| Mankind is poised to directly detect gravitational waves for the first time. To improve event rates of sources these detectors will be able to measure, we will need to increase the signal-to-noise ratio of the current first generation instruments in upgraded versions. Three techniques for improving interferometer sensitivity to gravitational-wave strains are explored in this work. The first is a parallel phase modulation technique for adding two radio-frequency sidebands to the laser input of an interferometric detector like LIGO without sideband cross-products. This allows for a diagonal control matrix in the interferometer topology planned for Advanced LIGO. The stability requirements for a Mach-Zehnder interferometer with an electro-optic phase modulator in each arm is derived. We construct a prototype parallel phase modulator to test the viability of these requirements, with positive result. The second method is cryogenic cooling of optics within an interferometer by evanescent field coupling. We quantify the enhanced heat-transfer with fluctuational electrodynamics theory for a variety of dielectric materials and evaluate the effect of stratified media on thermal coupling. Noise force couplings and the implications for an advanced interferometer are discussed. In the last chapter we investigate whether a diffractive element placed in a Fabry-Perot cavity can increase the cavity bandwidth without loss of peak signal build-up. We study the interaction of such an optical resonator with a gravitational wave. A diffraction grating technique is tested and ultimately proven unable to enhance the bandwidth of gravitational wave detectors. |
