Patent ID: 7291858

Claim:
A tunable quantum well infrared photodetector focal plane array (QWIP FPA) imaging device, comprising: one or more detector layers including asymmetnc quantum wells, each detector layer resides between contact layers and is coupled by barrier layers, thereby defining a stack of layers having a front side and a back side, wherein each detector layer has a spectrum of light absorption that changes in response to an applied bias, each of said asymmetric quantum wells being a unit cell comprising two quantum wells where a first undoped quantum well is configured to absorb a first spectrum, and a second doped quantum well is configured to absorb a second spectrum, wherein said second quantum well includes a well spike and a means for adjusting a ground state of said second quantum well using said well spike without affecting an excited state of said second quantum well, and wherein said means for adjusting is a bias signal; a light-coupling grating formed on the backside of the stack, the grating having a pattern that reflects a substantial portion of incoming light so as to disperse that light through the one or more of the detector layers, thereby facilitating absorption; and a reflective coating on sides of the detector layers so as to provide, in conjunction with the light-coupling grating, a photon-in-a-box configuration for containing light.