In the field of electromagnetic sensing, certain sensing structures place strict requirements on the polarization of the electromagnetic radiation for absorption by the structure. To meet these requirements, a diffraction grating is used to convert the electromagnetic radiation into a polarization or mode which is absorbed by the sensing structure. The inclusion of a reflector in the sensor creates an electromagnetic cavity. When the incident radiation is at a frequency which resonates within the cavity, a standing wave results, creating regions of high and low electric field intensities. The magnitude of the detection signal is proportional to the number and magnitude of the high intensity field regions. The boundary conditions within the electromagnetic cavity have a significant impact on the magnitude of the detection signal. Improper boundary conditions cause the electromagnetic field to interfere destructively with itself, diminishing the number and magnitude of high field regions, especially near the periphery of the sensing structure.
One such electromagnetic sensor is the quantum well infrared photodetector (QWIP). With current objectives to develop large area focal plane array (FPA) technology for mid wave-length infrared radiation (MWIR), long wavelength infrared radiation (LWIR), and multi-spectral applications at low cost with high performance, QWIP technology is being extensively explored. QWIP technology suffers some performance disadvantage relative to other infrared (IR) technologies. In view of the more mature material and processing technology utilized with QWIP FPAs relative to other IR technologies, there exists a need for design improvements to enhance quantum efficiency (QE) and therefore performance.