Quantum well infrared photodetectors (QWIPs) have many advantages in infrared detection, mainly due to the mature III-V material technology. The employment of the corrugated light-coupling scheme further improves the technology for its simplicity and efficiency. A C-QWIP enjoys the same flexibility as a detector with intrinsic normal incident absorption. In this chapter, we will discuss the sensitivity of C-QWIPs and their utilities in infrared detection, material characterization and electromagnetic modeling. Besides the standard corrugated structures, other exploratory detector architectures will also be described.