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 (similar to 0.1 cm(3)) 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 sigma(tau)tau(1/2) less than or equal to 2 x 10(-11) for 10 < tau < 200s. 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 sigma(tau)tau(1/2) = 2.5 x 10(-10), and sigma(tau) < 3 x 10(-11) for tau < 1 x 10(6) s, without removal of drift. Current designs compatible with a power goal of 300 mW over a 0 to 50 degrees C temperature range, within a 25 cm(3) clock package are showing short term Allan deviation of sigma(tau)tau(1/2) < 5 x 10(-11).