Brieussel, Alexandre
Description
Squeezed states of light are quantum states that can be used in
numerous protocols
for quantum computation and quantum communication. Their
generation in labora-
tories has been investigated before, but they still lack
compactness and practicality
to easily integrate them into larger experiments.
This thesis considers two experiments: one conducted in France,
the miniOPO; and
one conducted in Australia, the SquOPO. Both are new designs of
...[Show more] compact sources
of squeezed states of light towards an integrated system.
The miniOPO is a linear cavity of 5mm length between the end of a
fiber and a
curved mirror with a PPKTP crystal of 1mm inside it. The
squeezing generated
in this cavity is coupled into the fiber to be able to be brought
to a measurement
device (homodyne) or to a larger experiment. The cavity is
resonant for the squeezed
light and the pump light, and locked in frequency using
self-locking effects due to
absorption of the pump in the crystal. The double resonance is
achieved by changing
the temperature of the crystal.
Two different fibers have been tested in this experiment, a
standard single-mode
fiber and a photonic large core single-mode fiber.
The squeezing obtained is still quite low (0.5dB with the
standard fiber and 0.9dB
for the photonic fiber) but a number of ameliorations are
investigated to increase
these levels in the future.
The SqOPO is a monolithic square cavity made in a Lithium Niobate
crystal using
four total internal reflections on the four faces of the square
to define an optical mode
for the squeezed mode and the pump mode. The light is coupled in
the resonator
using frustrated internal reflection with prisms. The distance
between the prisms
and the resonator defined the coupling of the light, which allows
us to control the
finesse of the light in the resonator and by using birefringent
prisms it is possible
to tune independently the two frequencies in the resonator to
achieve an optimal
regime. The frequency of the light is locked using absorption of
the pump light in
the resonator to achieve self-locking, and double resonance is
controlled by tuning
the temperature of the crystal.
We demonstrated 2.6dB of vacuum squeezing with this system. Once
again, the
amount of squeezing is low, but ameliorations that could be
implemented in the
future are discussed.
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