A Can multiple layers of thin films increase infrared light absorption?

[hagopbul]

hello :

i have a small question , can we use multi layer thin films to increase absorption of infrared spectrum , on certain surface , ?

taking in mind that we use the same kind of thin film for each layer .
is that possible ?

best
hagop

 

[Cryo]

You can certainly increase absorption by using thin layers of different materials. What matters is change in refractive index. This is quite similar to anti-reflection coating, however you would have to use lossy optical materials for your anti-reflection coating to get absorption (as opposed to transmission)

 

[hagopbul]

What about x-rays

 

[Cryo]

In x-rays materials do not respond as effective media anymore, so the above approach will probably fail. Materials still scatter x-rays, so maybe one can try Anderson localization tricks, i.e. send x-rays at disordered media such as glass. Or simply use thicker layers. This is all on the level of a hypothesis, I do not work with x-rays.

 

[hagopbul]

But if the thickness of the thin-film is near the wave length of the x-ray incoming wave ?

 

[Cryo]

x-ray wavelength is on the scale of few Angstrom. Does it make sense to talk about electromagnetic media of such thickness? There is graphene and other 2d materials, but I would not call them electromagnetic media.

 

[hagopbul]

Multiple stack of thin films of that thickness

 

[Cryo]

Initially it was infrared, then x-ray, then single-wavelength thick layer, now many layers ... Is there anything specific you are after?

 

[hagopbul]

You answered the infra red question,then you indicated that single layer is not going to effect (the question of single layer was not clear my mistake) ,
But in case of multiple layers if they are thin enough that what I was wondering about or asking about

 

[Vagn]

You answered the infra red question,then you indicated that single layer is not going to effect (the question of single layer was not clear my mistake) ,
But in case of multiple layers if they are thin enough that what I was wondering about or asking about

Not particularly. Typically, for x-ray shielding bulk amounts of lead or other high atomic number materials, such as tungsten-filled polymers are used.
For infrared absorption the absorption process would typically be a band-to-band transition or the excitation of a vibrational/rotational mode.
As x-rays are much higher energy, different processes dominate (for instance the generation of secondary electrons and the subsequent bremsstrahlung). In principle, you can have high-absorption if the x-ray energy is at an absorption edge of the material in question, however you would still generate ionising radiation via Auger processes and bremsstrahlung.