Poor man's laser? [closed]

Would it be possible to use a non-laser light source to etch a flat surface? Using lenses or parabolic mirrors to focus the light to a point?

• Have you ever burned something with a magnifying glass on a sunny day? – Gilbert Apr 13 '19 at 22:43

Quantitatively if you hit your lens (or mirror) with a power $$P$$ and you manage to focus all the light in say an area $$a^2$$ (order less than 1 cm^2 for instance), then neglecting what happens to the air in the middle and the dilatation of the solid material you hit, the material receives a quantity of heat per unit of time equal to $$P$$.
Therefore at the beginning the temperature will rise as $$P/(\zeta a^2 \delta)$$ as time passes, where $$\zeta$$ is the specific heat capacity of the material and $$\delta$$ is the estimate of the thickness of the material you will have heated up when your definition of "beginning" ends. You should set a goal time (for instance you want to reach the goal temperature in 2 seconds) then make sure the heat can travel through the target material only by a small distance $$\delta$$, so that the change in the effective area of the "lit-up" portion is negligible ($$\delta^2\ll\delta$$ and you heat up a volume $$V=\delta(a+\delta)^2\sim a^2\delta$$).