Principles of the Optical Maser (1963)
In this 1963 instructional film, Dr. C.G.B. Garrett of Bell Laboratories explains how the "optical maser" (later known as a "laser") works. Its intended audience, according to the AT&T archive, was college students. I'd add to that audience "all nerds with a free half hour," particularly those who want to know how a laser really works. For example, how do they generate a source of light that radiates in just one direction? What does this have to do with radio? Why are British researchers (like Dr. Garrett) simultaneously terrifying and utterly compelling? Is he hypnotizing us?
Sample quote: "The optical maser is a radically new device, which represents a significant step forward in our ability to generate light in a controlled way. ... it gives out light instead of radio waves. It can be used to generate a beam of light which is at the same time very powerful and highly coherent. Coherent means, very roughly, well-organized. We'll see what it means more precisely later." Yes we will, Dr. Garrett.