Modular photochemical flow reactor system

A modular photochemical reactor system having a plurality of fluidic modules each having i) a central planar process fluid layer and ii) two outer planar thermal control fluid layers for containing flowing thermal control fluid and a plurality of illumination modules, the illumination modules of the plurality each having a planar form with first and second major surfaces and each having at least a first array of semiconductor emitters, the emitters positioned to emit from or through the first major surface, wherein the first array of semiconductor emitters has at least a first emitter and a second emitter, the first emitter capable of emitting at a first center wavelength and the second emitter capable of emitting at a second center wavelength, the first and second center wavelengths differing from each other.