Bruno Fièque

Uncooled amorphous silicon TEC-less 1/4 VGA IRFPA with 25 μm pixel-pitch for high volume applications

The high level of accumulated expertise by ULIS and CEA/LETI on uncooled microbolometers made from an amorphous silicon layer enables ULIS to develop 384 x 288 (1/4 VGA) IRFPA format with 25 μm pixel-pitch designed for low end application. This detector has kept all the innovations developed on the full TV format ROIC (detector configuration by serial link, low power consumption or wide electrical dynamic range ...). The specific appeal of this unit lies in the miniaturization of the TEC-less (Thermo-Electric Cooler) package and its extremely light weight. The reduction of the pixel-pitch and the innovative package turn this array into a low cost product well adapted for mass production. We will present first the simple TEC-less operating mode which has been developed. The electro-optical characterization versus environmental temperature will be presented.

320x240 uncooled microbolometer 2D array for radiometric and process control applications

Uncooled infrared focal plane arrays are being developed for a wide range of thermal imaging applications. Developments are focused on the improvement of their sensitivity enabling the possibility to manufacture high performance radiometric devices with internal temperature stabilized shield to determine precisely the input infrared flux. We present the characterization of a new radiometric device obtained from 320 x 240 uncooled microbolometer array with f/1.4 aperture. This device is well adapted to radiometric or process control applications and moreover shows a high level of stability due to the internal temperature stabilized shield which prevents the detector from camera internal temperature shift artifacts.

Uncooled microbolometer detector: recent developments at Ulis

Uncooled infrared focal plane arrays are being developed for a wide range of thermal imaging applications. Fire-fighting, predictive maintenance. process control and thermography are a few of the industrial applications which could take benefit from uncooled infrared detector. Therefore, to answer these markets, a 35 μm pixel-pitch uncooled IR detector technology has been developed enabling high performance 160 x 120 and 384 x 288 arrays production. Besides a wide-band version from uncooled 320 x 240 / 45 μm array has been also developed in order to address process control and more precisely industrial furnaces control. The ULIS amorphous silicon technology is well adapted to manufacture low cost detector in mass production. After some brief microbolometer technological background, we present the characterization of 35 μm pixel-pitch detector as well as the wide-band 320 x 240 infrared focal plane arrays with a pixel pitch of 45 μm.

HgCdTe Detectors for Space and Science Imaging: General Issues and Latest Achievements

HgCdTe (MCT) is a very versatile material system for infrared (IR) detection, suitable for high performance detection in a wide range of applications and spectral ranges. Indeed, the ability to tailor the cutoff frequency as close as possible to the needs makes it a perfect candidate for high performance detection. Moreover, the high quality material available today, grown either by molecular beam epitaxy or liquid phase epitaxy, allows for very low dark currents at low temperatures, suitable for low flux detection applications such as science imaging. MCT has also demonstrated robustness to the aggressive environment of space and faces, therefore, a large demand for space applications. A satellite may stare at the earth, in which case detection usually involves a lot of photons, called a high flux scenario. Alternatively, a satellite may stare at outer space for science purposes, in which case the detected photon number is very low, leading to low flux scenarios. This latter case induces very strong constraints onto the detector: low dark current, low noise, (very) large focal plane arrays. The classical structure used to fulfill those requirements are usually p/n MCT photodiodes. This type of structure has been deeply investigated in our laboratory for different spectral bands, in collaboration with the CEA Astrophysics lab. However, another alternative may also be investigated with low excess noise: MCT n/p avalanche photodiodes (APD). This paper reviews the latest achievements obtained on this matter at DEFIR (LETI and Sofradir common laboratory) from the short wave infrared (SWIR) band detection for classical astronomical needs, to long wave infrared (LWIR) band for exoplanet transit spectroscopy, up to very long wave infrared (VLWIR) bands. The different available diode architectures (n/p VHg or p/n, or even APDs) are reviewed, including different available ROIC architectures for low flux detection.

Infrared ROIC for very low flux and very low noise applications

Sofradir is involved in the manufacturing of detectors which cover a large range of wavelengths in the infrared domain from SWIR up to VLWIR for different kind of applications. Thus, different types of ROIC architectures are needed to cover these various kind of applications and operating conditions. As a major player of the infrared market, Sofradir has developed numerous ROIC with architectures enabling to answer most of the infrared applications in tactical, commercial and space domains. Sofradir is now able to present a new detector (384x288 with a 15 μm pitch) especially designed for very low flux applications in the SWIR domain (as astronomy for example). This new ROIC has been developed with CNES support and includes a SFD (Source Follower per Detectors) input stage enabling to achieve a high gain as well as a low readout noise and a vey low power consumption. In this paper, we will describe the architecture and functionalities of this new detector. Then, electro-optical characterizations and results will be described. Finally, main applications of this kind of detectors will be presented.

