How do QWIPs work?

QWIP Technologies manufactures bound to quasi-bound QWIP detectors based on technology developed at the Jet Propulsion Laboratory.  QWIPs use quantum wells to detect photons. An incident photon enters the well and excites an electron from the ground state to the first excited state (see figure). In a bound to quasi-bound design, this first excited state lies at the edge of the conduction band. The QWIP is designed this way to yield high performance with low noise.

The QWIP well structure can be altered to change the central wavelength. QWIP Technologies has manufactured devices at a variety of MWIR and LWIR wavelengths. For details of how dark current and sensitivity vary with wavelength, please click here.

Due to quantum selection rules, QWIPs are not sensitive to normally incident light. Because of this, our QWIP designs use a grating to bend the light away from the normal. This grating structure is etched into the front of the QWIP FPA structure and the sensor illuminated from the back. The QWIP structure is bump bonded to a silicon read-out circuit so that we can measure the signal (see figure).

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