On-sky results for the integrated microlens ring tip-tilt sensor

Abstract

We present the first on-sky results of the micro-lens ring tip-tilt (MLR-TT) sensor. This sensor utilizes a 3D printed micro-lens ring feeding six multi-mode fibers to sense misaligned light, allowing centroid reconstruction. A tip-tilt mirror allows the beam to be corrected, increasing the amount of light coupled into a centrally positioned single-mode (science) fiber. The sensor was tested with the iLocater acquisition camera at the Large Binocular Telescope in November 2019. The limit on the maximum achieved root mean square reconstruction accuracy was found to be 0.19 λ/D in both tip and tilt, of which approximately 50% of the power originates at frequencies below 10 Hz. We show the reconstruction accuracy is highly dependent on the estimated Strehl ratio and simulations support the assumption that residual adaptive optics aberrations are the main limit to the reconstruction accuracy. We conclude that this sensor is ideally suited to remove post-adaptive optics non-common path tip tilt residuals. We discuss the next steps for the concept development, including optimizations of the lens and fiber, tuning of the correction algorithm and selection of optimal science cases.

2023 Astrophotonics Roadmap: pathways to realizing multi-functional integrated astrophotonic instruments

“…Microlens-ring tip-tilt (MLR-TT) sensor. Reproduced with permission from [83] © The Optical Society. Integrated photonic instrument illustration by Phil Saunders.…”

A report on the status of astrophotonics for optical/IR interferometry and beyond

“…While the pupil plane can be sampled using photonic devices, the same can occur with the image plane of a telescope. I already mentioned here above the implementation of a photonic lantern in the image plane to serve as all-photonic wavefront sensor 30 , which shares a similar conceptual approach -although different in its implementation -to the micro-lens tip-tilt sensor of Hottinger et al 38 . In the area of telescope interfaces with image plane sampling/remapping, a promising result was recently published where a small portion of the extreme-AO corrected field-of-view with SCExAO on the 8-m Subaru telescope was sampled and remapped into a pseudoslit feeding a high-resolution spectrograph.…”