The effect of mode matching on the preparation of the squeezed light at 1064 nm with periodically poled KTiOPO_4 (PPKTP) crystal is reported. We can derive the desired mode by improving the spatial mode matching into optical cavities, including the beam from the laser mode matched to the optical parametric amplifier cavity and mode cleaning cavity; also it is useful for the stability of the locking systems. By increasing the fringe visibility between the squeezed light and the local oscillator beam, a squeezing level of -8.75 dB or even higher could be observed, even with the same experimental parameters as described elsewhere.
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Chinese Academy of Sciences, Xi'an Institute of Optics and Precision Mechanics, State Key Laboratory of Transient Optics and Photonics, Xi'an 710119, China;
