Miniature laser-pumped cesium cell atomic clock oscillator

Our approach to a low-power compact atomic oscillator is based on the use of a diode laser to excite a small cell (~0.1 cm³) containing cesium vapor and buffer gases. Laser wavelength and power are controlled solely with current and temperature, providing a compact, low-power, rugged, spectrally-pure, collimated optical source. A succession of physics packages, when operated with analog laboratory electronics, have typically given short term Allan deviation of σ(τ)τ^1/2⩽2×10^-11 for 10<τ<200 s. The clock electronics uses a single microprocessor, with time division multiplexing of the numerous control loops. A physics package operated uninterrupted for 285 days with first generation digital electronics, gave short term σ(τ)τ^1/2=2.5×10^-10, and σ(τ)<3×10^-11 for τ<1×10⁶ s, without removal of drift. Current designs compatible with a power goal of 300 mW over a 0 to 50°C temperature range, within a 25 cm³ clock package are showing short term Allan deviation of σ(τ)τ^1/2<5×10^-11