A pulsed-Laser Rb atomic frequency standard for GNSS applications

Abstract

We present the results of 10 years of research related to the development of a Rubidium vapor cell clock based on the principle of pulsed optical pumping (POP). Since in the pulsed approach, the clock operation phases take place at different times, this technique demonstrated to be very effective in curing several issues affecting traditional Rb clocks working in a continuous regime, like light shift, with a consequent improvement of the frequency stability performances. We describe two laboratory prototypes of POP clock, both developed at INRIM. The first one achieved the best results in terms of frequency stability: an Allan deviation of σy(τ) = 1.7 × 10−13 τ−1/2, being τ the averaging time, has been measured. In the prospect of a space application, we show preliminary results obtained with a second more recent prototype based on a loaded cavity-cell arrangement. This clock has a reduced size and exhibited an Allan deviation of σy(τ) = 6 × 10−13 τ−1/2, still a remarkable result for a vapor cell device. In parallel, an ongoing activity performed in collaboration with Leonardo S.p.A. and aimed at developing an engineered space prototype of the POP clock is finally mentioned. Possible issues related to space implementation are also briefly discussed. On the basis of the achieved results, the POP clock represents a promising technology for future GNSSs.

A Comprehensive Overview of Atomic Clocks and their Applications

“…It is worth noting the recent developments of ion-based compact high-performance clocks, and the developments of the rubidium pulsed clocks, and cold atom clocks for space-based navigation and scientific missions. 24,[42][43][44][45][46] The next section covers further details of the space based atomic clocks and overview of various navigation systems that contribute to Global Navigation Satellite Systems (GNSS).…”

“…These atomic clocks give a precise frequency and therefore timing output which helps to locate the precise position for navigating. 13,[42][43][44][45] Usefulness of atomic clocks is not only limited to earth, but beyond the earth's orbit for deep space tracking and navigation. 46,51,52 The lamp pumped Rb clocks are used in almost all Global Navigation Satellite Systems (GNSS).…”

Frequency characterization of diode lasers for vapor-cell clocks applications

“…In this paper, we will mainly address classes of lasers, such as distributed-Bragg-reflector (DBR) and distributed-feedback (DFB) lasers, that find application in vapor-cell frequency standards. The latter represent a promising technology for near future ground and space applications [11]- [13]. In these devices, laser frequency noise and RIN may significantly affect the clock signal.…”

Laser-written vapor cells for chip-scale atomic sensing and spectroscopy

“…In general, an atomic interaction size from 100 𝜇m to 1 mm, i.e. typically set by the transverse beam width, is desirable for Doppler-free applications [29], like atomic frequency references [61] and atomic clocks [62,63], as well as for high-sensitivity spin-based atomic sensors like optical magnetometers [64,65] and atomic gyroscopes [66]. The combination of the latter goal with integrated photonics led to state-of-the-art photonic-atomic chips, which make use of hybrid schemes where a separate mm or 𝜇m-sized microfabricated vapor cell is deposited on the top of the photonic chip [67,68].…”