Source Wavefront Generation for a Non-Interferometric Reconfigurable Null Test using a Photonic Lantern

A method is presented to use a fiber-optic device known as a photonic lantern to generate a reconfigurable custom wavefront for a null test of spherical, aspheric, and freeform optical surfaces. By modulating input intensity and phases at single mode fiber input ports, the wavefront of the output light field from the multimode end can be controlled to generate a custom nulling phase function. Generation of a desired wavefront is demonstrated by simulating a nineteen-port non-mode-selective photonic lantern. Using a linear response-matrix approach, a phase function with an RMS error of 44 nm from the target was generated in simulation. A compact form-factor noninterferometric null test for freeform optical surfaces is then described utilizing the photonic lantern as both a reconfigurable nulling source and a wavefront sensor.