7 research outputs found
Adaptive thermal compensation of test masses in advanced LIGO
As the first generation of laser interferometric gravitational wave detectors
near operation, research and development has begun on increasing the
instrument's sensitivity while utilizing the existing infrastructure. In the
Laser Interferometer Gravitational Wave Observatory (LIGO), significant
improvements are being planned for installation in ~2007, increasing strain
sensitivity through improved suspensions and test mass substrates, active
seismic isolation, and higher input laser power. Even with the highest quality
optics available today, however, finite absorption of laser power within
transmissive optics, coupled with the tremendous amount of optical power
circulating in various parts of the interferometer, result in critical
wavefront deformations which would cripple the performance of the instrument.
Discussed is a method of active wavefront correction via direct thermal
actuation on optical elements of the interferometer. A simple nichrome heating
element suspended off the face of an affected optic will, through radiative
heating, remove the gross axisymmetric part of the original thermal distortion.
A scanning heating laser will then be used to remove any remaining
non-axisymmetric wavefront distortion, generated by inhomogeneities in the
substrate's absorption, thermal conductivity, etc. A proof-of-principle
experiment has been constructed at MIT, selected data of which are presented.Comment: 11 pages, 7 figures, submitted to Classical and Quantum Gravit
-BaBO deep UV monolithic walk-off compensating tandem
The generation of watt-level cw narrow-linewidth sources at specific deep UV
wavelengths corresponding to atomic cooling transitions usually employs
external cavity-enhanced second-harmonic generation (SHG) of moderate-power
visible lasers in birefringent materials. In this work, we investigate a novel
approach to cw deep-UV generation by employing the low-loss BBO in a monolithic
walkoff-compensating structure [Zondy {\it{et al}}, J. Opt. Soc. Am. B
{\bf{20}} (2003) 1675] to simultaneously enhance the effective nonlinear
coefficient while minimizing the UV beam ellipticity under tight focusing. As a
preliminary step to cavity-enhanced operation, and in order to apprehend the
design difficulties stemming from the extremely low acceptance angle of BBO, we
investigate and analyze the single-pass performance of a mm monolithic
walk-off compensating structure made of 2 optically-contacted BBO plates cut
for type-I critically phase-matched SHG of a cw nm dye laser. As
compared with a bulk crystal of identical length, a sharp UV efficiency
enhancement factor of 1.65 has been evidenced with the tandem structure, but at
nm from the targeted fundamental wavelength, highlighting the
sensitivity of this technique when applied to a highly birefringent material
such as BBO. Solutions to angle cut residual errors are identified so as to
match accurately more complex periodic-tandem structure performance to any
target UV wavelength, opening the prospect for high-power, good beam quality
deep UV cw laser sources for atom cooling and trapping.Comment: 21 pages, 8 figures, to appear in Opt. Commu
Mechanical loss factors of materials and suspension systems for advanced gravitational wave detectors
The thermal noise of the fused silica test masses and their metal suspension fibers presents a significant limitation to the sensitivity of interferometric gravitational wave detectors. Advanced suspensions are likely to require the use of materials of substantially lower mechanical loss. Here we present measurement of the mechanical loss of fused quartz elements suitable for use as suspension fibers in an advanced suspension system and summarize measurements of the mechanical and optical loss of potential replacement test mass materials
LIGO optics: initial and advanced
The LIGO project has completed the installation of large fused silica optical components in the vacuum systems of its observatories. Commissioning work on the Hanford 2 km interferometer has determined an upper limit to the optics losses, allowing comparison with design and pre-installation testing. Planning and development of sapphire optics for the next generation, advanced LIGO detector is now underway, including polishability, optical homogeneity, absorption, and birefringence. The advanced optics development also includes research aimed at lowering coating loss