We present our studies on a compact high-performance continuous wave (CW) double-resonance (DR) rubidium frequency standard in view of future portable applications. Our clock exhibits a short-term stability of 1.4 × 10(-13) τ(-1/2), consistent with the short-term noise budget for an optimized DR signal. The metrological studies on the medium- to longterm stability of our Rb standard with measured stabilities are presented. The dependence of microwave power shift on light intensity, and the possibility to suppress the microwave power shift is demonstrated. The instabilities arising from the vapor cell geometric effect are evaluated, and are found to act on two different time scales (fast and slow stem effects). The resulting medium- to long-term stability limit is around 5.5 × 10(-14). Further required improvements, particularly focusing on medium- to long-term clock performance, are discussed.

Analysis of the mode composition of an X-band overmoded O-type Cerenkov high-power microwave oscillator Phys. Plasmas 19, 103102 (2012) Gap independent coupling into parallel plate terahertz waveguides using cylindrical horn antennas J. Appl. Phys. 112, 073102 (2012) A band-pass filter approach within molecular dynamics for the prediction of intrinsic quality factors of nanoresonators J. Appl. Phys. 112, 074301 (2012) A research of W-band folded waveguide traveling wave tube with elliptical sheet electron beam Phys. Plasmas 19, 093117 (2012) Additional information on Rev. Sci. Instrum. The design, realization, and characterization of a compact magnetron-type microwave cavity operating with a TE 011 -like mode are presented. The resonator works at the rubidium hyperfine ground-state frequency (i.e., 6.835 GHz) by accommodating a glass cell of 25 mm diameter containing rubidium vapor. Its design analysis demonstrates the limitation of the loop-gap resonator lumped model when targeting such a large cell, thus numerical optimization was done to obtain the required performances. Microwave characterization of the realized prototype confirmed the expected working behavior. Double-resonance and Zeeman spectroscopy performed with this cavity indicated an excellent microwave magnetic field homogeneity: the performance validation of the cavity was done by achieving an excellent short-term clock stability as low as 2.4 × 10 −13 τ −1/2 . The achieved experimental results and the compact design make this resonator suitable for applications in portable atomic high-performance frequency standards for both terrestrial and space applications.

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-We present two lines of investigations on vapor cell based laser-microwave double-resonance (DR) rubidium atomic frequency standards: a compact high-performance clock exhibiting σ y (τ) < 1.4x10 -13 τ -1/2 and a miniaturized clock with σ y (τ) < 1x10-11 τ -1/2. The applications of these standards are emphasized towards portable applications such as next generation GNSS, deep space missions and telecommunications. Other techniques for DR clocks are discussed in brief.

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