Double-resonance in alkali vapor cells for high performance and miniature atomic clocks

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) <; 1.4×10^-13 τ^-1/2 and a miniaturized clock with σ_y(τ) <; 1×10^-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.