Wide-field image correction of turbulence-induced phase requires tomographic reconstruction of each layer of turbulence. Before reconstruction can occur, the layers must be counted and ranged. A new signal-to-noise ratio metric for detecting a single layer of turbulence in a multi-layer atmosphere from SLOpe Detection And Ranging (SLODAR) measurements of Shack-Hartmann wave-front sensor (SHWFS) data is presented. 12,000 1-4 layer atmosphere profiles are procedurally defined by Fried length, layer altitude, and a minimum layer SNR requirement. Each profile is measured in simulation by a SHWFS in a 1.5 meter telescope with a 2.5 arcminute field of view over a 200 millisecond window. The simulation outputs are used as a 5-fold cross validation training data set for convolutional neural networks (CNNs) that count and range layers. The counting network achieved 92.6% accuracy and all ranging networks scored above 97.8% validation accuracy. We find that layers with SNR below 1 accounted for a majority of the misclassified points for all networks. We conclude that CNNs are a good candidate for wide-field image correction systems imaging through turbulence due to their ability to accurately profile the atmosphere from short time windows of collected data.
Complex-mask coronagraphs destructively interfere unwanted starlight with itself to enable direct imaging of exoplanets. This is accomplished using a focal plane mask (FPM); a FPM can be a simple occulter mask, or in the case of a complex-mask, is a multi-zoned device designed to phase-shift starlight over multiple wavelengths to create a deep achromatic null in the stellar point spread function. Creating these masks requires microfabrication techniques, yet many such methods remain largely unexplored in this context. We explore methods of fabrication of complex FPMs for a Phased-Induced Amplitude Apodization Complex-Mask Coronagraph (PIAACMC). Previous FPM fabrication efforts for PIAACMC have concentrated on mask manufacturability while modeling science yield, as well as assessing broadband wavelength operation. Moreover current fabrication efforts are concentrated on assessing coronagraph performance given a single approach. We present FPMs fabricated using several process paths, including deep reactive ion etching and focused ion beam etching using a silicon substrate. The characteristic size of the mask features is 5μm with depths ranging over 1μm. The masks are characterized for manufacturing quality using an optical interferometer and a scanning electron microscope. Initial testing is performed at the Subaru Extreme Adaptive Optics testbed, providing a baseline for future experiments to determine and improve coronagraph performance within fabrication tolerances.
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