Abstract

We have clearly demonstrated the parametric deamplification of electromagnetic vacuum fluctuations in a traveling wave geometry using a single-mode optical fiber.¹ The minimum detected noise level was 12.5 ± 0.5% below the noise level produced by an incandescent source at the same photocurrent. Noise levels below the standard quantum limit appeared in two 9-MHz wide frequency bands centered at 45 and 56 MHz. At other frequencies, noise due to guided acoustic wave Brillouin scattering overwhelmed the squeezing, even at 2 K. Stimulated Brillouin oscil­lation was avoided by dividing the pump wave into many frequency components with a phase modulator. The theory of squeezed state generation and detection with such a multifrequency pump is discussed as are the phenomena which limit the noise suppression by this technique.

© 1986 Optical Society of America