Dewar-cooler-integrated high sensitivity MWIR wave front sensor

Abstract

Recent developments in the Mid Wave InfraRed (MWIR) optical domain were made on materials, optical design and manufacturing. They answer increasing demands for more compact, less temperature dependent optical systems with increased optical performances and complexity (multi- or hyper- spectral imagery). At the same time, the characterization of these components has become strategic and requires solutions with higher performance. The optical quality of such devices is measured by wave front sensing techniques. PHASICS previously developed wave front sensors based on Quadri-Wave Lateral Shearing Interferometry (QWLSI) using broadband microbolometers cameras for infrared measurements. However they suffer from reduced light sensitivity in the MWIR domain, which limits their use with broadband sources such as black bodies. To meet metrology demands, we developed an innovative wave front sensor. This instrument combines the metrological qualities of QWLSI with the radiometric performances of a last generation detection block (Infrared Detector Dewar Cooler Assembly, IDDCA) with a quantum infrared focal plane array (IRFPA) of HgCdTe technology. The key component of QWLSI is a specific diffractive grating placed a few millimeters from the focal plane array. This requirement implies that this optics should be integrated inside the IDDCA. To achieve this, we take advantage of the experience acquired from recent developments with optics integrated in IDDCA. Thanks to this approach, we developed a high spatial resolution MWIR wave front sensor (160x128 points) with a high sensitivity for accurate measurements under low-flux conditions. This paper will present the instrument technological solutions, the development key steps and experimental results on various metrology applications.