We present the observation of optical fields carrying squeezed vacuum states
at sideband frequencies from 10Hz to above 35MHz. The field was generated with
type-I optical parametric oscillation below threshold at 1064nm. A coherent,
unbalanced classical modulation field at 40MHz 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 -4dB 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.Comment: 9 pages, 8 figure
