Nicolas Dubost

PhD Student

The pupil-modulated point diffraction interferometer

Adaptive Optics -- Interferometry -- Wavefront Sensing

Current Research Summary:

Theoretical formulation and lab validation of a novel wavefront sensor (WFS) concept: the pupil-modulated Point Diffraction Interferometer (m-PDI). PDIs can perform direct wavefront sensing (as opposed to a Shack-Hartmann's or a pyramid's indirect sensing through gradients) with nano-metric accuracy, allowing them to tackle problems ranging from persistent speckle suppression in high-contrast imaging, to fine cophasing of segmented aperture telescopes and achieving eXtreme Adaptive Optics (XAO). One of the main advantages of the m-PDI over other interferometric approaches is its wide chromatic range for extended throughput. This property is currently being tested in the lab where the performance of the instrument with polychromatic light is proving to be comparable to the one with monochromatic light. A tip-tilt adaptive optics system is developed and successfully tested on telescope. The instrument is intended to improve the spatial resolution of the image. It is designed for visible band of the electromagnetic spectrum and has resolution of 0.08" with diffraction limited field of view (FOV) of 1.2’. To evaluate the performance of the instrument, it is tested on pair of stars that are separated by few arc-seconds (≈ 2") to several arc-seconds and of magnitude (mv) brighter than 6 in the visible band. The preliminary results have shown an ≈ 47% improvement in image resolution and slightly above 100% improvement in the peak intensity of the image over an integration time of 5 minutes. The instrument is tested for different correction loop frequencies over a field of view of ≈ 1.2" by observing a cluster of stars.

Prior Research:

Masters at PUC, Chile, until Juin 2015. Project: Turbulence estimation in wide-field adaptive optics systems