Calibration techniques for high angular resolution measurement with photonic lanterns on Subaru/SCExAO

Achieving high angular resolution in the visible and near-infrared is crucial for many subfields of astronomy. However, imaging resolution is typically limited to lambda/D for a single telescope. Recently, the use of photonic lanterns (PLs) for high angular resolution applications has gained interest due to their potential for super-resolution (sub-diffraction limit) capabilities. A PL can be used as a high-throughput compact integral field unit (IFU) when its single-mode outputs are fed into a diffraction-limited spectrograph. However, the sensitivity of the PLs to small angular scales makes them susceptible not only to the astronomical scene but also to static and time-varying wavefront errors, necessitating dedicated observation strategies and post-processing techniques for calibration. We present lessons learned with on-sky tests with a three-port infrared PL and a 19-port visible PL installed on the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) testbed at the Subaru Telescope, isolating spatially resolved astronomical signals from wavefront errors using spectral-differential techniques and reconstructing spectral-differential images.