The other day I was thinking about the wire mesh cover used in microwaves to keep the microwave radiation inside cooking your food. The idea is that the spacing of the mesh is much smaller than the wavelength of light used for microwave ovens (typically 120mm, compared to the mm size mesh).
This has gotten me thinking, in cryogenic applications you typically have to use shielding to block out thermal blackbody radiation. Usually you have an object at Liquid helium temperatures or below (<10 Kelvin), and are fighting off radiation from ambient temperature objects (300 Kelvin). Converting 300 Kelvin to a wavelength of light using $k_B T = \hbar \omega$, we are talking about 50 micrometer wavelengths. So if we wanted a grid to block that out, we would consider a mesh with a spacing of about ten times smaller, or 5 micrometers.
Does this mean that rather than a bulk radiation shield, we could use a fine mesh grid to block thermal radiation? I imagine this would be pretty useful in the context of Vis/UV/X-ray detectors where you could allow line of sight detection while also blocking out thermal radiation which may mess up the detector. On the other hand, most applications wouldn't need this complication, but surely some experiments would benefit from it.
My question is: has such a design ever worked in practice? If so, can you provide a citation? If not, was the limiting factor the physics itself, or an engineering problem?
