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Weak gravitational lensing has emerged as a leading probe of the growth ofcosmic structure. However, the shear signal is very small and accuratemeasurement depends critically on our ability to understand how non-idealinstrumental effects affect astronomical images. WFIRST will fly a focal planecontaining 18 Teledyne H4RG-10 near infrared detector arrays, which presentdifferent instrument calibration challenges from previous weak lensingobservations. Previous work has shown that correlation functions of flat fieldimages are effective tools for disentangling linear and non-linear inter-pixelcapacitance (IPC) and the brighter-fatter effect (BFE). Here we present aFourier-domain treatment of the flat field correlations, which allows us toexpand the previous formalism to all orders in IPC, BFE, and classicalnon-linearity. We show that biases in simulated flat field analyses in Paper Iare greatly reduced through the use of this formalism. We then apply thisupdated formalism to flat field data from three WFIRST flight candidatedetectors, and explore the robustness to variations in the analysis. We findthat the BFE is present in all three detectors, and that its contribution tothe flat field correlations dominates over the non-linear IPC. The magnitude ofthe BFE is such that the effective area of a pixel is increased by$(3.54\pm0.03)\times 10^{-7}$ for every electron deposited in a neighboringpixel. We compare IPC maps from flat field autocorrelation measurements tothose obtained from the single pixel reset method and find a median differenceof 0.113%. After further diagnosis of this difference, we ascribe it largely toan additional source of cross-talk, the vertical trailing pixel effect, andrecommend further work to develop a model for this effect. These resultsrepresent a significant step toward calibration of the non-ideal effects inWFIRST detectors.

Brighter-fatter effect in near-infrared detectors -- III. Fourier-domain treatment of flat field correlations and application to WFIRST