The Chip-Scale Atomic Clock - Recent developments

Abstract

We report on recent advances in the core performance and capabilities of the Chip-Scale Atomic Clock.

Temperature Dependence Cancellation of the Cs Clock Frequency in the Presence of Ne Buffer Gas

“…HE coherent population trapping (CPT) phenomenon [1] has been investigated by several laboratories for a few years in view of applications to atomic clocks [2,3,4]. The CPT has renewed the interest in the use of the cesium atom in atomic vapour cell clocks, when they were until now based on rubidium.…”

Metrological characterization of custom-designed 8946 nm VCSELs for miniature atomic clocks

“…These compact, low-power, low-threshold current and high-modulationbandwidth lasers-despite their broad linewidth (100 MHz typically)-have demonstrated their potential to detect narrow-linewidth CPT resonances in alkali vapor cells [3]. Later, it was shown that excitation on the D 1 line results in higher contrast and narrower CPT resonances than excitation on the D 2 line, for Rb [4] as well as for Cs [5]. While VCSELs on the Rb D 1 line can be found easily, VCSELs emitting on the Cs D 1 line at 894.6 nm are not commercially available yet.…”

“…The RIN is measured to be 1 × 10 −11 Hz −1 at 10 Hz and 5 × 10 −15 Hz −1 at 10 kHz Fourier frequencies. The frequency noise of the VCSEL is known to be one of the main limitations to the short-term frequency stability of miniature atomic clocks [14], due to frequency-to-amplitude noise conversion in the atomic vapor that degrades the clock's signal-to-noise ratio [5,15]. As a second effect, the laser frequency noise also limits the frequency stability achievable for the frequency-stabilized laser, which at longer integration times can result in significant clock instability contributions via the frequency light-shift effect [16], as detailed in the following.…”

Utilising diffractive optics towards a compact, cold atom clock

“…This stability is most notable in the atomic fountain and lattice clocks, measuring frequencies at the 10 −16 τ −1/2 and 10 −18 τ −1/2 level respectively [6], [7], [8], [9]. This research has also lead to profound advancement of compact metrological devices, achieving frequency stabilities in the low 10 −10 τ −1/2 in package volumes measuring only a few tens of cubic centimetres [10], [11]. However, the majority of the current compact clocks are based around room temperature apparatus that use buffer gasses and cell wall coatings in order to minimise collisional spin flips, benefiting the system with increased contrast and interrogation times [12].…”