Accurate laser wavelength measurement with a precision two-beam scanning Michelson interferometer

Abstract

This paper gives the details of a precision two-beam scanning Michelson interferometer, designed and perfected for accurate comparison of an unknown laser wavelength and the precisely calibrated wavelength of a reference laser. An iodine Lamb-dip stabilized He-Ne 633-nm laser (calibrated with respect to a Kr standard) is used as the reference. The design incorporates features to minimize instrumental errors and the effect of fringe shifts caused by diffraction (in the IR). It is applied to accurate measurements of a stable CO(2) laser wavelength tuned to the centers of its various transitions. Measurements are done by simultaneous fringe counting and relative fringe-phase comparison at the two wavelengths using on-line data storage and processing with an electronic digital computer. The accuracy in the 10-microm region is several parts in 10(9) and is limited by correction for diffraction fringe shifts. Because of its low-Q and broadband operating characteristics, it can be applied to rapid accurate laser wavelength measurements over the entire wavelength range permitted by its transmitting optics. In the visible range where the diffraction correction is small, the interferometer can be used to perform measurements to within several parts in 10(11). The paper gives theoretical derivation of various diffraction corrections, the design and construction of the interferometer, the alignment procedures, detailed analysis of various error sources, and data processing. It also gives the details of a previously reported accurate measurement of the speed of light using the measured wavelength of the CO(2) R(14) line and its known frequency.

Calibration of a Michelson-type laser wavemeter and evaluation of its accuracy

“…The WA-1500 wavemeter uses a Michelson interferometer to generate sinusoidal interference fringes from the input radiation [6][7][8][9][10][11][12]. The optical layout is shown schematically in Fig.…”

Xenon and hydrogen gas mixtures as laser active media

“…This beam can be described by an intensity distribution with an angular distribution of wavevectors across its finite aperture. For this case the change of the wavenumber is discussed in the literature [13,14] with the estimation for the centre of the beam…”

Wavemeter uncertainty evaluation for the calibration of external cavity diode lasers

“…A mathematical model for the wavelength uncertainty of the wavemeter was proposed taking into account all contributions [10][11][12][13][14][15][16][17]: Wavelength correction due to wavefront curvature of the unknown laser λ WCR Wavelength correction due to wavefront curvature of the reference laser λ ALIGU Wavelength correction due to unknown laser beam misalignment λ ALIGR Wavelength correction due to reference laser beam misalignment λ TEMP Wavelength correction due to thermal expansion λ CIDOR Wavelength correction due to air refractive index, (made with Cidor equation) λ VIB Wavelength correction due to optical system vibration In equation (2) the first term can be simplified to λ U = λ R (N R /N U ) due to the difference between the refractive index of air of both laser beams is less than 0.01ppm, in our laboratory environmental conditions through Cidor equation [18]. This occur because of the similarity between the wavelength of reference and unknown lasers (<0,005 nm).…”