<title>Adaptive optics at the University of Hawaii IV: a photon-counting curvature wavefront sensor</title>

Abstract

Understanding exoplanet formation and finding potentially habitable exoplanets is vital to an enhanced understanding of the universe. The use of nulling interferometry to strongly attenuate the central star's light provides the opportunity to see objects closer to the star than ever before. Given that exoplanets are usually warm, the 4 µm Mid-Infrared region is advantageous for such observations. The key performance parameters for a nulling interferometer are the extinction ratio it can attain and how well that is maintained across the operational bandwidth. Both parameters depend on the design and fabrication accuracy of the subcomponents and their wavelength dependence. Via detailed simulation it is shown in this paper that a planar chalcogenide photonic chip, consisting of three highly fabrication tolerant multimode interference couplers, can exceed an extinction ratio of 60 dB in double nulling operation and up to 40 dB for a single nulling operation across a wavelength window of 3.9 to 4.2 µm. This provides a beam combiner with sufficient performance, in theory, to image exoplanets.

The W. M. Keck Observatory Laser Guide Star Adaptive Optics System: Overview

“…Adaptive optics (AO) systems have been in use on astronomical telescopes since the early 1990s (Graves et al 1994;Rousset et al 1994;Rigaut et al 1998). From the beginning, astronomers recognized the limitations of AO due to the need to use relatively bright stars to measure the wave-front distortions introduced by Earth's atmosphere.…”