The photonic lantern wavefront sensor and imager: focal plane wavefront sensing and optimal imaging at the diffraction limit and beyond

Abstract

The use of a photonic lantern as focal plane wavefront sensor has seen recent widespread interest - it can remove non-common-path aberrations, accurately sense low-wind-effect and petal modes, and provide wavelength resolution. It encodes both the PSFs phase and amplitude into the intensities of its single-mode-fibre outputs, from which the wavefront is reconstructed (by neural network or other algorithm). It also offers exciting potential as an imager to resolve structure at and beyond the telescope diffraction limit, filling in a coronagraphs IWA blind spot. This can utilise interferometric techniques, or an oversampled photonic lantern, having sufficient measurement dimensions that the amplitude, phase and spatial coherence of the science field can be entirely constrained by the output fluxes, and so the wavefront-error-induced components can be disambiguated from the source spatial structure. Other applications such as fibre nulling, optimal single-mode fibre injection, spectroastrometry, and others are also in development. Here, a brief overview of the photonic lantern sensor and these various applications will be given, along with key references.