Multilayer optics
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Multilayer optics are optical elements that use interference effects between thin layers of material. Optical coatings such as anti-reflective coatings found in high end binoculars and camera lenses are common examples. Scientific interference filters use diffraction and the wave properties of light to pass or reject narrow ranges of color.
In the EUV portion of the spectrum (wavelengths shorter than about 30 nm), nearly all materials absorb strongly, making it difficult to focus or otherwise manipulate light in this wavelength range. Telescopes such as TRACE or EIT that form images with EUV light use multilayer mirrors that are constructed of hundreds of alternating layers of a high-mass metal such as molybdenum or tungsten, and a low-mass spacer such as silicon, vacuum deposited onto a substrate such as glass. Each layer pair is designed to have a thickness equal to half the wavelength of light to be reflected. Constructive interference between scattered light from each layer causes the mirror to reflect EUV light of the desired wavelength as would a normal metal mirror in visible light. Using multilayer optics it is possible to reflect up to 50% of incident EUV light (at a particular wavelength chosen when the mirror is constructed).
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