Silicon Photonics-Based Heterodyne Interferometric Imager for Free-Space Imaging

This paper reports on the design, fabrication, and demonstration of a silicon photonics-based heterodyne interferometric imaging system. The photonic integrated circuit (PIC) can perform one-dimensional spectroscopy of unique input spectra using a single baseline within its 91 available baselines. The PIC uses polarization-diversifying gratings to separate incoming light into two distinct polarizations, an on-chip 2 × 4 optical hybrid, and a strong local oscillator (LO) to perform the heterodyne measurements. The optical hybrids combine the input signals with the LO and split them into two component pairs for phase-sensitive measurements. Furthermore, the PIC can perform 2D image reconstruction by combining many baseline pairs to measure the visibility of a simple target. These demonstrations show the PIC's capabilities for 1D spectroscopy and 2D imaging applications.