142 research outputs found
Generation of Polarization Squeezing with Periodically Poled KTP at 1064 nm
We report the experimental demonstration of directly produced polarization
squeezing at 1064 nm from a type I optical parametric amplifier (OPA) based on
a periodically poled KTP crystal (PPKTP). The orthogonal polarization modes of
the polarization squeezed state are both defined by the OPA cavity mode, and
the birefringence induced by the PPKTP crystal is compensated for by a second,
but inactive, PPKTP crystal. Stokes parameter squeezing of 3.6 dB and anti
squeezing of 9.4 dB is observed.Comment: 4 pages, 2 figure
A 1D "Navier-Stokes Machine" and its application to turbulence studies
In the present work, we investigate a numerical one-dimensional solver to the
Navier-Stokes equation that retains all terms, including both pressure and
dissipation. Solutions to simple examples that illustrate the actions of the
nonlinear term are presented and discussed. The calculations take the full 4D
flow as its starting point and continuously projects the forces acting on the
fluid at a fixed Eulerian point onto the direction of the instantaneous
velocity. Pressure is included through modeling. Adhering to the requirement
that time must in general be considered an independent variable, the time
development of the time records and power spectra of the velocity fluctuations
are studied. It is found that the actions of the nonlinear term in the
Navier-Stokes equation manifests itself by generating sharp pulses in the time
traces, where the sharpness is bounded by the finite viscosity. In the spectral
domain, the sharp gradients in the pulses generate energy contributions at high
frequencies that yields a slope across the inertial range. The (or
) slope is explained through a simple example and the classically
expected slope in the inertial range can be recovered from the pressure
fluctuations from the full flow field that can be considered a noise
contribution at the point considered. We also observe that the spectrum can in
principle keep spreading to higher frequencies or wavenumbers without upper
bound, as the viscosity is approaching the zero limit
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