1,191 research outputs found
Optimal Alignment Sensing of a Readout Mode Cleaner Cavity
Critically coupled resonant optical cavities are often used as mode cleaners
in optical systems to improve the signal to noise ratio (SNR) of a signal that
is encoded as an amplitude modulation of a laser beam. Achieving the best SNR
requires maintaining the alignment of the mode cleaner relative to the laser
beam on which the signal is encoded. An automatic alignment system which is
primarily sensitive to the carrier field component of the beam will not, in
general, provide optimal SNR. We present an approach that modifies traditional
dither alignment sensing by applying a large amplitude modulation on the signal
field, thereby producing error signals that are sensitive to the signal
sideband field alignment. When used in conjunction with alignment actuators,
this approach can improve the detected SNR; we demonstrate a factor of 3
improvement in the SNR of a kilometer-scale detector of the Laser
Interferometer Gravitational-wave Observatory. This approach can be generalized
to other types of alignment sensors
Electromagnetic corrections to p scattering length from pionic hydrogen
We derive a closed, model space independent, expression for the
electromagnetic correction factor to the scattering length
extracted from a hydrogenic atom with an extended charge to order
and in the limit of a short ranged hadronic interaction.Comment: 4 pages; PANIC02, XVIth Conference on Particles and Nuclei, Osaka, to
appear in Nuclear Physics
Hadronic Atoms and Effective Interactions
We examine the problem of hadronic atom energy shifts using the technique of
effective interactions and demonstrate equivalence with the conventional
quantum mechanical approach.Comment: 22 page latex file with 2 figure
An all-optical trap for a gram-scale mirror
We report on a stable optical trap suitable for a macroscopic mirror, wherein
the dynamics of the mirror are fully dominated by radiation pressure. The
technique employs two frequency-offset laser fields to simultaneously create a
stiff optical restoring force and a viscous optical damping force. We show how
these forces may be used to optically trap a free mass without introducing
thermal noise; and we demonstrate the technique experimentally with a 1 gram
mirror. The observed optical spring has an inferred Young's modulus of 1.2 TPa,
20% stiffer than diamond. The trap is intrinsically cold and reaches an
effective temperature of 0.8 K, limited by technical noise in our apparatus.Comment: Major revision. Replacement is version that appears in Phy. Rev.
Lett. 98, 150802 (2007
Precise calibration of LIGO test mass actuators using photon radiation pressure
Precise calibration of kilometer-scale interferometric gravitational wave
detectors is crucial for source localization and waveform reconstruction. A
technique that uses the radiation pressure of a power-modulated auxiliary laser
to induce calibrated displacements of one of the ~10 kg arm cavity mirrors, a
so-called photon calibrator, has been demonstrated previously and has recently
been implemented on the LIGO detectors. In this article, we discuss the
inherent precision and accuracy of the LIGO photon calibrators and several
improvements that have been developed to reduce the estimated voice coil
actuator calibration uncertainties to less than 2 percent (1-sigma). These
improvements include accounting for rotation-induced apparent length variations
caused by interferometer and photon calibrator beam centering offsets, absolute
laser power measurement using temperature-controlled InGaAs photodetectors
mounted on integrating spheres and calibrated by NIST, minimizing errors
induced by localized elastic deformation of the mirror surface by using a
two-beam configuration with the photon calibrator beams symmetrically displaced
about the center of the optic, and simultaneously actuating the test mass with
voice coil actuators and the photon calibrator to minimize fluctuations caused
by the changing interferometer response. The photon calibrator is able to
operate in the most sensitive interferometer configuration, and is expected to
become a primary calibration method for future gravitational wave searches.Comment: 13 pages, 6 figures, accepted by Classical and Quantum Gravit
Precise calibration of LIGO test mass actuators using photon radiation pressure
Precise calibration of kilometer-scale interferometric gravitational wave
detectors is crucial for source localization and waveform reconstruction. A
technique that uses the radiation pressure of a power-modulated auxiliary laser
to induce calibrated displacements of one of the ~10 kg arm cavity mirrors, a
so-called photon calibrator, has been demonstrated previously and has recently
been implemented on the LIGO detectors. In this article, we discuss the
inherent precision and accuracy of the LIGO photon calibrators and several
improvements that have been developed to reduce the estimated voice coil
actuator calibration uncertainties to less than 2 percent (1-sigma). These
improvements include accounting for rotation-induced apparent length variations
caused by interferometer and photon calibrator beam centering offsets, absolute
laser power measurement using temperature-controlled InGaAs photodetectors
mounted on integrating spheres and calibrated by NIST, minimizing errors
induced by localized elastic deformation of the mirror surface by using a
two-beam configuration with the photon calibrator beams symmetrically displaced
about the center of the optic, and simultaneously actuating the test mass with
voice coil actuators and the photon calibrator to minimize fluctuations caused
by the changing interferometer response. The photon calibrator is able to
operate in the most sensitive interferometer configuration, and is expected to
become a primary calibration method for future gravitational wave searches.Comment: 13 pages, 6 figures, accepted by Classical and Quantum Gravit
Squeezed light for advanced gravitational wave detectors and beyond
Recent experiments have demonstrated that squeezed vacuum states can be injected into gravitational wave detectors to improve their sensitivity at detection frequencies where they are quantum noise limited. Squeezed states could be employed in the next generation of more sensitive advanced detectors currently under construction, such as Advanced LIGO, to further push the limits of the observable gravitational wave Universe. To maximize the benefit from squeezing, environmentally induced disturbances such as back scattering and angular jitter need to be mitigated. We discuss the limitations of current squeezed vacuum sources in relation to the requirements imposed by future gravitational wave detectors, and show a design for squeezed light injection which overcomes these limitations
Benefits of Artificially Generated Gravity Gradients for Interferometric Gravitational-Wave Detectors
We present an approach to experimentally evaluate gravity gradient noise, a
potentially limiting noise source in advanced interferometric gravitational
wave (GW) detectors. In addition, the method can be used to provide sub-percent
calibration in phase and amplitude of modern interferometric GW detectors.
Knowledge of calibration to such certainties shall enhance the scientific
output of the instruments in case of an eventual detection of GWs. The method
relies on a rotating symmetrical two-body mass, a Dynamic gravity Field
Generator (DFG). The placement of the DFG in the proximity of one of the
interferometer's suspended test masses generates a change in the local
gravitational field detectable with current interferometric GW detectors.Comment: 16 pages, 4 figure
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