Frequency of the methane-stabilized He–Ne laser at 88 THz measured to ±3 parts in 10¹¹

Abstract

We have measured the frequency of methane-stabilized laser at 88 THz (3.39 µm) (ref. 1), by method which largely eliminates the uncertainties contributed by lower-frequency lasers used as transfer oscillators. This result is primarily of interest for proposed new definition of the metre in which the speed of light in vacuum (c₀) would be kept constant and reference would be m de to the standard of time and frequency². For this re son our measurement has been referred to the me an frequency of five small portable, stabilized lasers of similar design that re used as wavelength standards^3,4. We estimate the me an frequency of the laser ensemble to have been (88, 376, 181, 616 ±3) kHz. The estimated standard deviation comes within about factor of 2 of the reproducibility of the lasers themselves. This result therefore demonstrates degree of accuracy that would permit the choice of definition of the metre in which c₀ was kept constant, without substantial loss of accuracy compared with choosing definition based on the wavelength of selected stabilized laser.