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Japanese Journal of Applied Physics

Observation of Ramsey-Type Resonant Fringe Using a Cylindrical Microwave Cavity for a Diode Laser-Pumped Rb Beam Atomic Clock

Hiroyuki Furuta, Hiromasa Suzuki, Motoichi Ohtsu

Published Mar 1, 1991• 3 citations
Publisher

Abstract

A novel Ramsey-type resonance signal is observed by using a simple microwave cylindrical cavity in a diode laser-pumped rubidium atomic clock. Its linewidth is 1.1 kHz. The signal lineshapes depend on the modal profile of the microwave magnetic field inside the cavity. The lineshapes are reproduced by numerical calculation. Conditions to achieve the maximum frequency discrimination sensitivity are derived by the theoretical analysis.

DOI
10.1143/jjap.30.596

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Precise measurement of the shift (i.e. microwave frequency shift induced by the electric field of the pumping light) in a rubidium atomic clock pumped by a semiconductor laser is discussed. The spectral lineshape of the microwave resonance, which is used as a frequency discriminator for the atomic clock in the optical microwave double resonance experiment, depends strongly on the spatial distribution of the laser beam intensity, laser frequency detuning, and modulation parameters of the microwave frequency. Based on measurements of the deformation of the resonance lineshape, a self-tuning system was built to compensate for the effect of light shift. As a result of controlling the laser frequency with this system, long-term drift of the microwave frequency as low as 6.3*10/sup -13//h was obtained.>
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We report a high-performance pulsed optically pumped (POP) Rb clock based on a novel magnetron-type microwave cavity. The cavity has a volume of 30 mL, enabling a highly homogenous microwave field distribution. With the laser frequency tuning to the ground-state hyperfine level F = 2 of the D2line, we observe a Ramsey fringe contrast of 52% in terms of optical absorption detection. The resultant shot noise limit is estimated to be 1.6 × 10-14τ-1/2. The clock frequency stability is measured as 2.3 × 10-13τ-1/2(1-100 s), which is limited by the relative intensity noise of the light.