Terahertz Mirrors, Reflectivity of metals for THz radiation

Terahertz (THz), T waves, or sub millimeter radiation, is currently finding more and more applications. The controversial full body scanners at airports that can “see through clothes” are based on T Waves.

Less publicised is the use of  THz radiation for medical imaging, chemical analysis, and for production quality control; “seeing” through cardboard packaging for example.

Absolute reflectance standards have yet to be developed for these wavelengths, but in the range 0.2 – 3.0 THz the reflectivity of Gold is reported as 99% (M Naftaly et al, Applied Optics, Vol 50, No. 19, 2011).

The thickness of the metal reflective surface should be at least twice the “skin depth” at that wavelength. That’s around 2.5nm at visible wavelengths (600THz), and 65nm at 1Thz. Laser Beam Products’ Gold coated mirrors have Gold thickness many times this minimum value.

It does mean that users of  THz radiation can confidently specify Gold coated metal mirrors, probably our Gold coating made onto all Aluminum mirrors. The facility to engineer tapped holes, dowel pins, O ring grooves and datum surfaces makes mounting and aligning all metal mirrors cheaper and easier.

See Laser Beam Products web page on Gold mirror coating 

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