Laser Interferometer Gravitational Wave Observatories (LIGO) are supported by the National Science Foundation, USA and operated by Caltech and MIT.
LIGO is a world-leading observatory designed to detect gravitational waves from the most violent events in the Universe. LIGO and the associated collaboration, involving 37 researchers from 9 Indian institutions, is known for the first direct detection of Gravitational Waves. This opened a completely new window with which scientists are starting to probe hitherto unexplored phenomena such as the formation of black holes, exploding neutron stars, witnessing the birth of our Universe and so on. This enriches multi-messenger astronomy complementing the conventional means of observing and studying the Universe with telescopes using light. The physical measurements required for gravitational wave detection are arguably the most precise ever made, and they involve cutting-edge technologies that have many day-to-day applications.
LIGO-India, an ongoing enterprise to set up a new gravitational wave detector on Indian soil, is a mega-science project jointly funded by the DAE and DST. With this addition to the existing network of detectors globally, we will dramatically increase the sensitivity and positional accuracy with which gravitational events will be detected. India will provide the site, vacuum system and other infrastructure required to house and operate the interferometer, and manpower, materials and supplies for installation, commissioning and operations. Presence of such a world-leading facility in India will inspire and attract generations of students to pursue challenging careers in science, technology and innovation.
DAE: Departments of Atomic Energy
DST: Department of Science and Technology
During its development, LIGO has already spawned innovative technologies in diverse areas as described below:
Nonlinear optical materials used in the area of high-performance optics and optical metrology require precise measurement of properties such as absorption losses and damage thresholds. One of the most successful approaches developed in Advanced LIGO (aLIGO) to characterize these materials is the Photothermal Common Path Interferometry.
Adaptive laser beam shaping
High power modulator
Adaptive beam shaping of the high-power laser beams had to be developed due to the extreme sensitivity to wavefront distortions encountered in LIGO. The thermal compensation system developed for correcting these distortions uses ring-heaters on the outer barrel of the mirrors to correct their radius of curvature and a CO2 laser to heat a transparent compensation plate.
High-power laser beams require the phase modulation of the laser field. Previous commercial phase modulators were incapable of handling laser powers in excess of a few watts without beam heating resulting in thermo-optic distortion of the laser beam. Our newly developed high-power electro-optical modulators (EOM) can handle up to 200W of continuous laser power with no beam degradation. Our design was also proven to reduce the spurious polarization and amplitude modulation of phase modulators by several orders of magnitude while eliminating the very strict alignment tolerances of earlier modulators.
Pound-Drever-Hall Locking demonstrated that high-frequency phase modulation of the light directed toward the optical cavity, together with coherent detection of the light reflected from the optical cavity, resulting in the generation of a useful error signal over a wide detuning bandwidth around the cavity resonance. It was found that these features could be effectively used to implement very wideband and high-gain servo control. The technique is now not only widespread in many fields, including spectroscopy, chip and reticule inspection, precision standards definition, optical frequency standards, spaceborne metrology applications, development and testing of ultra-low-loss mirrors, frequency reference cavities, fiber optic sensing and nonlinear laser frequency conversion but also underpins almost all advances in frequency metrology, fundamental measurement, and any field in which lasers must be controlled in frequency, such as ultra-stable optical clocks, and dissemination of laser frequency standards.
Edge pumped zig-zag slab laser is based on conduction cooling and a novel pumping geometry called transverse or edge pumping. The edge-pumping geometry decouples the cooling and optical pumping interfaces, simplifying the laser-head design. The advantages of this design include efficient pump light absorption, acceptance of high-numerical-aperture pump sources, uniform conductive cooling, and scalability to a higher power.
Vacuum cable clamp
Interferometric displacement sensor
When using simple interferometers as displacement sensors, they require that the mirror whose displacement is to be sensed must be aligned in pitch and yaw with respect to the light beam, limited in their dynamic range, and the sensor must have very good internal mechanical and thermal stability consistent with the required displacement sensitivity. An interferometric displacement sensor was developed and it uses homodyne interferometry to overcome the low dynamic range problem; a compact and very stiff mechanical design using low CTE material to achieve stability and a clever optical design to achieve a tolerance against mirror pitch and yaw misalignment of more than 1 degree.
Oxide bonding techniques
Oxide bonding techniques for joining silicon carbide, with high mechanical strength and stability, are required for use in the fabrication of optical systems used in space-based applications such as telescope assemblies and optical benches. The original technique of hydroxy-catalysis, also known as "silicate bonding” was invented for the purpose of joining the fused silica pieces. LIGO is making use of a variant of this technique to fabricate the quasi-monolithic fused silica suspensions now being used for Advanced LIGO. This technique was selected for use in ground-based gravitational wave detectors because of its high strength with very thin bonding layers combined with a low mechanical loss, thus maintaining low thermal noise.
Fast chirp transform
Blind data search method
Distributed identity management
Managing multiple online accounts and keeping them safe has become increasingly difficult and challenging. Nowadays, scientists work in large international collaborations and use many online software or tools. Each of these tools requires a separate set of credentials and a whole new system has to be set up, maintained and dealt with for user accounts and security-related issues. The tools of "federated identity management" software like Shibboleth from the Internet2 project remove this burden and enable efficient online collaboration by allowing users a single ID and password to access resources both within and outside an organization. LIGO is leading the effort to bring the benefits of federated identity management to large scientific research organizations and projects. This will also enable scientists the power to quickly create their own virtual groups and to manage user access to web pages, wikis, email lists, software repositories and other tools needed to support their projects.
Chennai Mathematical Institute (CMI), Chennai
Directorate of Construction, Services & Estate Management (DCSEM), Mumbai**
Indian Institute of Science Education and Research (IISER) - Kolkata, Kolkata
Indian Institute of Science Education and Research (IISER)- Pune, Pune
Indian Institute for Technology (IIT) - Bombay, Mumbai
Indian Institute for Technology (IIT) - Gandhinagar, Gandhinagar
Indian Institute for Technology (IIT) - Hyderabad, Hyderabad
Indian Institute for Technology (IIT) - Madras, Chennai
Institute of Advanced Research (IAR), Gandhinagar
Institute for Plasma Research (IPR), Gandhinagar**
International Centre for Theoretical Sciences (ICTS), Bengaluru
Inter-University Centre for Astronomy & Astrophysics (IUCAA), Pune**
Raja Ramanna Centre for Advanced Technology (RRCAT), Indore **
Tata Institute of Fundamental Research (TIFR), Mumbai
** Lead institutions responsible for the construction, commissioning and operation of LIGO-India
Indian institutions such as IUCAA, RRCAT, IPR, and DCSEM are in the process of discussing with industries/companies and identifying them which will help in developing the technological capability needed for building detector for LIGO-India
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