A coherent camera system performs ranging, spectroscopy, and thermal imaging. Local oscillator radiation is combined with target scene radiation to enable heterodyne detection by the coherent camera's two-dimensional photodetector array. Versatility enables deployment of the system in either a passive mode (where no laser energy is actively transmitted toward the target scene) or an active mode (where a transmitting laser is used to actively illuminate the target scene). The two-dimensional photodetector array eliminates the need to mechanically scan the detector. Each element of the photodetector array produces an intermediate frequency signal that is amplified, filtered, and rectified by the coherent camera's integrated circuitry. By spectroscopic examination of the frequency components of each pixel of the detector array, a high-resolution, three-dimensional or holographic image of the target scene is produced for applications such as air pollution studies, atmospheric disturbance monitoring, and military weapons targeting.

Method and apparatus for coherent imaging of infrared energy

Suppression of non-radiative processes in semiconductor mid-infrared emitters and detectors

New trends in infrared detector technology

Lateral photodetectors with Ge quantum dots in Si

We study theoretically the conditions for achieving lasing action at infrared and far-infrared wavelengths based on intersubband transitions in semiconductor quantum well structures, taking into account resonant tunnelling and intersubband absorption-emission processes. Analysis of optical losses in the semiconductor quantum well structures reveals that a reasonably low threshold current density in the range of 1-5 kA cm-2 is achievable for room temperature lasing at emission wavelength of lambda =60 mu m. A significantly higher threshold current density of 40-50 kA cm-2 is required for lasing at lambda =10 mu m.

https://iopscience.iop.org/article/10.1088/0268-1242/9/6/005/pdf

Threshold current density calculations for far-infrared semiconductor lasers

The author presents a detailed study of a wide variety of quantum well infrared photodetectors, which were chosen to have large differences in their optical and transport properties. Intersubband transitions based on photoexcitation from bound-to-bound, bound-to-quasicontinuum and bound-to-continuum quantum well states were investigated. The measurements and theoretical analysis included optical absorption, responsivity, dark current, current noise, optical gain, hot-carrier mean free path, net quantum efficiency, quantum well escape probability, quantum well escape time, as well as detectivity.

https://iopscience.iop.org/article/10.1088/0268-1242/8/1S/089/pdf

B F Levine

Papers

Device physics of quantum well infrared photodetectors