Frequency Conversion Crystals
An Optics Processing technician inspects a frequency conversion crystal in the off-line laser conditioning facility. Frequency conversion crystals convert the infrared light produced by NIF’s neodymium glass lasers at a fundamental wavelength of 1,053 nanometers (one omega, or 1ω) to 351-nm ultraviolet light (3ω) (inertial confinement fusion targets perform more efficiently when driven with ultraviolet light). The process occurs in two steps. The 1ω light first passes through a doubling crystal made of potassium dihydrogen phosphate (KDP), which converts two-thirds of the 1,053-nm radiation to the 527-nm second harmonic (2ω) wavelength (visible green light). A second “tripling” crystal then mixes that radiation with the remaining infrared light to produce 351-nm ultraviolet radiation at the third harmonic (3ω).
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