In physics, a FASOR is an acronym for Frequency Addition Source of Optical Radiation. It is a device similar to a laser where the emitted light is produced in a sum-frequency generation process from two laser sources that operate at a different wavelength. The frequencies of the sources add directly to a summed frequency. Thus, if the source wavelengths are λ1 and λ2, the resulting wavelength is
Applications
The FASOR in the image is used for laser guide star experiments. It is tuned to D2A hyperfine component of the sodium D line and used to excite sodium atoms in the mesospheric upper atmosphere. It consists of single frequency injection locked Nd:YAG lasers close to 1064 and 1319 nm that are both resonant in a cavity containing a Lithium Triborate (LBO) crystal which sums the frequencies yielding 589.158 nm light.
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