Move over, quartz: the atomic clock gets smaller and cheaper

While the standard quartz watch maybe less expensive, engineers still prefer to use atomic clocks because of the many advantages they offer. A good example is the new atomic clock that operates using a radio signal linked to the atomic standard. Its core is the size of a grain of rice, i.e. chip-scale, because it is made with standard microelectronic manufacturing techniques. The chip-scale clock uses some of the same principles as the standards institute's primary clock, which is about the size of a compact automobile. In both, electromagnetic radiation causes cesium atoms in a vapor, which is enclosed in a cell, to oscillate at a stable frequency. In the primary clock, the radiation is a microwave field, while in the chip-scale clock it is pulses of infrared light from a laser, and everything but the vapor is solid state. The chip-scale clock is a work in progress but researchers have built a physics package, which contains the enclosure for the cesium atoms, the laser, the optics and the photodiodes.