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Gravitational Waves
LIGO & other (GW) observatories

Most of us have by now heard of gravitational waves as predicted by Einstein. - Note: "Gravity Wave" is a very different topic In 2017, the Nobel Prize in Physics was awarded to Rai Weiss, Kip Thorne and Barry Barish, "for decisive contributions to the LIGO detector ... Unfortunately, this web page is quite U.S. centric. The (in alphabetical order) British, Germans, Italians, Japanese, and others have made significant contributions and (currently) smaller excellent interferometers which help technical development for all. About current activity from the web sites of the various gravitational wave ( GW ) centers. ( O3 - starting April 1 2019) Various web sites GEO-600, KAGRA, LIGO, Virgo, - and Wikipedia article and Twitter posting Information is available in the LIGO magazine. The URL is https://ligo.org/magazine/LIGO-magazine-issueNN.pdf where the NN is the issue number. - For easier access you can click on the following issue numbers: 13, 14, 15, 16, 17, 18, (the following ?future? issues are not available as of July 1,2021) 19, 20 The latest KAGRA information.

Gravitational Waves

as of July 12, 2021

LIGO and other Gravitational Wave observatories (using GOOGLE Maps)

LIGO, Livingston, LA

LIGO, Hanford, Wash

VIRGO, Pisa, Italy

GEO-600, Hanover, Gr

TAMA300, Tokyo, Japan

KAGRA, under Mount Ikeno Kamioka, Japan

Gravitational Waves for a General Audience

• The Absurdity of Detecting Gravitational Waves
• Ray Weiss, Sackler Lecture: Feb 15, 2018
• Nobel Lectures: Physics 2017: 1st Rainer Weiss, 2nd Barry Barish, 3rd Kip Thorne
• A talk about the physical challenges by Kip Thorne, Bollzano Lecture, at Prague, Czech Republic, May 15, 2019
• Exploring the Universe with Gravitational Waves, by Kip Thorne - Jun 22, 2016
• Brian Greene's Gravitational Waves: A New Era of Astronomy Begins great panel discussion, Jun 22, 2016
• Suspending the test masses (with mirrors)
• Vibration Isolation from CalTech
• Copy of "First cosmic event seen in gravitational waves and light" LIGO and optical telescope

Gravitational Waves for a more technical audience

• "Control Systems and Laser Frequency Stabilization" by Erik Black
  - serious control theory for lasers, 1st of two parts, for LIGO
  - - each part = 45 min
  - Laplace and Fourier transforms, convolution theorem, etc.
  - Nyquist diagram, gain and phase margins, Bode plots, ;--)
  - Pound-Drever-Hall Locking
• Physical Layout (2015) - Six suspended masses with full and partial reflectors -
• Phys 237: Gravitational Waves with Kip Thorne, Lec 1, Lec 2, Lec 3, Lec 3b, Lec 4, and so forth
• Properties of the Binary Black Hole Merger GW150914, the many input variables and calculations giving final results -
• Quantum expander for gravitational-wave observatories (free download of report)

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LIGO

• Versions of Gravitational Wave detectors
  1. Weber bar aluminum "bar" with strain detectors glued on it
     Not sensitive enough - but inspired a lot of people !
  2. Interferometer, with reflective cavities
     • early small test and demo interferometers
     • first LIGO
     • Advanced LIGO
     • A+, Enhancing Advanced LIGO -G1601435 paper
     • LIGO Voyager -G1700848 paper
• Introductory
  • I've gone to a number of LIGO lectures, and picked up some fun documentation

    Handouts 1st-GW150914.pdf - Was Einstein right about strong gravity? Using Gravitational Waves ... 2nd-GW151226.pdf - GW151226: Observation of Gravitational Waves ... ObservationGW.pdf - General, Observation of Gravitational Waves ... Quantum Enhanced LIGO Detector Sets New Sensitivity Record Research paper Stretched.pdf - If light waves are stretched by gravitational waves, how ... Video �100 Years of Gravitational Waves: The Observation of a Binary Black Hole Collision" - Rainer Weiss, (MIT) Sept 20, 2017 Joint Detection of Gravity Waves and Light from the Binary Neutron Star Merger GW170817 Edo Berger Sackler Lecture: Exploration of the Universe with Gravitational Waves - Rainer Weiss, (MIT) Feb 15, 2018 - he stresses thinking of these as phase modulated side bands at the frequency of the gravitational wave.
• Financing, Organization
  • LIGO Richard Isaacson - NSF - long term funding, Marcel Bardon boss,
    "Detecting gravitational waves takes a team and long-game perspective"
• Nobel Prize Lectures
  • "History" Nobel Lecture: Rainer Weiss, Nobel Prize in Physics 2017
  • "Present" Nobel Lecture: Barry C. Barish, Nobel Prize in Physics 2017
  • "Future" Nobel Lecture: Kip Thorne, Nobel Prize in Physics 2017
• Frequency Response, and low noise frequencies
• Light
  • laser - why this frequency
    • Uses 1064 nm light from a Nd:YAG laser.
  • stabilization of laser
    • The Pound�Drever�Hall (PDH) technique is a widely used and powerful approach for stabilizing the frequency of light emitted by a laser by means of locking to a stable cavity.
    • from CalTech Stabilized high-power laser system forthe gravitational wave detector advancedLIGO - 2012
      also, by Evan Hall Laser Frequency and Intensity Stabilization for Advanced LIGO (?2016??)
    • LIGO's Laser
  • squeezed light
    • Squeezed coherent state Wikipedia
    • Squeezed states of light - RP Photonics
    • Squeezed light - Vladimir Braginsky - variation of radiation pressure on the mirror variation diffraction pattern - pair of photons out of phase ... something
      A memorial to Vladimir Braginsky, who among other things, searched for "underwater rocks" that might limit LIGO.
    • GEO600 has been improving the science and art of squeezed light as part of their research to lower noise in interferometers.
    • A 1997 paper in Nature Measurement of the quantum states of squeezed light
• LIGO Techie sites
  • Caltech's
  • MIT's
  • "Sister facilities"
    • VIRGO Italy
    • GEO600 Germany
    • TAMA300 Japan
    • LIGO-India India
    • LISA-ESA, LISA-NASA
• Observing environment and "Veto" intervals of time
• People
• Transverse waves
• Test masses and Suspensions
  • "Mirrors That Hang on Glass Threads" video
  • "Active vibration isolation using a Suspension Point Interferometer" - .pdf - 2006
  • "Active vibration isolation using a Suspension Point Interferometer" - slides of lecture - 2004
• Ultimate limits of Gravitational Wave detection on earth, turbulent air masses, ...
  - Bury deep as in Japan ?

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• Current status
  The two LIGO sites were shut down (October 2017) for the squeezed light upgrade I don't understand, And ?other things ... Hope they return to service late 2018.
  Update (from web page on June 24, 2021)
  "LIGO, Virgo and Kagra Observing Run Plans - News Release � November 17, 2020
  "The LIGO Laboratory Operations Management Team has reviewed procurements and operational protocols required for the Detector Improvement and A+ modifications in preparation for O4. We currently project that the O4 observing run will not begin before June 2022, due to key procurement delays. A number of significant modifications to vacuum and detector systems during autumn 2020 will refine our understanding of COVID impacts on our schedule. We will give a revised projection in March 2021 of the O4 start date, based on lessons learned."

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Notes from Ray Weiss's lecture

1. this is just like the Heisenberg microscope that you learned about in quantum mechanics, but not with an electron, but with a 40 Kg Test Mass.

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