Miniature laser-pumped cesium cell atomic clock oscillator

Abstract

Our approach to a low-power compact atomic oscillator is based on the use of a diode laser to excite a small cell (/spl sim/0.1 cm/sup 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 /spl sigma/(/spl tau/)/spl tau//sup 1/2//spl les/2/spl times/10/sup -11/ for 10</spl tau/<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 /spl sigma/(/spl tau/)/spl tau//sup 1/2/=2.5/spl times/10/sup -10/, and /spl sigma/(/spl tau/)<3/spl times/10/sup -11/ for /spl tau/<1/spl times/10/sup 6/ s, without removal of drift. Current designs compatible with a power goal of 300 mW over a 0 to 50/spl deg/C temperature range, within a 25 cm/sup 3/ clock package are showing short term Allan deviation of /spl sigma/(/spl tau/)/spl tau//sup 1/2/<5/spl times/10/sup -11/.