Optical functions integrated onto a mid-wave infrared dectector

In the past century, optical functions were integrated onto the visible detectors. Nowadays, most of the visible detectors used for imagery are characterized by a large format, a small pixel pitch and RGB (Red-Green-Blue) filters. In the infrared bands of interest, the mid-wave infrared range (MWIR) can be divided in two sub-bands. The wavelengths associated to the MWIR blue band are ranging from 3.0 up to 4.2 μm and the red band from 4.2 up to 5.1μm. LYNRED and Safran Reosc are developing a new technological brick to integrate two optical functions onto a MWIR focal plane array. The objective of these optical functions is to increase the accuracy of detection minimizing the false alarms. These optical functions are realized onto the FPA like a chess board. On the one hand, half of the pixels are using an antireflective coating. On the other hand, the other pixels are filtered with a high pass filter. As a consequence, the first type of pixels has the ability to detect photons in the entire MW spectral range whereas the others are able to detect in the red band only. A first demonstrator has been realized using this new concept associated to a HgCdTe MW infrared detector. The performances are very promising with very low NETD (below 20mK) in both bands and a spectral crosstalk per pixel of 7.7%. A high operability has been demonstrated in both bands (> 99.5%). The reliability of this technological solution has been evaluated with success. Based on the heritage of Daphnis, a 10μm pitch product, LYNRED envisions a new one using this dual-color technological brick like an add-on onto the FPA. Thanks to the outstanding Modulation Transfer Function performance of the Daphnis, and a specific design of the micro-pattern structure of the filters, the spectral performances should significantly be improved.