Quantum well infrared photodetectors for dual-band thermal imaging and two-photon detection


Quantum well infrared photodetectors for dual-band thermal imaging and two-photon detection

Schneider, H.

Quantum well infrared photodetectors (QWIPs) provide unique opportunities for high-performance thermal imaging. Due to their narrow absorption bands with relative spectral widths of the order of 10%, QWIPs are particularly suitable for thermal imaging applications involving several atmospheric transmission bands or several colors within the same band. For dual-band/dual-color FPAs, QWIP technology has the unique property that the active region for the long-wavelength band is transparent for the short-wavelength band. Narrow intersubband transition linewidths also enable us to enhance resonantly the cross section for two-photon-absorption by several orders of magnitude. This approach results in particularly sensitive quadratic two-photon detectors, which are useful for pulse diagnostics and photon correlation measurements of mid-infrared laser sources. In the first part of this talk, I will report on QWIP structures optimized for thermal imaging applications and on the performance of QWIP thermal imagers which were jointly realized by the Fraunhofer-Institute for Applied Solid State Physics (Freiburg, Germany) and AIM Infrarot-Module GmbH (Heilbronn, Germany). In particular, a dual-band QWIP FPA with 384x288 pixels detecting simultaneously in the 8 – 12 µm long-wavelength infrared (LWIR) and 3 – 5 µm mid-wavelength infrared (MWIR) regimes was found to exhibit a noise-equivalent temperature difference as low as 20.6 mK in the LWIR and 26.7 mK in the MWIR spectral bands. The array, which is based on a photoconductive QWIP for the MWIR and a photovoltaic "low-noise" QWIP for the LWIR, allows for synchronous and pixel-registered image acquisition in both bands. This functionality yields several advantages, including better distinction between target and background clutter, operation in a much wider range of ambient conditions, and the ability of remote absolute temperature measurement. The second part of my talk will address quadratic detection involving two-photon transitions in specially designed QWIP structures. These two-photon QWIPs are exploited in autocorrelation measurements of pulsed infrared sources including the free-electron laser FELBE in Dresden.

Keywords: quantum well infrared photodetector; dual-band QWIP focal plane array; intersubband transition; two-photon detection; quadratic autocorrelation

  • Invited lecture (Conferences)
    3rd International Symposium on Photoelectronic Detection and Imaging (ISPDI 2009), 17.-19.06.2009, Beijing, China

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Publ.-Id: 12909