IQ Photonic Receiver for Coherent Imaging with a Scalable Aperture

Abstract

Silicon photonics (SiP) integrated coherent image sensors offer higher sensitivity and improved range-resolutionproduct compared to direct detection image sensors such as CCD and CMOS devices. Previous generation of SiP coherent imagers suffer from relative optical phase fluctuations between the signal and reference paths, which results in random phase and amplitude fluctuations in the output signal. This limitation negatively impacts the SNR and signal acquisition times. Here we present a coherent imager system that suppresses the optical carrier signal and removes non-idealities from the relative optical path using a photonic in-phase (I) and quadrature (Q) receiver via a 90 • hybrid detector. Furthermore, we incorporate rowcolumn read-out and row-column addressing schemes to address the electro-optical interconnect density challenge. Our novel rowcolumn read-out architecture for the sensor array requires only 2N interconnects for N 2 sensors. An 8 × 8 IQ sensor array is presented as a proof-of-concept demonstration with 1.2 × 10 −5 resolution over range accuracy. Free-space FMCW ranging with 250 µm resolution at 1 m distance has been demonstrated using this sensor array.

Achieving full grating-lobe-free field of view with low-complexity co-prime photonic beamforming transceivers

“…In addition, heterodyne receiver measurements are more susceptible to noise. This is not a fundamental limitation of the proposed co-prime transceiver, and more complex receiver architectures such as in-phase and quadrature (IQ) receivers [27] can better suppress the undesired noise fluctuation in the received signal.…”