Lamb-dip stabilized 543-nm He-Ne lasers and isotope shift of Ne 3s2→ 2p10 transition

Internal-mirror 543-nm He-20Ne and He-22Ne lasers are frequency-stabilized to the Lamb-dip of their tuning curves. Frequency stability of 2×10−11 and frequency resettability of 4×10−9 (or 2 MHz) are achieved. The absolute frequencies of the two lasers are determined by frequencycomparing with an iodine-stabilized 543-nm laser. The isotope shift between 20Ne and 22Ne is measured to one order of magnitude more accurately than the previous result, and the specific-mass-shift for Ne 3s2→ 2p10 transition is also determined. PACS: 35; 42.55.H; 42.80 Early in 1963, the power saturation dip of a single-mode gas laser, which is referred to as “Lamb-dip” now, was theoretically predicted [1, 2] and experimentally realized [3]. In 1965, Shimoda and Javan first successfully frequency-stabilized a 1.15-μm He-Ne laser to the center of the Lamb-dip and they also gave a detail analysis on such a system [4]. Later, Hall pointed out that the Lamb-dip stabilized lasers are not suitable for primary wavelength standards due to the pressure shift and asymmetric line shape in the Lamb-dip [5]. However, the Lamb-dip stabilized lasers can serve as the secondary wavelength standards for some metrology applications since they have sufficient long-term and short-term stability (10−8 resettability and 10−11 stability typically [5, 6]). Besides, Lamb-dip stabilized He-Ne lasers are handy and convenient compared with the corresponding primary wavelength standard lasers. For example, some applications used the Lamb-dip stabilized lasers together with a high-finesse Fabry–Pérot etalon as the absolute frequency references [7– 11]. Therefore, detailed studies and the absolute frequency measurements of the Lamb-dip stabilized lasers are significant for generalizing their applications. The first iodine-stabilized 543-nm He-Ne laser system was reported in 1989 [12], and many efforts on such a wavelength standard laser system have been performed since then [13–18]. The iodine-stabilized 543-nm He-Ne laser was adopted as a recommended wavelength standard in 1992 [19]. However, the complicated configurations of those systems limited its applications and only one inter-comparison for the iodine-stabilized 543-nm lasers was performed up to now. Recently we reported a compact and highly stable iodinestabilized 543-nm He-Ne laser system [19] which is easy to maintain. Hence it is worthwhile to investigate the corresponding secondary wavelength standard laser systems, such as the Lamb-dip stabilized lasers for extending the use of such a wavelength standard. On the other hand, as the Lamb-dip stabilized He-20Ne, He-22Ne lasers have the frequencies very close to their atomic transition centers, beat frequency measurements between the Lamb-dip stabilized He-20Ne, He-22Ne lasers thus provide a good way to determine the isotope shift between 20Ne and 22Ne atoms precisely. The determined isotope shift is important in searching the specific-mass-shift (SMS) of Ne atom which is of interest to the nuclear and atomic physicists in the understanding of the nuclear structure and the J-dependence of the electronic wavefunction of the excited state of Ne atom. In the past, the isotope shifts of the Ne atom at the 3391-nm [20], 1523-nm [6], 1152-nm [21], and 633-nm [22] laser transitions have been determined by the Lamb-dips of the corresponding He-Ne lasers. In this paper, we report on our results of the Lamb-dip stabilization of internal-mirror 543-nm He-Ne lasers. We have constructed two Lamb-dip stabilized 543-nm He-Ne lasers with a frequency stability of 2×10−11 (normalized to 1 Hz bandwidth) and a frequency resettability of 4×10−9. We have also determined the frequencies of the two Lamb-dip stabilized lasers of different isotopes (20Ne and 22Ne) with respect to an iodine-stabilized laser. From this, we can deduce the isotope shift (1014±5 MHz) between 20Ne and 22Ne in 3s2→ 2p10 (Paschen notation) transition and also its specificmass-shift (SMS) (253±5 MHz). Our result of isotope shift is one order of magnitude better than Gerstenberger, Drobshoff, and Sheng’s work [23] in accuracy. The previous results for the isotope shift of Ne 3s2→ 2p4 633-nm laser transition [22, 24] yield an averaged SMS of−291±9 MHz. The