# Frequency doubler

> Red light through a doubler crystal — leftover red and a violet harmonic share the path onward.

![Frequency doubler](https://www.loomrume.com/optics/stills/frequency-doubler.png)

**Peter Franken** · 1961, University of Michigan — Nature letter

Franken, Hill, Peters and Weinreich put a ruby laser through quartz and looked for light at half the wavelength. The second-harmonic spot on the spectrograph plate was so faint the journal almost cropped it as dirt. The published figure still looks like a smudge with a caption.

That was the first optical second-harmonic generation: 694 nm in, a little 347 nm out. This bench keeps both on the path to the screen — leftover red and the violet that was not in the lamp.

## Sources

- [Second-harmonic generation](https://en.wikipedia.org/wiki/Second-harmonic_generation)
- [Peter Franken](https://en.wikipedia.org/wiki/Peter_Franken)

## Links

- [HTML](https://www.loomrume.com/examples/frequency-doubler)
- [Open in Studio](https://www.loomrume.com/experiments/new?template=frequency-doubler)
- [llms.txt](https://www.loomrume.com/llms.txt)