Quantum well infrared photodetector (QWIP) technology is an excellent solution for tactical applications due to the unmatched image uniformity, stability, and pixel operability (typically <99.9%). IRnova have a high-volume production of QWIP detectors in both QVGA and VGA formats since 1999. In 2017 a VGA format QWIP with 15 μm pitch was released, which has demonstrated excellent sensitivity (expressed as noise equivalent temperature difference (NETD)) of 30 mK at F/2 and 100 Hz frame rate. QWIPs also enable compact designs for polarimetric imaging by implementing polarization-sensitive lamellar gratings directly onto the detector pixels. Such polarimetric LWIR detectors (peak absorption at 8.5 μm) have been fabricated at IRnova as both QVGA and VGA format FPAs on 30 and 15 μm pitch, respectively. Polarimetric imaging with these detectors is demonstrated in this work, showing polarimetric contrast as high as 57±5 % for the QVGA format detectors, while the VGA format arrays provide enhanced spatial resolution at the expense of a lower polarization contrast (≈21±2 %). Finally, to meet the demand of highly sensitive and reliable HD LWIR detectors, a 1280×1024 QWIP detector on 10 μm pitch is the next targeted format of IRnova’s QWIP sensors. In this work, the anticipated performance of such detectors will be presented based on the simulation result using the in-house developed tools. The modelling takes into account the relevant ROIC parameters, as well as scaling of the detector performance with pixel size.
KEYWORDS: Quantum well infrared photodetectors, Sensors, Polarization, Staring arrays, Polarimetry, Sensor performance, Absorption, Modeling, Manufacturing, Signal to noise ratio
In this paper we demonstrate how the QWIPs are keeping all their promises in terms of performance, versatility and cost, partly thanks to excellent uniformity, stability and manufacturability, as well as the flexibility of tailoring both the detection wavelength and the polarization sensitivity.
Thanks to the intrinsic uniformity and stability of the III-V technology combined with the process maturity at IRnova, high resolution (VGA format, 15 µm pitch) QWIPs are now integrated in compact Integrated Detector Dewar Cooler Assemblies (IDDCAs). For regular high-end thermography applications, these IDDCAs operate with moderate 500 mW cryocoolers, which opens the field for handheld cameras.
Thanks to the band gap engineering, the detector’s spectral response can be tailored and optimized for different wavelength ranges. In addition to the 8.5 µm QWIP, which is optimized for thermal imaging, a QWIP with 10.5 µm peak wavelength has been tailored for detection of harmful gases, such as SF6. The performance of high resolution QWIPs with peak detection at 10.5 µm integrated in IDDCAs is demonstrated showing the impact of high sensitivity and high resolution on the image quality.
Thanks to the intrinsic sensitivity of QWIP to the polarization of the light it is possible to complement the thermal information with polarimetric information. This opens new possibilities for detection of certain features such as oil spill and de-camouflage. In this paper we demonstrate the high polarimetric contrast obtained with our 320×256 polarimetric IDDCA.
Continuing with its legacy of producing high performance infrared detectors, IRnova introduces its high resolution LWIR IDDCA (Integrated Detector Dewar Cooler assembly) based on QWIP (quantum well infrared photodetector) technology. The Focal Plane Array (FPA) has 640×512 pixels, with small (15μm) pixel pitch, and is based on the FLIRIndigo ISC0403 Readout Integrated Circuit (ROIC). The QWIP epitaxial structures are grown by metal-organic vapor phase epitaxy (MOVPE) at IRnova. Detector stability and response uniformity inherent to III/V based material will be demonstrated in terms of high performing detectors. Results showing low NETD at high frame rate will be presented. This makes it one of the first 15μm pitch QWIP based LWIR IDDCA commercially available on the market. High operability and stability of our other QWIP based products will also be shared.
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