Fig. 4. Programmable spectral response and spectroscopy demonstration.

a Exemplary spectral responsivities. The shaded areas represent the desired responses, while the corresponding lines depict the best achievable least-squares approximations obtained through linear combinations of the spectral responsivities in Fig. 3b. The numbers indicate the contributions a_i of the individual detector segments. The first three spectra in the figures correspond to widely-used fluorescent dyes (fluorescein, azadioxatriangulenium (ADOTA), dimethylquinacridone (DMQA)), while the remaining spectra illustrate some generic examples. b Optical spectra p = α₁u₁ + α₂u₂ used in experiments, shown here for α₁ = α₂ = 1. c Optimal spectral responsivity r (black line) and its approximation r′ in our photodetector (red line). d I_ph when α₂ is varied between 0 and 1, and α₁ = 1 is kept constant. e, I_ph when α₁ is varied between 0 and 1, and α₂ = 0 or 1.