Photonic phase correctors based on grating couplers: proof of concept simulations and preliminary performance metrics

We report on simulations carried out for an integrated phase corrector that can efficiently couple the light distorted by atmospheric turbulence into a single-mode fiber (SMF). The photonic integrated circuit (PIC) consists of a square array of surface grating couplers used to deflect the off-plane wave vector of the free-space beamlets into the plane of a single-mode waveguide in the chip. Resistive elements acting as heaters are subsequently used to stretch a coiled section of the individual waveguides and, in doing so, shift the phase of the propagating modes. With the correct phase shifts applied to the channels — each corresponding to a subaperture on a telescope pupil — the channels can be coherently combined, and the collected light can be delivered to one output SMF. In an adaptive optics (AO) system, the phase corrector would act as a deformable mirror (DM) commanded by a controller that takes phase measurements from a wavefront sensor (WFS).