Variation on a Zernike wavefront sensor theme: optimal use of photons

Abstract

The Zernike wavefront sensor (ZWFS) is a concept belonging to the wide class Fourier-filtering wavefront sensor (FFWFS). The ZWFS is known for its extremely high sensitivity while having a low dynamic range, which makes it a unique sensor for second stage adaptive optics (AO) systems or quasi-static aberrations calibration sensor. This sensor is composed of a focal plane mask made of a phase shifting dot fully described by two parameters: its diameter and depth. In this letter, we aim to improve the performance of this sensor by changing the diameter of its phase shifting dot. We begin with a general theoretical framework providing an analytical description of the FFWFS properties, then we predict the expected ZWFS sensitivity for different configurations of dot diameters and depths. The analytical predictions are then validated with end-to-end simulations. From this, we propose a variation of the classical ZWFS shape which exhibits extremely appealing properties. We show that the ZWFS sensitivity can be optimized by modifying the dot diameter and even reach the optimal theoretical limit, with a trade-off for low spatial frequencies sensitivity. As an example, we show that a ZWFS with a 2λ/D dot diameter (where λ is the sensing wavelength and D the telescope diameter), hereafter called Z2WFS, exhibits a sensitivity twice higher than the classical 1.06λ/D ZWFS for all the phase spatial components except for tip-tilt modes. Furthermore, this gain in sensitivity does not impact the dynamic range of the sensor, and the Z2WFS exhibits a similar dynamical range as the classical 1.06λ/D ZWFS. This study opens the path to the conception of diameter-optimized ZWFS.

References in corpus (6)

• Limits of Adaptive Optics for high contrast imaging
• Calibration of quasi-static aberrations in exoplanet direct-imaging instruments with a Zernike phase-mask sensor
• Calibration of quasi-static aberrations in exoplanet direct-imaging instruments with a Zernike phase-mask sensor. III. On-sky validation in VLT/SPHERE
• General formalism for Fourier based Wave Front Sensing
• Kernel formalism applied to Fourier based wave front sensing in presence of residual phases
• Variation around a Pyramid theme: optical recombination and optimal use of photons

Cited by in corpus (13)

• Focal Plane Wavefront Sensing using Machine Learning: Performance of Convolutional Neural Networks compared to Fundamental Limits
• Non-modulated pyramid wavefront sensor: Use in sensing and correcting atmospheric turbulence
• Modeling noise propagation in Fourier-filtering wavefront sensing, fundamental limits and quantitative comparison
• Heimdallr, Baldr and Solarstein: designing the next generation of VLTI instruments in the Asgard suite
• Wavefront tolerances of space-based segmented telescopes at very high contrast: Experimental validation
• Into nonlinearity and beyond for Zernike-like wavefront sensors
• Optimizing Fourier-Filtering WFS to reach sensitivity close to the fundamental limit
• Experimental validation of active control of low-order aberrations with a Zernike sensor through a Lyot coronagraph
• Cascade adaptive optics with a second stage based on a Zernike wavefront sensor for exoplanet observations
• Adding colour to the Zernike wavefront sensor: Advantages of including multi-wavelength measurements for wavefront reconstruction
• Integrated coronagraphy and wavefront sensing with the PIAACMC
• Low-order wavefront control using a Zernike sensor through Lyot coronagraphs for exoplanet imaging
• Mid-order wavefront control for exoplanet imaging: preliminary characterization of the segmented deformable mirror and Zernike wavefront sensor on HiCAT