The unit of intensity or the irradiance of the light is $\mathrm{W/m^2}$. So what's the intensity of a light pointer?
Searching on the web, the laser pointer's power is about $5\mathrm{mW}$, imagine the spot is $1\mathrm{mm^2}$, then the power is about $5\mathrm{kW}/m^2$, the same magnitude as sunlight on earth.
I read a paper on floquet topological phase, the light intensity required is about $10^{17}\mathrm{W/m^2}$, I can't imagine how strong this light intensity is. Please give some real physical situation where this strong light intensity can occur.
I would assume this strong light intensity would "destroy" any material, is it true? If just shed the light for a femtosecond, I believe the material will still be OK.
Answer
The system with the greatest intensity I know of is at the National Ignition Facility. This generates a peak power of around 500TW and I think the target area is around 10 mm$^2$ (I can't find a detailed description of the target). That means the power density is around $5 \times 10^{19}$ Watts per square metre, but allow a factor of ten either side due to the uncertainty in the target size.
The effect of this high power density is to compress and heat deuterium and tritium until they undergo nuclear fusion.
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