Nicolette

Nicolette, an armoured guardian of light, raises a cut crystal and sends one clean beam out of it.

The Physics

In 1828 William Nicol of Edinburgh cut a calcite rhomb along a diagonal and cemented the halves back together with Canada balsam (Edinb. New Phil. J. 6, 83). Calcite splits light into an ordinary ray (n_o ≈ 1.658) and an extraordinary ray (n_e ≈ 1.486, along the slowest direction). Balsam sits between them at about 1.55. The ordinary ray, meeting the lower-index balsam at a steep angle, is totally internally reflected out of the side; the extraordinary ray passes. What leaves the end is linearly polarised.

n_o > n_balsam > n_e

• n_o: ordinary refractive index of calcite, ≈ 1.658
• n_balsam: Canada balsam, ≈ 1.55
• n_e: extraordinary index, ≈ 1.486 (sodium light)

It is a polariser by geometry, not an absorbing filter: the rejected ray is steered away, not soaked up.

Honest caveat: The extraordinary index varies with direction between 1.486 and 1.658, and the prism only works over a limited cone of entry angles.

On the sticker

Nicolette holds up a glowing crystal with a single cyan beam leaving it. Printed text: NICOLETTE with the line n(o) > 1.55 > n(e). Pixel-art kiss-cut vinyl sticker, white, in 2″, 3″, 4″ and 6″ sizes.