Describing light as ‘photons’ is of course just a model; QM is just a series of calculation procedures (algorithms), Schrödinger’s “Cat” paradox showed it to be self-contradictory, which remains unresolved, though fans of QM indulge in semantics (‘apparent’ paradox – see blog on The Cat and EPR Paradoxes).
A Cardiff physicist, Edmund Schluessel commented on the 2nd May post Light as Waves versus Quantum Mechanics of Photons
“The three concerns have all been dealt with within quantum mechanics long ago. In particular, the idea that the Maxwell equations are somehow incompatible with quantum mechanics is completely false. The Maxwell equations simply describe how the law of conservation of charge works in special relativity.”
This illustrates the way modern physics pedagogy has closed down thinking, as shown by Manjit Kumar’s Quantum (see Review). Let’s be more explicit on the second challenge, over QM describing photons as split when passing through a non-linear crystal: hν => hν1 + hν2, expressing conservation of energy and momentum with a similar relation between the wave vectors k.
Maxwellian treatment (SED theory) shows a second class of transformations hν => hν1 – hν2, corresponding to phase-matching relations. ‘Photon’ momentum and energy relations don’t hold in this class.
The Maxwellian prediction of this second class was validated in experimental studies in the reputable J. Optical Society of America in 2009 and 2010: as Wikipedia says, the
“experimental prediction of SED dubbed ‘spontaneous parametric up-conversion’ (SPUC) as a dual process to the well-known spontaneous parametric down-conversion (SPDC). SPUC was tested in 2009 and 2010 with positive results.”