Metal tends to be opaque. However, if you perforate it with small holes in a certain pattern, it will still transmit some light—even if the holes are smaller than the wavelength of the light! This is known as extraordinary optical transmission (EOT), which has found uses in a number of devices since its discovery in the 1990s. However, a full understanding of the phenomenon has proven elusive. (That’s such a journalist way to put it, ain’t it?) A new experiment may have shown that the transmission is driven by two separate wave effects, and sorted out the role each plays in EOT.
Ordinarily, light can pass through an opaque barrier only if the barrier is pierced with openings larger than the light’s wavelength. (This also applies to all manner of waves, including sound and water waves.) That’s why EOT is fascinating: the holes are smaller than the wavelength, yet a substantial amount of light still gets through something that would ordinarily be opaque. Oddly, making the material thinner—and therefore more transparent—decreases the EOT effect. [Read more….]