Observation of-9 dB quadrature squeezing with improvement of phase stability in homodyne measurement

We observe -9.01 +/- 0.14 dB of squeezing and +15.12 +/- 0.14 dB of antisqueezing with a local oscillator phase locked in homodyne measurement. Suzuki et al. have pointed out two main factors in [Appl. Phys. Lett. 89, 061116 (2006)], which degrade the observed squeezing level: phase fluctuation in homodyne measurement and intracavity losses of an optical parametric oscillator for squeezing. We have improved the phase stability of homodyne measurement and have reduced the intracavity losses. We measure pump power dependences of the squeezing and antisqueezing levels, which show good agreement with theoretical calculations taking account of the phase fluctuation. (c) 2007 Optical Society of America.