Someone was asking me about trigering fusion with this, and i think fusion at the core of the sun is at millions °C, and at the surface you get 5500°C, so beacuse photons carry entropy and the photons of the surface is what you see, you will never be hotter than the surface of the sun, even as much rays you can concentrate. It is not a mather of how much rays you get but of pure entropy. Hotter means more entropy. You can not create more entropy in this case.

Please someone correct me if im wrong.