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During the Initial and Enhanced LIGO phases, a half-length interferometer operated in parallel with the main interferometer. For this 2 km interferometer, the Fabry–Pérot arm cavities had the same optical finesse, and, thus, half the storage time as the 4 km interferometers. With half the storage time, the theoretical strain sensitivity was ...
A laser is divided into two beams by a beam splitter tilted by 45 degrees. The two beams propagate in the two perpendicular arms of the interferometer, are reflected by mirrors located at the end of the arms, and recombine on the beam splitter, generating interferences which are detected by a photodiode. An incoming gravitational wave changes ...
Adhikari has been involved in the construction and design of gravitational-wave detectors since 1997. [19] He started working on laser interferometers as a graduate student at MIT, with a particular focus on the variety of noise sources, feedback loops and subsystems, [20] [21] and helped to reduce the noise in all 3 of the LIGO interferometers while working on the Livingston interferometer.
The Laser Interferometer Gravitational-Wave Observatory (LIGO) uses two 4-km Michelson–Fabry–Pérot interferometers for the detection of gravitational waves. [38] In this application, the Fabry–Pérot cavity is used to store photons for almost a millisecond while they bounce up and down between the mirrors.
The result is an interferometer that exhibits the stability of the Sagnac topology while being insensitive to rotation. [46] The Laser Interferometer Gravitational-Wave Observatory (LIGO) consisted of two 4-km Michelson–Fabry–Pérot interferometers, and operated at a power level of about 100 watts of laser power at the beam splitter. After ...
Laser resonators are often described as Fabry–Pérot resonators, although for many types of laser the reflectivity of one mirror is close to 100%, making it more similar to a Gires–Tournois interferometer. Semiconductor diode lasers sometimes use a true Fabry–Pérot geometry, due to the difficulty of coating the end facets of the chip.
The space frame was mounted on an air bearing surrounding a central mast. An arm extended from the central mast, which had a parabolic track on the bottom side. The parabolic track was shaped by a laser metrology system that made use of the fact that a parabola is the locus of points equidistant from the focal point and a directrix line.
To avoid noise on the interferometer and have a low probability of emitting more than one photon each time, a very low absolute temperature for the experiment is needed, on the order of 60 μK. For similar reasons, and to avoid decoherence , the experimental device has to be in ultra-high vacuum conditions.