Thanks to their high technology readiness level, quantum well infrared photodetectors (QWIP) provide an efficient and swift solution for meeting the increased demand for advanced LWIR imaging systems. IRnova’s present portfolio includes QWIP detectors for LWIR dual-colour, gas detection, and polarimetric imaging on 30 and 15 μm pitch, while the development of large-format HD arrays on 10 μm pitch is ongoing.
In this work, the latest advancements for LWIR QWIP detectors (peak absorption at 8.5 μm) are presented: firstly, focusing on the progress on HD-format detectors on 10 μm pitch and secondly, presenting the enhanced polarization contrast in IRnova’s VGA-format polarimetric detector Fenrir (640×512 on 15 μm pitch). In the new Fenrir, the polarization contrast has increased from ~25% to ~40%, resulting in improved tracing of the polarimetric signatures as visualized by field tests. Furthermore, by employing array-wide pixel-level spectroscopy, excellent spatial uniformity across detector arrays has been confirmed.
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.
TiO2 nanoparticles dispersion was used to fabricate three dimensional (3D) composite structures on the surface of various substrate materials as well as on the surface of nitride light emitting diodes (LEDs). Optical power enhancements in the range of ~1.4-2.1 were measured.
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