Complex Beam Mapping and Fourier Optics Analysis of a Wide-Field Microwave Kinetic Inductance Detector Camera

For astronomical instruments, accurate knowledge of the optical pointing and coupling is essential to characterize the alignment and performance of (sub-)systems prior to integration and deployment. Ideally, this requires the phase response of the optical system, which for direct (phase insensitive) detectors was not previously accessible. Here, we show development of the phase-sensitive complex beam pattern technique using a dual optical source heterodyne technique for a large-field-of-view microwave kinetic inductance detector camera at 350 GHz. We show here how you can analyze the measured data with Fourier optics, which allows integration into a telescope model to calculate the on-sky beam pattern and telescope aperture efficiency prior to deployment at a telescope.