Yes, that's the main way we produce entangled photons. You put in a photon; you get out two photons, each with half the energy. To follow conservation laws, they must have complementary values of things like polarization: if one is up-down polarized, the other must be left-right polarized.

Those values are linked: if you measure one, the other will have the opposite. You can tell that it's not just pre-set values by measuring at a 45 degree angle, so you get some up-down and some left-right in each measurement. Take a bunch of those, and you'll see that the expected correlation between your measurements follows what quantum mechanics predicts, and not classical mechanics.

It's usually done with beta barium borate. You can buy it at optical suppliers:

https://eksmaoptics.com/nonlinear-and-laser-crystals/nonline...