Mansell, Georgia L
The era of gravitational-wave astronomy has begun, with the
detection of 5 confirmed binary black holes and a binary neutron
star coalescence by the Advanced Laser Interferometer
Gravitational- wave Observatory (aLIGO), and later with the
advanced Virgo detector. These detections have already revealed a
wealth of discoveries across the fields of nuclear physics,
general relativity and astrophysics. The work presented in this
thesis is part of the ongoing...[Show more] effort to improve the sensitivity
of ground-based interferometric gravitational-wave detectors.
The sensitivity of aLIGO, and other interferometric detectors, is
broadly limited by quantum noise. Improving on the quantum noise
will increase the astrophysical range of the detectors, and
improve the source parameter estimation. One way to reduce
quantum noise is to inject audio- band squeezed vacuum states
into the detection port. This technique has been demonstrated on
the initial LIGO and GEO600 detectors. A squeezed light source
for aLIGO must meet stringent requirements in terms of optical
loss, phase noise, and scattered light. The squeezer must produce
high levels of audio-band squeezing and operate under vacuum, to
take advantage of the excellent existing isolation systems and to
minimise optical loss. At design sensitivity, squeezed states
whose quantum noise depends on frequency will be required.
We have demonstrated an ultra-stable glass-based squeezed light
source, the first experiment of this kind to operate under
vacuum. The squeezer cavity is constructed quasi-monolithically,
with optics and nonlinear crystal oven optically contacted to a
breadboard base. The cavity is designed to have extremely low
length noise, and to produce high levels of audio-band squeezing.
We have measured 8.6 ± 0.9 dB of squeezing and infer the
generation of 14.2 ± 1.0 dB after accounting for all known
losses. The squeezer has demonstrated record phase noise
performance of 1.3 mradRMS, dominated by sources other than
cavity length noise. This exceeds the phase-noise requirement for
a squeezer for aLIGO. A copy of this squeezer is currently being
installed in a squeezing- ellipse rotation experiment to
demonstrate frequency-dependent squeezing for aLIGO. Lessons
learnt during the construction and operation of the in-vacuum
squeezer have helped inform the design of a frequency-independent
squeezed light source currently being installed at the LIGO
Future gravitational-wave detectors will continue to use
interferometric techniques, and will be limited by quantum noise
for the foreseeable future. To improve on thermal noise limits
and interferometer power handling, future detectors look to
cryogenic silicon as a test mass material. To take advantage of
the desirable properties of silicon, including low scatter and
absorption, a longer operating wavelength is required. The
proposed LIGO Voyager upgrade has an operating wavelength in the
2 μ m region, with the specific wavelength to be determined.
LIGO Voyager will require a squeezed light source in the 2 μ m
region to reach its design sensitivity.
We present the design, characterisation, and results of the first
squeezed light source in the 2 μ m region. Laser and detector
technologies at 2 μ m are less developed than their 1064 nm
counterparts, causing significant technical challenges. We have
measured 4.0 ± 0.2 dB of squeez- ing at 1984 nm, limited by loss
due to detector quantum efficiency. Accounting for known losses
in the system, we infer the generation of 10 dB of squeezing.
This is an important demonstra- tion of quantum noise reduction
for future detectors, and a pathfinder technology for the design
choices of LIGO Voyager. So far we have found no reason why a 2
μ m interferometer should not be feasible.
Items in Open Research are protected by copyright, with all rights reserved, unless otherwise indicated.