Coherent control of broadband vacuum squeezing

We present the observation of optical fields carrying squeezed vacuum states at sideband frequencies from 100.3em0exHz to above 350.3em0exMHz. The field was generated with type-I optical parametric oscillation below threshold at 10640.3em0exnm. A coherent, unbalanced classical modulation field at 400.3em0exMHz enabled the generation of error signals for stable phase control of the squeezed vacuum field with respect to a strong local oscillator. Broadband squeezing of approximately -40.3em0exdB was measured with balanced homodyne detection. The spectrum of the squeezed field allows a quantum noise reduction of ground-based gravitational wave detectors over their full detection band, regardless of whether homodyne readout or radio-frequency heterodyne readout is used.