Fig. 4: Near-field image of the photonic lantern’s multimode end face.

The dotted line marks the outer extent of the fibre core, which has radius of ~3 λ/D. a The lantern is back-illuminated by injecting light into the multi-core outputs (with random intensity distribution), exciting some combination of the fibre’s modes, visible here. b Back-reflected image of the multimode fibre when no aberrations are applied. c Back-reflected image of the multimode fibre when several aberrations are applied.