Non-modulated pyramid wavefront sensor: Use in sensing and correcting atmospheric turbulence

TL;DR

This paper introduces a new calibration method for the non-modulated pyramid wavefront sensor, enabling effective sensing and correction of atmospheric turbulence without the need for tip-tilt modulation, thus maximizing sensor sensitivity.

Contribution

The study presents a calibration approach that models the sensor response under residual turbulence, allowing non-modulated pyramid sensors to operate effectively in adaptive optics systems.

Findings

Calibration reduces model error in the interaction matrix.

Non-modulated pyramid sensors can sense and correct turbulence effectively.

The approach extends the operational conditions of the sensor.

Abstract

Context. The diffusion of adaptive optics systems in astronomical instrumentation for large ground-based telescopes is rapidly increasing and the pyramid wavefront sensor is replacing the Shack-Hartmann as the standard solution for single conjugate adaptive optics systems. The pyramid wavefront sensor is typically used with a tip-tilt modulation to increase the linearity range of the sensor, but the non-modulated case is interesting because it maximizes the sensor sensitivity. The latter case is generally avoided for the reduced linearity range that prevents robust operation in the presence of atmospheric turbulence. Aims. We aim to solve part of the issues of the non-modulated pyramid wavefront sensor by reducing the model error in the interaction matrix. We linearize the sensor response in the working conditions without extending the sensor linearity range. Methods. We developed a new calibration approach to model the response of pyramid wave front sensor in partial correction, whereby the working conditions in the presence of residual turbulence are considered. Results. We use in simulations to show how the new calibration approach allows for the pyramid wave front sensor without modulation to be used to sense and correct atmospheric turbulence and we discuss when this case is preferable over the modulated case.