Optogalvanic spectroscopy of silicon atoms towards laser cooling of silicon

Summary form only given. Various atoms belonging to the elements of alkali metals, alkaline-earth metals, and rare gases have been cooled by laser since Haensch and Schawlow proposed laser cooling of atoms in 1975. The resonant frequencies for these atoms have been accessible with conventional lasers. By contrast, silicon atoms have not been the same case as these elements, while there are various potential applications such as atom lithography and atom holography. Therefore, we developed the light source for laser cooling of silicon atoms for the first time. The all-solid-state light source can radiate a continuous-wave and single-frequency coherent light at 252 nm whose linewidth is 11 MHz, which is narrow enough because the natural linewidth of the laser cooling transition is 29 MHz. Moreover, the deep ultraviolet output is stable, because the power fluctuation is less than 5%. Towards laser cooling of silicon atoms, we should know the accurate frequency of our light source. Therefore, we perform the optogalvanic spectroscopy of silicon atoms with a hollow-cathode lamp to set the frequency. In order to examine the performance of the silicon-hollow-cathode lamp, we demonstrated the spectroscopic experiment with the third harmonic coherent light of a ns Ti:sapphire laser, which provides 10 ns pulsed light with a 10 Hz repetition rate. Around 252 nm, we observed optogalvanic signals of neutral silicon atoms.