Large, Wafer-Thin Optical Apertures Leveraging Photonic Integrated Circuits to Replace Telescopes for Communications

Large, Wafer-Thin Optical Apertures Leveraging Photonic Integrated Circuits to Replace Telescopes for Communications

Utah State University, Logan, UT

To aid in driving down the size, weight, and power (SWaP) of space-based optical communications terminals, we present a large-aperture telescope-replacement technology that reshapes a beam from a single-mode fiber to ~5 cm and larger apertures on a silicon wafer by using photonic integrated circuit (PIC) components. We achieve multi-centimeter apertures by sacrificing wide-angle steering in favor of good beam quality and manageable controls. Light from a single-mode fiber is coupled to a silicon chip consisting of low-loss silicon nitride waveguides for signal distribution to large phase-controlled emitters. Our demonstrations of beam phasing across a 1.8-cm-diameter, 16-emitter phased array show excellent agreement with simulations. We have designed and simulated a 4.7 cm, 64-emitter array and have begun fabrication as of 2023. This architecture removes the need for beam expansion optics, free-space propagation for beam expansion, and the support structure and housing used in traditional telescope assemblies. Its low size and weight make it compatible with current and future beam steering mechanisms, and its reduced loading provides added potential for size and weight reductions in those subsystems. We believe the architecture can eventually be expanded to larger apertures of 10 cm or more without significantly increasing thickness.