How can you change the wavelength of UV light to visible or IR?

Answer 1

In a rough
1. Capture the UV signal by using a UV detector(s)
2. Sample the signal digitally or modulate using analog circuitry
3. Demodulate the signal by scaling the frequency down.
4. Convert the demodulated signal trough emitter into visible or IR

Answer 2

Well you can do what he said, but it also happens naturally. Because space is expanding always expanding it streches the wavelengths, so UV rays near the edge of visible light can get streched out into visible blue light. And that goes for the whole specturm. But understand this strech is minimal.

According to the Theory of Reletivity gravity causes space to contract so rays in a strong gravitaional field can cause its wavelengths to get closer shifting IR to visble. This is theory though. I believe the amount of gravity required is close to that of a blackhole so it would trap the light form being seen from an outside obsever. Nonetheless if you were inside the event horizon of the blackhole(and able to live and make time move foward(because time stops inside a blackhole for objects of mass) then you would be able to see the IR light that shifted to visible)