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Definition: devices for precise measurements of laser wavelengths
A wavemeter (or wavelength meter) is a kind of interferometer which is used for precise wavelength measurements on laser beams. The output power of the interferometer is monitored while the arm length difference is linearly scanned. The period of the output power with respect to the arm length changes then reflects the wavelength. Typically, the wavemeter output is calibrated by simultaneously recording the signal from a reference laser with known wavelength.
The principle of a wavemeter can be extended for the measurement of the optical spectrum of non-monochromatic sources. Essentially, the spectrum is obtained by applying a Fourier transform to the detected power versus arm length difference. This method is called Fourier transform spectroscopy.
The precision of wavemeters is limited by various factors, including counting errors, wavefront distortions, and the uncertainty in the frequency of the reference laser. Higher precision can be achieved with optical frequency measurements (→ frequency metrology), which are immune to wavefront distortions.
Bibliography
| [1] | R. Castell et al., “The accuracy of laser wavelength meters”, Appl. Phys. B 38 (1), 1 (1985) |
| [2] | D. F. Gray et al., “Simple compact Fizeau wavemeter”, Appl. Opt. 25 (8), 1339 (1986) |
| [3] | P. J. Fox et al., “A reliable, compact, and low-cost Michelson wavemeter for laser wavelength measurement”, Am. J. Phys. 67 (7), 624 (1999) |
| [4] | J. J. Snyder and T. W. Hänsch, “Laser Wavemeters”, in Topics in Applied Physics: Dye Lasers (ed. F. P. Schäfer), Springer, Berlin (1973) |
See also: interferometers, frequency metrology
Categories: metrology, photonic devices
