The characteristics of an oppositely placed double potential barrier photodetector structure were investigated under longitudinal illumination. The functional abilities of the silicon n+-p-n+ structure were studied under longitudinal illumination. The choice of impurity concentration in the n+- and p- regions provided the difference in heights of the potential barriers near-surface, rear, and oppositely directed regions and their conjoining in the high-resistance p-base. The widths of the depletion regions of these barriers varied with a step change in the bias voltage. The redistribution of the fraction of absorption of electromagnetic waves between the barriers and the change in their contribution to the total photocurrent was investigated. In connection with this, short-wavelength (490 nm) and long-wavelength (830 nm) spectral maxima were formed. In the voltage range commensurate with the difference in the heights of the potential barriers, the inversion of the sign of the spectral photocurrent and, using the developed algorithm, the spectral distribution of the absorbed radiation intensity, were obtained. A physical explanation of these results is provided. The structure under investigation enables the selective registration of individual waves and their intensities. The results reported here enable an optimistic spectrophotometric outlook for oppositely placed double-barrier photonic structures.