High-dimensional adaptive optics techniques and applications

Thesis

Adaptive optics (AO) has traditionally been associated with feedback correction of phase aberrations. However, in practical imaging systems, performance is also significantly limited by coupled vectorial errors, including retardance and diattenuation. This thesis advances AO toward a high-dimensional framework that treats these error channels jointly. As a first step, this work develops and validates the vectorial extension of AO – pushing correction beyond scalar phase error – and establishes methods, metrics, and devices that pave the way to unified, highdimensional AO toolkit.

First, a vectorial adaptive optics (V-AO) correction module was implemented in a wide-field Stokes polarimetric microscope. Using a pupil-intensity feedback strategy, the system successfully compensated for spatially varying polarisation aberrations, improving the vectorial uniformity across the field of view from 77.1% to 91.2% and achieving a vectorial precision of over 95% across various samples.

Then the vectorial aberration correction concept is subsequently realised from the object’s perspective, hence termed as object-wise adaptive optics (O-AO). In this approach, a tunable arbitrary retarder array, realised by cascading polarisation modulators, is configured to form an inverse object for directly compensating retardance aberrations from the object’s perspective.

Following the investigation of retardance correction, the capability of V-AO to correct diattenuation aberrations in non-depolarising media is investigated. The correction performance is quantitatively assessed using advanced optical skyrmionic beams as indicators.

Finally, I study the correctability limit of V-AO in the presence of diattenuation in non-depolarising media. The correction performance is assessed using optical skyrmion beams as sensitive indicators, and the role of intensity loss and detector noise is made explicit. For example, when the diattenuation is strong (extinction ratio 𝐸=3.36), some states fall below the detection threshold and become unrecoverable, whereas for a weaker diattenuation (𝐸=1.65) the Stokes field can be effectively restored.

A summary of this thesis and an outlook on future research directions is provided, focusing on further advancing high-dimensional AO methodology and expanding its applications to a broader range of practical optical systems

Authors: Ma, Y

• DOI: 10.5287/ora-6qvmoryjj
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English