摘要：

It has been discovered that crystalline calcite may be used as an excellent dichroic polarizer in certain regions of the infrared between 2.5 μ and 16 μ where previously only rather unsatisfactory polarizers were available. The performance of the new polarizers is particularly good for radiation from the high-gain laser lines of helium–neon at 3.39 μ and helium–xenon at 3.507 μ, and their use has greatly assisted in the investigation of these lines. Some typical applications are the measurement of Zeeman effects, measurement of noise properties, use in modulators, circulators, and optical attenuators. The polarizer takes the form of a thin plate of calcite correctly cut from the crystal. For a 1-mm thick piece measured at 3.507 μ, the minor principal attenuation is 1 dB. (To obtain the optical density, we divide the dB value by 10.) The major principal attenuation is 120 dB, but, in practice, it is limited by scattering to around 80 dB. The acceptance angle is about 30°.

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