764 research outputs found
Frequency stabilization of a monolithic Nd:YAG ring laser by controlling the power of the laser-diode pump source
The frequency of a 700mW monolithic non-planar Nd:YAG ring laser (NPRO)
depends with a large coupling coefficient (some MHz/mW) on the power of its
laser-diode pump source. Using this effect we demonstrate the frequency
stabilization of an NPRO to a frequency reference by feeding back to the
current of its pump diodes. We achieved an error point frequency noise smaller
than 1mHz/sqrt(Hz), and simultaneously a reduction of the power noise of the
NPRO by 10dB without an additional power stabilization feed-back system.Comment: accepted for publication by Optics Letter
The GEO 600 laser system
Interferometric gravitational wave detectors require high optical power, single frequency lasers with very good beam quality and high amplitude and frequency stability as well as high long-term reliability as input light source. For GEO 600 a laser system with these properties is realized by a stable planar, longitudinally pumped 12 W Nd:YAG rod laser which is injection-locked to a monolithic 800 mW Nd:YAG non-planar ring oscillator. Frequency control signals from the mode cleaners are fed to the actuators of the non-planar ring oscillator which determines the frequency stability of the system. The system power stabilization acts on the slave laser pump diodes which have the largest influence on the output power. In order to gain more output power, a combined Nd:YAGNd:YVO4 system is scaled to more than 22 W
Intensity and frequency noise reduction of a Nd:YAG NPRO via pump light stabilisation
We have shown that pump light intensity stabilisation of a single-mode laser diode pumped Nd:YAG non-planar ring oscillator (NPRO) results in significant intensity noise reduction of the NPRO, as well as frequency noise suppression in the same order of magnitude. This effect does not occur in conventional laser diode array pumped NPROs due to mode beating effects originating in the multi-mode pump. As opposed to individual intensity and frequency stabilisation, pump light stabilisation contributes a simplified stabilisation scheme for single-mode laser diode pumped NPROs for high precision applications
Near-field radiative heat transfer between macroscopic planar surfaces
Near-field radiative heat transfer allows heat to propagate across a small
vacuum gap in quantities that are several orders of magnitude greater then the
heat transfer by far-field, blackbody radiation. Although heat transfer via
near-field effects has been discussed for many years, experimental verification
of this theory has been very limited. We have measured the heat transfer
between two macroscopic sapphire plates, finding an increase in agreement with
expectations from theory. These experiments, conducted near 300 K, have
measured the heat transfer as a function of separation over mm to m and as
a function of temperature differences between 2.5 and 30 K. The experiments
demonstrate that evanescence can be put to work to transfer heat from an object
without actually touching it
Parallel phase modulation scheme for interferometric gravitational-wave detectors
Advanced LIGO (aLIGO) requires multiple frequency sidebands to disentangle all of the main interferometerâs length signals. This paper presents the results of a risk reduction experiment to produce two sets of frequency sidebands in parallel, avoiding mixed âsidebands on sidebandsâ. Two phase modulation frequencies are applied to separate Electro-Optic Modulators (EOMs), with one EOM in each of the two arms of a Mach-Zehnder interferometer. In this system the Mach-Zehnderâs arm lengths are stabilized to reduce relative intensity noise in the recombined carrier beam by feeding a corrective control signal back to the Rubidium Titanyl Phosphate (RTP) EOM crystals to drive the optical path length difference to zero. This setupâs use of the RTP crystals as length actuators provides enough bandwidth in the feedback to meet arm length stability requirements for aLIGO
Phase Effects in the Diffraction of Light: Beyond the Grating Equation
Diffraction gratings affect the absolute phase of light in a way that is not obvious from the usual derivation of optical paths using the grating equation. For example, consider light which encounters first one and then the second of two parallel gratings. If one grating is moved parallel to its surface, the phase of the light diffracted from the grating pair is shifted by 2Ï each time the grating is moved by one grating constant, even though the geometric path length is not altered by the motion. This additional phase shift must be included when incorporating diffraction gratings in interferometers
Characterization of thermal effects in the Enhanced LIGO Input Optics
We present the design and performance of the LIGO Input Optics subsystem as
implemented for the sixth science run of the LIGO interferometers. The Initial
LIGO Input Optics experienced thermal side effects when operating with 7 W
input power. We designed, built, and implemented improved versions of the Input
Optics for Enhanced LIGO, an incremental upgrade to the Initial LIGO
interferometers, designed to run with 30 W input power. At four times the power
of Initial LIGO, the Enhanced LIGO Input Optics demonstrated improved
performance including better optical isolation, less thermal drift, minimal
thermal lensing and higher optical efficiency. The success of the Input Optics
design fosters confidence for its ability to perform well in Advanced LIGO
High-vacuum-compatible high-power Faraday isolators for gravitational-wave interferometers
Faraday isolators play a key role in the operation of large-scale gravitational-wave detectors. Second-generation gravitational-wave interferometers such as the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) and Advanced Virgo will use high-average-power cw lasers (up to 200 W) requiring specially designed Faraday isolators that are immune to the effects resulting from the laser beam absorptionâdegraded isolation ratio, thermal lensing, and thermally induced beam steering. In this paper, we present a comprehensive study of Faraday isolators designed specifically for high-performance operation in high-power gravitational-wave interferometers
The Advanced LIGO Photon Calibrators
The two interferometers of the Laser Interferometry Gravitaional-wave
Observatory (LIGO) recently detected gravitational waves from the mergers of
binary black hole systems. Accurate calibration of the output of these
detectors was crucial for the observation of these events, and the extraction
of parameters of the sources. The principal tools used to calibrate the
responses of the second-generation (Advanced) LIGO detectors to gravitational
waves are systems based on radiation pressure and referred to as Photon
Calibrators. These systems, which were completely redesigned for Advanced LIGO,
include several significant upgrades that enable them to meet the calibration
requirements of second-generation gravitational wave detectors in the new era
of gravitational-wave astronomy. We report on the design, implementation, and
operation of these Advanced LIGO Photon Calibrators that are currently
providing fiducial displacements on the order of
m/ with accuracy and precision of better than 1 %.Comment: 14 pages, 19 figure
Search for gravitational radiation from intermediate mass black hole binaries in data from the second LIGO-Virgo joint science run
This paper reports on an unmodeled, all-sky search for gravitational waves from merging intermediate mass black hole binaries (IMBHB). The search was performed on data from the second joint science run of the LIGO and Virgo detectors (July 2009âOctober 2010) and was sensitive to IMBHBs with a range up to âŒ200 Mpc, averaged over the possible sky positions and inclinations of the binaries with respect to the line of sight. No significant candidate was found. Upper limits on the coalescence-rate density of nonspinning IMBHBs with total masses between 100 and 450 Mâ and mass ratios between 0.25 and 1 were placed by combining this analysis with an analogous search performed on data from the first LIGO-Virgo joint science run (November 2005âOctober 2007). The most stringent limit was set for systems consisting of two 88 Mâ black holes and is equal to 0.12 Mpcâ3 Myrâ1 at the 90% confidence level. This paper also presents the first estimate, for the case of an unmodeled analysis, of the impact on the search range of IMBHB spin configurations: the visible volume for IMBHBs with nonspinning components is roughly doubled for a population of IMBHBs with spins aligned with the binaryâs orbital angular momentum and uniformly distributed in the dimensionless spin parameter up to 0.8, whereas an analogous population with antialigned spins decreases the visible volume by âŒ20%
- âŠ