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Generation of Squeezed Vacuum Using Wavelength-Tunable Soliton Pulse and Nonlinear Polarization Interferometer

We demonstrate the generation of squeezed vacuum using a wavelength-tunable soliton pulse and nonlinear polarization interferometer (NOPI). Since the soliton pulse is ideal for squeezed vacuum generation and the wavelength of the soliton pulse can be tuned easily, it is expected that we can demonstrate large squeezing over a wide wavelength range. Using NOPI, since it is possible to generate squeezed light by only passing the optical pulse through the optical fiber without spatial alignment, the squeezed light can be generated easily and stably. A maximum noise reduction of -2.46 dB below shot noise level was observed. Considering the effect of quantum efficiency, the corresponding magnitude of squeezing is estimated to be -4.22 dB. The squeezing was observed when the center wavelengths were 1625 nm and 1650 nm.