Hi, I am not an expert in this topic but I have found the following discussion:

https://physics.stackexchange.com/questions/13851/can-you-split-a-photon

banach-tarski might help explain the parametric down conversion etc.

Santosh Sapkota This subject has been much discussed in the scientific community. In fact a photon that possesses certain energy can be absorbed and re-emitted with the same energy. One can also think that a photon after being re-emitted is divided into two with the same properties but each photon having half the energy of the original photon. Being that the total energy is conserved. Search the Delayed-choice Quantum Eraser experiment (DCQE) where by a nonlinear optical crystal BBO (beta barium borate) that converts the photon (from either slit) into two identical, orthogonally polarized entangled photons with 1/2 the frequency of the original photon. The paths followed by these orthogonally polarized photons are caused to diverge by the Glan–Thompson prism.

References:

https://www.quora.com/Can-photons-be-split-into-smaller-photons

https://en.wikipedia.org/wiki/Delayed-choice_quantum_eraser

It has been known and experimentally confirmed by Blackett and Occhialini as far back as 1933 that photons of energy 1.022 MeV or more can be destabilized into converting into pairs of massive electron-positron.

Very familiar in high energy accelerator circles.