This thesis aims to demonstrate how the achromatic nature and design flexibility of liquid-crystal optics can be used to improve high-contrast imaging instruments to facilitate detailed exoplanet... Show moreThis thesis aims to demonstrate how the achromatic nature and design flexibility of liquid-crystal optics can be used to improve high-contrast imaging instruments to facilitate detailed exoplanet characterization.Chapter 2 discusses the design, performance, and future development of the liquid-crystal vector-apodizing phase plate (vAPP) coronagraph, five of which have been installed in different instruments on current generation telescopes since 2016. In chapter 3 we use the achromatic nature of the vAPP in combination with the LBT/ALES integral field spectrograph to obtain the first ever thermal infrared spectrum of the inner three HR 8799 planets. In Chapter 4 and 8 we show that by combining multiple grating patterns to reduce the influence of polarization leakage, we can improve the performance of liquid-crystal coronagraphs. In Chapter 5 and 6 we enhance sparse aperture masking, capable of detecting companions beyond the diffraction limit, by using liquid-crystal phase masks to enable low-resolution spectroscopy and improve throughput. In Chapter 7 we demonstrate that a liquid-crystal Zernike wavefront sensor can accurately and efficiently measure phase and amplitude aberrations simultaneously, facilitating extreme contrasts. Together, the concepts presented in this thesis can be used to improve high-contrast imaging instruments of both ground-based and space-based observatories. Show less
This thesis describes the development and validation of new high-contrast imaging techniques, with the ultimate goal of enabling the next generation of instruments for ELT-class telescopes to... Show moreThis thesis describes the development and validation of new high-contrast imaging techniques, with the ultimate goal of enabling the next generation of instruments for ELT-class telescopes to directly image Earth-like extra-solar planets orbiting around nearby stars. In particular, we focus on developing new focal-plane wavefront sensing techniques and liquid crystal optics to achieve high-precision adaptive optics control which is capable of stabilising the entire instrument. We demonstrate that one such hybrid optical concept, the coronagraphic Modal Wavefront Sensor (cMWS), is capable of providing real-time, broadband (500-900 nm) control of non-common path aberrations during on-sky observation. We also demonstrate via both realistic simulations and laboratory testing that the focal-plane sensing technique of “Fast and Furious” phase diversity provides a robust, software-only solution to unforeseen, performance-limiting wavefront control issues such as the low-wind effect seen in the SPHERE instrument at the VLT. Lastly, we characterise the extinction profile of the VLT-SPHERE-IRDIS apodised Lyot coronagraph using observations of the minor planet Ceres, and use this to devise a calibration scheme which optimises the accuracy with which polarised signals from the innermost regions of protoplanetary disks may be retrieved. Show less
