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Savage R.L.,LIGO Laser Interferometer Gravitational-Wave Observatory
2016 Conference on Lasers and Electro-Optics, CLEO 2016 | Year: 2016

LIGO's recent observation of a binary black hole merger initiated the era of gravitational wave astronomy. This talk will give an overview of Advanced LIGO, the recently completed observing run, and prospects for future observations. © 2016 OSA.


Harms J.,California Institute of Technology | O'Reilly B.,LIGO Laser Interferometer Gravitational-Wave Observatory
Bulletin of the Seismological Society of America | Year: 2011

In April of 2009 a seismic survey utilizing explosive charges took place in Livingston parish, Louisiana. The area of the survey encompassed the location of the Laser Interferometer Gravitational-Wave Observatory (LIGO) Livingston interferometer. In this paper, we present an analysis of seismic data recorded with three of the LIGO seismometers and a geophone array that was deployed during the time of the survey. In particular, the geophone-array data are used to study the propagation of surface waves, whereas first-arrival measurements with the LIGO seismometers provide estimates of the speed of compressional seismic waves as a function of depth. We find that fundamental Rayleigh waves have a speed close to 205 m/s consistent with results from previous borehole tests and that speed of compressional waves is 1650 m/s at 25 m depth, increasing to 2300 m.s at 1 km depth. Blast spectra are further investigated to determine the Q value of the ground medium experienced by Rayleigh waves (f > 1 Hz) and body waves deeper underground. The estimated Q value is approximately 50 for the surface waves and exceeds a value of 190 for body waves propagating at depths below 100 m.


Izumi K.,LIGO Laser Interferometer Gravitational-Wave Observatory | Sigg D.,LIGO Laser Interferometer Gravitational-Wave Observatory | Barsotti L.,Massachusetts Institute of Technology
Optics Letters | Year: 2014

High finesse optical cavities are an essential tool in modern precision laser interferometry. The incident laser field is often controlled and stabilized with an active feedback system such that the field resonates in the cavity. The Pound-Drever-Hall reflection locking technique is a convenient way to derive a suitable error signal. However, it only gives a strong signal within the cavity linewidth. This poses a problem for locking an ultra-narrow linewidth cavity. We present a novel technique for acquiring lock by utilizing an additional weak control signal, but with a much larger capture range. We numerically show that this technique can be applied to the laser frequency stabilization system used in the Laser Interferometric Gravitational-wave Observatory (LIGO), which has a linewidth of 0.8 Hz. This new technique will allow us to robustly and repeatedly lock the LIGO laser frequency to the common mode of the interferometer. © 2014 Optical Society of America.


Fritschel P.,Massachusetts Institute of Technology | Evans M.,Massachusetts Institute of Technology | Frolov V.,LIGO Laser Interferometer Gravitational-Wave Observatory
Optics Express | Year: 2014

Balanced homodyne detection is typically used to measure quantum-noise-limited optical beams, including squeezed states of light, at audio-band frequencies. Current designs of advanced gravitational wave interferometers use some type of homodyne readout for signal detection, in part because of its compatibility with the use of squeezed light. The readout scheme used in Advanced LIGO, called DC readout, is however not a balanced detection scheme. Instead, the local oscillator field, generated from a dark fringe offset, co-propagates with the signal field at the anti-symmetric output of the beam splitter. This article examines the alternative of a true balanced homodyne detection for the readout of gravitational wave detectors such as Advanced LIGO. Several practical advantages of the balanced detection scheme are described. © 2014 Optical Society of America.


Oelker E.,Massachusetts Institute of Technology | Barsotti L.,Massachusetts Institute of Technology | Dwyer S.,LIGO Laser Interferometer Gravitational-Wave Observatory | Sigg D.,LIGO Laser Interferometer Gravitational-Wave Observatory | Mavalvala N.,Massachusetts Institute of Technology
Optics Express | Year: 2014

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. © 2014 Optical Society of America.


