Nicol prism
Concise Oxford English Dictionary © 2008 Oxford University Press:
Nicol prism /ˈnɪk(ə)l/
▶noun a prism for producing plane-polarized light, consisting of two pieces of optically clear calcite cemented together with Canada balsam.
– origin C19: named after the Scottish physicist William Nicol.
'Nicol prism' also found in these Oxford entries:

