We present a mechanistic framework to characterize photon absorption in quantum dots, enabling rational optimization of image sensor designs. Our analysis is based on the Analytic Path structured-field model, which treats both electrons and photons as extended electromagnetic structures rather than point particles. This resolves three critical issues: (1) the scale paradox—how nanoscale absorbers (10 nm) capture wavelength-scale photons (1500 nm), (2) the fragility problem—why purely magnetic coupling over hundreds of thousands of cycles cannot work in thermal environments, and (3) the mechanism gap—what physical process actually transfers energy. We identify three complementary absorption mechanisms: resonant antenna coupling, refractive index field concentration, and topological collapse via charge-spine intersection. The framework yields specific optimization strategies including magnetic doping for phase-locking enhancement, matrix rigidity requirements for coherence preservation, and refractive index engineering for field concentration. We provide testable predictions and material recommendations for next-generation SWIR sensors based on PbS and Ag_2Te colloidal quantum dots.