Generation of a squeezed vacuum resonant on Rubidium D_1 line with   periodically-poled KTiOPO_4
  We report generation of a continuous-wave squeezed vacuum resonant on the Rb D_1 line (795 nm) using periodically poled KTiOPO_4 (PPKTP) crystals. With a frequency doubler and an optical parametric oscillator based on PPKTP crystals, we observed a squeezing level of -2.75 +- 0.14 dB and an anti-squeezing level of +7.00 +- 0.13 dB. This system could be utilized for demonstrating storage and retrieval of the squeezed vacuum, which is important for the ultra-precise measurement of atomic spins as well as quantum information processing. 
Takahito Tanimura, Daisuke Akamatsu, Yoshihiko Yokoi, Akira Furusawa,   and Mikio Kozuma