverse Fourier transform according to theories of interferometric imaging. With the help of numerical simulation, we designed a multi-baseline structure which could significantly improve the accuracy and field of view (FOV) of DF system. To address the integration and stability problems which confine the application of DF techniques, we innovatively implemented our multi-baseline structure on Silicon-On-Insulator (SOI) platform. Thermal phase-shifters and multi-mode interferometers are employed for on-chip quadrature modulation detection. By testing the fabricated DF chip with a 1550 nm laser source at 14 different positions, we verified its DF accuracy and stability. The experimental results show excellent DF performance with an average angular error similar to 215.71 mu rad and prove the potential of our technique in high precision DF applications.