Miller J.,Massachusetts Institute of Technology | Barsotti L.,Massachusetts Institute of Technology | Vitale S.,Massachusetts Institute of Technology | Fritschel P.,Massachusetts Institute of Technology | And 2 more authors.
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

In the coming years, the gravitational-wave community will be optimizing detector performance to target a variety of astrophysical sources which make competing demands on detector sensitivity in different frequency bands. In this paper we describe a number of technologies that are being developed as anticipated upgrades to the Advanced LIGO detectors and quantify the potential sensitivity improvement they offer. Specifically, we consider squeezed light injection for the reduction of quantum noise, detector design and materials changes which mitigate thermal noise and mirrors with significantly increased mass. We explore how each of these technologies impacts the detection of the most promising gravitational-wave sources and suggest an effective progression of upgrades which culminates in a twofold improvement in broadband sensitivity. © 2015 American Physical Society.


Dwyer S.,LIGO Laser Interferometer Gravitational-Wave Observatory | Sigg D.,LIGO Laser Interferometer Gravitational-Wave Observatory | Ballmer S.W.,Syracuse University | Barsotti L.,Massachusetts Institute of Technology | And 2 more authors.
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

Twenty years ago, construction began on the Laser Interferometer Gravitational-wave Observatory (LIGO). Advanced LIGO, with a factor of 10 better design sensitivity than Initial LIGO, will begin taking data this year, and should soon make detections a monthly occurrence. While Advanced LIGO promises to make first detections of gravitational waves from the nearby universe, an additional factor of 10 increase in sensitivity would put exciting science targets within reach by providing observations of binary black hole inspirals throughout most of the history of star formation, and high signal to noise observations of nearby events. Design studies for future detectors to date rely on significant technological advances that are futuristic and risky. In this paper we propose a different direction. We resurrect the idea of using longer arm lengths coupled with largely proven technologies. Since the major noise sources that limit gravitational wave detectors do not scale trivially with the length of the detector, we study their impact and find that 40 km arm lengths are nearly optimal, and can incorporate currently available technologies to detect gravitational wave sources at cosmological distances (z ≳ 7). © 2015 American Physical Society.


Dwyer S.,LIGO Laser Interferometer Gravitational-Wave Observatory | Ballmer S.W.,Syracuse University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

Radiative losses have traditionally been neglected in the calculation of thermal noise of transmissive optical elements because for the most commonly used geometries they are small compared to losses due to thermal conduction. We explore the use of such transmissive optical elements in extremely noise-sensitive environments such as the arm cavities of future gravitational-wave interferometers. This drives us to a geometry regime where radiative losses are no longer negligible. In this paper we derive the thermorefractive noise associated with such radiative losses and compare it to other known sources of thermal noise. © 2014 American Physical Society.


Dwyer S.,LIGO Laser Interferometer Gravitational-Wave Observatory
Physics Today | Year: 2014

You cant beat the Heisenberg uncertainty principle, but you can engineer systems so that most of the uncertainty is in the variable of your choice. Doing so can improve the precision of delicate measurements.


Meadors G.D.,University of Michigan | Kawabe K.,LIGO Laser Interferometer Gravitational-Wave Observatory | Riles K.,University of Michigan
Classical and Quantum Gravity | Year: 2014

LIGO, the Laser Interferometer Gravitational-wave Observatory, has been designed and constructed to measure gravitational wave strain via differential arm length. The LIGO 4 km Michelson arms with Fabry-Perot cavities have auxiliary length control servos for suppressing Michelson motion of the beam-splitter and arm cavity input mirrors, which degrades interferometer sensitivity. We demonstrate how a post facto pipeline improves a data sample from LIGO Science Run 6 with feedforward subtraction. Dividing data into 1024 s windows, we numerically fit filter functions representing the frequency-domain transfer functions from Michelson length channels into the gravitational-wave strain data channel for each window, then subtract the filtered Michelson channel noise (witness) from the strain channel (target). In this paper we describe the algorithm, assess achievable improvements in sensitivity to astrophysical sources, and consider relevance to future interferometry. © 2014 IOP Publishing Ltd.

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