Generation of vacuum ultraviolet radiation by intracavity high-harmonic   generation toward state detection of single trapped ions
  VUV radiation around 159 nm is obtained toward direct excitation of a single trapped $^{115}$In$^{+}$ ion. An efficient fluoride-based VUV output-coupler is employed for intracavity high-harmonic generation of a Ti:S oscillator. Using this coupler, where we measured its reflectance to be about 90%, an average power reaching $6.4\,\mu$W is coupled out from a modest fundamental power of 650 mW. When a single comb component out of $1.9\times10^{5}$ teeth is resonant to the atomic transition, hundreds of fluorescence photons per second will be detectable under a realistic condition. 
Kentaro Wakui, Kazuhiro Hayasaka, Tetsuya Ido
physics.atom-ph physics.optics