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General description of used
Wavelength Meter
's for sale.
A wavelength meter is a kind of interferometer which is used for precise wavelength measurements on laser beams. There are different variants, including scanning wavemeters and static devices with no moving parts.
The most common type is based on a Michelson interferometer. Light from the optical source under test is sent into the Michelson interferometer, while the length of one of interferometer arms is scanned through a certain range. The period of the output power recorded by the photodetector with respect to the arm length changes then reflects the wavelength. Depending on the quality of the device, the achieved wavelength accuracy can be 0.01 nm.
A Fizeau interferometer uses two plane reflecting surfaces with a slight deviation from exact parallelity. Effectively, two copies of the input beam are superimposed with a slight relative angle, leading to an interference pattern, the period of which depends on the wavelength.
The accuracy of the wavelength meter varies between some fraction of a nanometer to far below 1 pm, and can depend on the wavelength. One should not confuse accuracy with resolution: a high accuracy requires not only a high resolution of the display, but also a high stability of the setup including the reference laser. The measurement speed of a wavelength meter can be higher with static devices. Wavemeters work only in a limited wavelength range. Some wavemeters can display not only the wavelength but also the linewidth.
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