The question of whether EM radiation can be treated as a classical EM wave or as a collection of photons is entirely dependent upon whether the number of photons collected in a measurment is large or small If its large then the classical treatment i e spectral radiance over infinitesimal frequency bands will apply Planck s law as stated in the article calls a spectral radiance which immediately implies a classical EM wave no reference needed Photonic emission is for any EM radiation where the number of photons collected is small including Planck s law in certain cases Broadband means the radiation is spread out over a relatively wide bandwidth narrowband means it is not Broadband is not necessarily photonic nor is narrowband necessarily classical EM Its not a matter of how spread out the radiation is its a matter of how many photons are collected in a measurement Broadband can be classical EM if many photons are collected narrowband can be photonic if only a few are collected