MWIR uncooled microbolometer: a way to increase the number of applications

Uncooled infrared focal plane arrays are being developed for a wide range of thermal imaging applications. ULIS now offers a new type of detector for middle and long wave applications. This detector has been designed from the standard product using the same focal plane array and the same package, only the window is different in terms of spectral transmission. This device is well adapted to high temperature measurements, special industrial processes and gas detection. After some brief microbolometer technological background, we will present the interest for such detectors by comparing LWIR/MWIR detector signal to noise ratio, we will then determine the advantages for different applications. Finally, we will describe and give the main EO characteristics and performances of this Ulis product.

Sofradir detectors for hyperspectral applications from visible up to VLWIR

Sofradir is involved in the manufacturing of the detector for PRISMA mission. Thanks to this experience, Sofradir has extended its Visible-Near infrared technology, called VISIR. This technology has the huge advantage to enable detection in both visible range and SWIR detection range (0.4μm up to 2.5μm). This 1000x256 array has been especially developed and dedicated for hyperspectral application. MCT Technologies at Sofradir covers also MWIR and LWIR infrared ranges for many years. Detectors for space applications have been already developed and validated and are currently running. For example, 1000x256 or 500x256 arrays 30 μm pitch (called Saturn or Neptune detectors) have already been validated in terms of irradiation behavior, thermal cycling, and ageing. Sofradir is now able to present a large MWIR or LWIR 1016x440 array with a 25μpixel pitch. This detector is also dedicated to hyperspectral application. Thus, with this new detector, Sofradir covers infrared ranges from Visible to VLWIR. After a brief reminding of the current VISIR focal plane array [1], and latest results from this detector, we will present in this paper the 1016x440 new array. The architecture and functionalities of this 1016x440 array will be presented and also the proposed packaging for this detector. Then, main general required performances and previous electro-optical characterizations will be also described.

New Sofradir VISIR-SWIR large format detector for next generation space missions

For now more than 10 years, Sofradir is involved in SWIR detector manufacturing, developing and improving its SWIR detectors technology, leading to a mature technology that enables to address most of missions needs in term of performances, but also with respect to hard environmental constraints. SWIR detection range at Sofradir has been qualified for space applications thanks to various programs already run (APEX or Bepi-Colombo programs) or currently running (Sentinel 2, PRISMA mission). Recently, for PRISMA mission, Sofradir is extending its Visible-Near infra-red technology, called VISIR, to 1000x256 hyperspectral arrays. This technology has the huge advantage to enable detection in both visible range and SWIR detection range (0.4μm up to 2.5μm). As part of the development of large format infrared detectors, Sofradir has developed Jupiter 1280x1024, 15μm pixel pitch detector in mid 2000s and this detector is available at production level since the end of year 2000s. Based on the experiences acquired in SWIR and VISIR technologies as well as in the development of large format infrared detectors, since 2011, in the frame of an ESA program (named Next Generation Panchromatic detector), Sofradir is developing a new VISIR 1kx1k detector. This new detector has a format of 1024x1024 pixels with a 15 μm pixel pitch and it is adapted to spectral range from UV to SWIR domain. This development contains mainly two challenges: - the extension of the detector sensitivity down to UV spectral range - the development of a large format Readout Integrated Circuit (ROIC) with 15μm pixel pitch adapted to VISIR and SWIR spectral range involving in particular low input fluxes. In this paper, we will describe the architecture and functionalities of this new detector. The expected performances will be presented as well. Finally, main applications of this kind of detectors and expected spatial missions will be presented.

Development activities on NIR large format MCT detectors for astrophysics and space science at CEA and SOFRADIR

CEA and SOFRADIR have been manufacturing and characterizing near infrared detectors in the frame of ESAs near infrared large format sensor array roadmap to develop a 2Kx2K large format low flux low noise device for space applications such as astrophysics. These detectors use HgCdTe as the absorbing material and p/n diode technology. The technological developments (photovoltaic technology, readout circuit, ...) are shared between CEA/LETI and SOFRADIR, both in Grenoble, while most of the performances are evaluated at CEA/IRFU in Saclay where a dedicated test facility has been developed, in particular to measure very low dark currents. The paper will present the current status of these developments at the end of ESAs NIRLFSA phase 2. The performances of the latest batch of devices meet or are very close to all the requirements (quantum efficiency, dark current, cross talk, readout noise, ...) even though a glow induced by the ROIC prevents the accurate measurement of the dark current. The current devices are fairly small, 640x512 15μm pixels, and the next phase of activity will target the development of a full size 2Kx2K detector. From the design and development, to the manufacturing and finally the testing, that type of detector requests a high level of mastering. An appropriate manufacturing and process chain compatible with such a size is needed at industrial level and results obtained with CEA technology coupled with Sofradir industrial experience and work on large dimension detector allow French actors to be confident to address this type of future missions.

CNES detector development for scientific space missions: status and roadmap for infrared detectors

CNES (French Space Agency) continuously drives the development of detectors for Space based Astronomy. Several promising infrared HgCdTe technologies are being developed at CEA and Sofradir. This paper gives a status on these developments as well as an overview of the associated roadmap.