LIGO Document P1100125-v1

[Thesis] Design and Performance of High Laser Power Interferometers for Gravitational-wave Detection

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A prediction of Einstein's general theory of relativity,
gravitational waves (GWs) are perturbations of the flat space-time
Minkowski metric that travel at the speed of light. Indirectly
measured by Hulse and Taylor in the 1970s through the energy they
carried away from a binary pulsar system, gravitational waves have
yet to be detected directly. The Laser Interferometer
Gravitational-wave Observatory (LIGO) is part of a global network of
gravitational-wave detectors that seeks to detect directly
gravitational waves and to study their sources.

LIGO operates on the principle of measuring the gravitational wave's
physical signature of a strain, or relative displacement of inertial
masses. An extremely small effect whose biggest of expected
transient signals on Earth is on the order of one part in 10^23,
gravitational-wave strain can only be measured by detectors so
sensitive to displacement as to encounter the effects of quantum
physics. To improve their sensitivities and to demonstrate advanced
technologies, the LIGO observatories in Hanford, WA and Livingston,
LA underwent an upgrade between fall 2007 and summer 2009 called
Enhanced LIGO. This study focuses on the experimental challenges of
one of the goals of the upgrade: operating at an increased laser

I present the design and characterization of two of the
interferometer subsystems that are critical for the path towards
higher laser power: the Input Optics (IO) and the Angular Sensing
and Control (ASC) subsystems. The IO required a new design so its
optical components would not be susceptible to high power effects
such as thermal lensing or thermal beam drift. The ASC required a
new design in order to address static instabilities of the arm
cavities caused by increased radiation pressure. In all, I
demonstrate the capability of an interferometric GW detector to
operate at several times the highest of laser powers previously

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