Two-step pulse observation to improve resonance contrast for coherent population trapping atomic clock

Abstract

We study resonance contrast by a two-step pulse observation method to enhance the frequency stability of coherent population trapping (CPT) atomic clocks. The proposed method is a two-step Raman-Ramsey scheme with low intensity during resonance observation and high intensity after the observation. This method reduces the frequency variation in the light intensity and maintains a high signalto-noise ratio. The resonance characteristics were calculated by density matrix analysis of a Λ-type three-level system that was modeled on the 133 Cs D1 line, and the characteristics were also measured using a vertical-cavity surfaceemitting laser and a Cs vapor cell.

General analytical method of designing shielded coils for arbitrary axial magnetic field*

“…With the rapid development of quantum technology, specific magnetic field coils are increasingly required in many applications, [1] such as atomic clock, [2,3] optical pumped magnetometer, [4][5][6][7][8] nuclear magnetic resonance gyro, [9,10] and magnetic trap. [11][12][13][14][15] Although many kinds of magnetic coils [14][15][16][17][18][19][20][21][22][23] have been invented for these applications respectively, there is still a lack of a common method to design these coils conveniently, or even to realize any required magnetic field systematically.…”

“…Moreover, lots of these existing coils [18][19][20][21][22][23] neglect the influence of magnetic shield which is important for the application in weak magnetic field. [2,4,5] These deficiencies would inevitably impede the evolution of quantum technology.…”

Fast numerical analysis of the time response in coherent population trapping resonance based on Galerkin spectral method

“…An algorithm to calculate the time response of CPT resonance has been proposed for analyzing pulsed CPT resonance. 10,11) In this algorithm, the time is divided into short intervals, and the response is calculated for each section. By increasing the number of divisions, it can be applied to the analysis of CPT resonance under any perturbation.…”

“…To overcome this trade-off relation, we attempted to apply the Galerkin method using a Fourier series as a basis function (Galerkin spectral method) to the analysis of CPT resonance. 13) The Galerkin spectral method has been widely used in the numerical analysis of piezoelectric mechanical resonators such as quartz to reduce the calculation cost. 14,15) Unlike in previous works, a continuous function can be applied to calculate the time response in the new algorithm.…”

Light shift of the Ramsey resonance of coherent population trapping in optically dense medium

“…At present, a new direction of research is the search for ways to suppress the light shifts of CPT-resonance when using the Ramsey method by varying of the shapes of the pulses, their phases and amplitudesthe so-called generalized auto-balanced Ramsey spectroscopy [13]. The work [14] uses a two-stage pulse shape to simultaneously suppress light shifts and improve the signal-to-noise ratio. In [15] the density matrix formalism is constructed for atoms in an arbitrary periodic field.…”