Adaptive optics with programmable Fourier-based wavefront sensors: a spatial light modulator approach to the LOOPS testbed

TL;DR

This paper introduces an upgraded adaptive optics testbed using a programmable Spatial Light Modulator to generate phase masks for Fourier-based wavefront sensors, enabling flexible testing of novel sensor concepts in real-time.

Contribution

It presents the integration of a SLM into the LOOPS testbed for dynamic phase mask generation, allowing flexible testing of Fourier-based wavefront sensors.

Findings

Successful generation of phase masks with the SLM

First closed-loop results with various wavefront sensors on the SLM

Demonstration of real-time adaptive optics correction

Abstract

Wavefront sensors encode phase information of an incoming wavefront into an intensity pattern that can be measured on a camera. Several kinds of wavefront sensors (WFS) are used in astronomical adaptive optics. Amongst them, Fourier-based wavefront sensors perform a filtering operation on the wavefront in the focal plane. The most well known example of a WFS of this kind is the Zernike wavefront sensor, and the pyramid wavefront sensor (PWFS) also belongs to this class. Based on this same principle, new WFSs can be proposed such as the n-faced pyramid (which ultimately becomes an axicone) or the flattened pyramid, depending on whether the image formation is incoherent or coherent. In order to test such novel concepts, the LOOPS adaptive optics testbed hosted at the Laboratoire d'Astrophysique de Marseille has been upgraded by adding a Spatial Light Modulator (SLM). This device, placed in a focal plane produces high-definition phase masks that mimic otherwise bulk optic devices. In this paper, we first present the optical design and upgrades made to the experimental setup of the LOOPS bench. Then, we focus on the generation of the phase masks with the SLM and the implications of having such a device in a focal plane. Finally, we present the first closed-loop results in either static or dynamic mode with different WFS applied on the SLM.