Fig. 3: Diagram of the laboratory setup used for testing the photonic lantern wavefront sensor.

A collimated 685 nm laser (LASER) is passed through a linear polariser (POL) and via a fold mirror (MIR) onto a spatial light modulator (SLM), with a neutral density filter (ND) used to attenuate the beam. A wavefront constructed from a chosen set of Zernike terms is created by the SLM and focused to an image and injected by a microscope objective (L3) into the multimode end of the photonic lantern (PL). The intensity of the 19 outputs is then transmitted via multicore fibre (MCF) measured by a camera (CAM3) via lens L2. The raw PSF is also imaged via beamsplitter BS and lens L1 onto camera CAM1. The back-reflection off the fibre tip is imaged via the same beamsplitter and separate imaging system (L2, CAM2) to aid with alignment. Inset: illustration of the principle of the photonic lantern WFS. The incident aberrated wavefront is focused to an image at the focal plane, where the multimode end of the photonic lantern is placed. The complex wavefront determines the combination of modes excited within the multimode region, which are then translated via an adiabatic taper transition into an array of single-mode outputs, the intensities of which encode the complex wavefront information.