Lineshape-asymmetry-caused shift in atomic interferometers

TL;DR

This paper identifies a new source of frequency shift in atomic interferometers caused by lineshape asymmetry due to laser chirping during pulses, with a unique inverse cubic dependence on pulse interval duration, affecting compact device accuracy.

Contribution

It introduces the concept of lineshape-asymmetry-caused shift (LACS) and derives its inverse cubic dependence on the Ramsey pulse interval, highlighting its significance in compact atomic interferometers.

Findings

LACS depends on the chirping rate during pulses.

The shift scales as 1/T^3, contrasting with the typical 1/T^2.

For short intervals, the shift can reach 0.1-1 Gal.

Abstract

We investigate the shift caused by asymmetry of spectroscopic lineshape in atomic interferometers, which has not previously been discussed in the scientific literature. This asymmetry arises because laser field is frequency-chirped not only during the free-evolution intervals of atoms, but also during the Ramsey pulses. As a result, the effective detuning from the working atomic transition during the pulses also depends on the chirping rate, which, in turn, leads to the lineshape-asymmetry-caused shift (LACS). It is shown that this shift has an inverse cubic dependence of $\propto 1/T^3$ on the duration of the interval between the Ramsey pulses $T$, which markedly contrasts with the $\propto 1/T^2$ dependence typical in atomic interferometry. Therefore, the metrological importance of this shift substantially increases for compact atomic interferometers with a short baseline. For example, for interferometers-gravimeters using two-photon transitions in rubidium atoms, at $T\sim 1$~ms we estimate the LACS shift and its variations at the level of 0.1-1~mGal, while for $T\sim 100$~$\mu$s this can reach a value of 0.1-1~Gal.