Dark-line atomic resonances in submillimeter structures

We present measurements of dark-line resonances excited in cesium atoms confined in submillimeter cells with a buffer gas. The width and contrast of the resonances were measured for cell lengths as low as 100 mm. The measured atomic Q factors are reduced in small cells because of frequent collisions of atoms with the cell walls. However, the contrast of coherent population trapping resonances measured in the small cells is similar in magnitude to that obtained in centimeter-sized cells, but substantially more laser intensity is needed to excite the resonance fully when increased buffer-gas pressure is used. The effect of the higher intensity on the linewidth is reduced because the intensity broadening rate decreases with buffer-gas pressure. OCIS codes: 020.1670, 300.6260. Compact frequency references have become increasingly important for military 1 and civilian 2 applications in recent years. For many applications in the f ield of navigation (e.g., global positioning systems) and communication systems, inexpensive miniature references with frequency stabilities in the 10 211 range at integration times approaching one day would be of great advantage. It has been predicted 3 that atomic clocks based on coherent population trapping (CPT) spectroscopy in millimeter-sized vapor cells might fulfill these requirements. It is well known that two phase-stable laser fields in resonance with a resonance line of the alkali atoms, and with a difference frequency equal to the hyperfine splitting, induce coherence between the two hyperfine ground