I want to take a focused beam of light from the sun, fire it into a ball that consists of many layers of 2 way mirror and a clear polymer. The mirror layers reflect most of the light on one side. That must be facing the center of the sphere.
The center will have particulates that convert the light to heat.
My hypothesis is that light will be statistically likely to migrate to the center. It will eventually hit the particulates converting to heat. Different wavelengths will be absorbed while others will be reflected to converge with the center again.
This device carries no risk of explosion. Any temperature increase past 300C and the layers of mirrors fail. Releasing large amounts of light and effectively killing the device.
Now I just need money and a team.