by PhilipJ on 18 February 2008
Celebrating 50 years of the journal Physical Review Letters, the editors at PRL have begun collecting hightlights of the past 50 years. They’re only a few years into things, but there’s already a paper that caught my eye: Generation of Optical Harmonics by Franken et al., PRL 7, 118 (1961) (link, seemingly freely accessible).
Shortly after the invention of the ruby laser (and before that the maser), it was discovered that a harmonic of the laser’s natural frequency was being emitted from dielectrics when incident beam was sufficiently intense. This has become a commonly used property, in that many of the lasers today (particularly emitting in the green, like YAG lasers) all use frequency doubling to produce visible output, as the diodes naturally output in the near IR.
To find out how it works, I recommend reading the paper, but I suspect you might not be convinced. Here’s why:
No doubled light as far as I can tell! Maybe they didn’t have peer review back in those days.
(I actually suspect it is the manner in which the digital copies were created. I’m going to check the library’s paper copy tomorrow.)