Microwave Frequency Characterisation of Squeezed Light From an Optical Parametric Oscillator
Date
2006
Authors
Senior, Roger J
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Abstract
The quantum statistics of a laser result in noise when measurements of the beam are
made. This noise sets a classical limit beyond which a laser cannot be used with increasing
sensitivity. This quantum noise limit is imposed on many of the uses of lasers currently,
especially in power limited devices such as optical communications. The statistics of the
laser photon field can be modified to produce a non-classical state resulting in lower noise
than the quantum noise limit when detected appropriately. This state, called a squeezed
state, has been measured previously from a cavity enhanced optical parametric oscillator
(OPO) only at frequency sidebands within the linewidth of the cavity.
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This thesis reports measurements of squeezing at microwave frequency sidebands on
an optical beam produced by an optical parametric oscillator. This is the first reported
measurement of squeezing at frequency sidebands at higher longitudinal modes of the
cavity from an OPO. Noise reduction below the quantum noise limit is measured at sideband
frequencies of 5 MHz, 1.7 GHz, 3.4 GHz and 5.1 GHz, corresponding to the zeroth,
first, second and third longitudinal modes from the squeezed beam. These results are the
highest frequency sideband measurements of squeezing to date. In addition to measuring
squeezing at different longitudinal modes for the fundamental Gaussian spatial mode,
non-classical noise reduction is measured at the same frequencies for a squeezed higher
order spatial mode, TEM10.
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A single mode theoretical model of the OPO is presented, based on the work of ref.
[1]. Computer simulations of the squeezing predicted by this model are developed and
compared to the experimental results, showing excellent agreement between the different
longitudinal modes for each of the two spatial modes measured.
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Physics, Quantum optics
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Thesis (Honours)
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