"works with wavelengths of light ranging from about 1 to 18 gigahertz"

frequency is in hertz.
wavelength is a length, so it will be in meters or feet or inches or volkswagen bugs.

that is all. </pedantic>

Nice article! I thought it was an interesting way to bring a qualitative feel back into software development. In a word of mathematics and code, we often lose sight of those qualitative things in favour of hard numbers. I think developers too often live in the analytical world like european Chess when they should be combining intuition with analysis like in Go / Weiqi.