On the performance of wavelength meters: Part 2—frequency-comb based characterization for more accurate absolute wavelength determinations

Abstract

Wavelength meters are widely used for frequency determinations and stabilization purposes since they cover a large wavelength range, provide a high read-out rate and have specified accuracies of up to 10 −8 . More accurate optical frequency measurements can be achieved with frequency combs but only at the price of considerably higher costs and complexity. In the context of precise and accurate frequency determinations for high-resolution laser spectroscopy, the performance of five different wavelength meters was quantified with respect to a frequency comb. The relative precision as well as the absolute accuracy has been investigated in detail, allowing us to give a sophisticated uncertainty margin for the individual instruments. We encountered a prominent substructure on the deviation between both device types with an amplitude of a few MHz that is repeating on the GHz scale. This finally limits the precision of laser scans which are monitored and controlled with wavelength meters. While quantifying its uncertainty margins, we found a high temporal stability in the characteristics of the wavelength meters which enables the preparation of wavelength-dependent adjustment curves for wide-and short-ranged scans. With this method, the absolute accuracy of wavelength meters can be raised up to the MHz level independently from the wavelength of the reference laser used for calibrating the device. Since this technique can be universally applied, it can lead to benefits in all fields of wavelength meter applications.

On the performance of wavelength meters: Part 1—consequences for medium-to-high-resolution laser spectroscopy

“…4, it follows that similar periodic patterns arise at different wavelength ranges, with similar peak-to-peak discrepancies for both wavelength meters. The structure is found to be highly reproducible over months in previous measurements performed at COALA [1]. Inspecting both Figs.…”

“…Nowadays, precise measurements of absolute transition frequencies and isotope shifts in ions are also performed to benchmark atomic theory and to support on-line investigations of shortlived isotopes. For this purpose, a cw laser system based on Ti:sapphire lasers combined with Wavetrain frequency doublers is available alongside a GPS-referenced frequency comb to determine and stabilize its frequency [1,26,27].…”

“…In this paper, we report on a reliability study performed in different laboratories using different wavelength ranges, different wavelength meters and different measuring protocols with the goal to provide an easy, cost-friendly, widely-applicable and potentially performance-increasing, wavelength meter characterization procedure. The wavelength meters of interest in this paper and [1] belong to the WS series from HighFinesse GmbH. These devices consist of beam optics coupling the laser light, entering the device via an optical fiber, into Fizeau interferometers.…”

“…Here, we will concentrate on the accuracy of relative frequency measurements, while in a second study, the focus will lie on the accuracy of absolute frequency determinations [1]. To determine the precision on ν αβ , ∆ν αβ , for different wavelength meters in different wavelength ranges, the readout of these devices was compared to another reference.…”

“…In this paper, a practical and relatively inexpensive wavelength meter characterization procedure is presented and validated. This method is capable of improving the precision on wavelength differences considerably depending on the device, while together with a second investigation that is published separately, [1], it offers a full description of the expected wavelength meter performance for users.…”