Observation of Faraday Rotation in Cold Atoms in an Integrating Sphere

Abstract

The Faraday rotation of weak linearly polarized probe light is observed as it passes through a sample of cold 87 Rb atoms prepared by diffused light in an integrating sphere. The rotation angle of the probe light-polarization as functions of laser intensity, detuning and biased magnetic field is measured. A Ramsey fringe with a linewidth of 35 Hz and contrast up to 92% is demonstrated. This method has potential applications in improving the performance of atomic clocks with cold atoms.

Observation of magneto-optical rotation effects in cold $^{87}$Rb atoms in an integrating sphere

“…Lin et al have used faraday rotation method to detect clock signal in a vapor cell to improve its contrast to 90% [3]. We have observed faraday rotation signal in cold 87 Rb atoms in an integrating sphere and obtained a Ramsey fringe whose contrast is 92% [4]. The magneto-optical signal with cold atoms can also be interpreted by Larmor's theorem as a sensitive rotation of the atomic wavefunction reflecting the magnetic field, Optical Magnetometery techniques with Rubidium Bose-Einstein condensates (BEC) have recently been demonstrated with high spatial resolution [5,6].…”

“…In this work, we optimized and modified the previous experiment [4]. The main improvement is that: Firstly, an independent probe laser is used to eliminate additional noise, since both of the cooling and probe lights are from the same extended-cavity diode laser in Ref.…”

Non-resonant magneto-optical effects in cold atoms

“…These advantages render integrating sphere cooling an ideal cold atom source for a compact and small cold atom clock. We have observed the Faraday rotation signal in cold rubidium atoms in an integrating sphere which addressed the previously mentioned problem by removing the additional background noise [8] .…”

“…In this Letter, we present a different detection method with another probe light level, which brings out several desirable experimental results for rotational signals. In our previous scheme [8] , cold rubidium atoms were first obtained by a cooling laser (Toptica TA100) locked to the transition of 5 2 S 1∕2 ; F ¼ 2 → 5 2 P 3∕2 ; F 0 ¼ 3 and a repumping laser (Toptica DL100) locked to the transition of 5 2 S 1∕2 ; F ¼ 1 → 5 2 P 3∕2 ; F 0 ¼ 2. The probe laser (Toptica TA100) transition is from 5 2 S 1∕2 ; F ¼ 2 to 5 2 P 3∕2 ; F 0 ¼ 3.…”

“…We assume ideal analyzers in this content. The FS signals for weak-intensity light can be written as [8]…”