Lasers and optics: looking towards third generation gravitational wave detectors

Abstract

Third generation terrestrial interferometric gravitational wave detectors will likely require significant advances in laser and optical technologies to reduce two of the main limiting noise sources: thermal noise due to mirror coatings and quantum noise arising from a combination of shot noise and radiation pressure noise. Increases in laser power and possible changes of the operational wavelength require new high power laser sources and new electro-optic modulators and Faraday isolators. Squeezed light can be used to further reduce the quantum noise while nano-structured optical components can be used to reduce or eliminate mirror coating thermal noise as well as to implement all-reflective interferometer configurations to avoid thermal effects in mirror substrates. This paper is intended to give an overview on the current state-of-the-art and future trends in these areas of ongoing research and development.

Recent Advances in Resonant Waveguide Gratings

“…Moreover, they also provide lower thermal noise and lower mechanical losses thanks to their lower overall thickness . For this reason, RWG cavity mirrors have been, for example, implemented in advanced gravitational wave detectors, where the main source of noise is the cavities mirrors . Several configurations of RWG cavity mirrors have been reported, such as silicon on silica T‐like structures, monolithic single silicon crystal mirrors (as illustrated in Figure a,b) and stacks of multiple RWGs (Figure c) .…”

“…[56,342] For this reason, RWG cavity mirrors have been, for example, implemented in advanced gravitational wave detectors, where the main source of noise is the cavities mirrors. [343][344][345] Several configurations of RWG cavity mirrors have been reported, such as silicon on silica T-like structures, [57] monolithic single silicon crystal mirrors (as illustrated in Figure 17a,b) [346] and stacks of multiple RWGs (Figure 17c). [193,347] RWGs can be also be used as distributed feedback resonators in combination with planar organic thin films to engineer lasers which are more compact and easier to integrate.…”

Toward a third generation of gravitational wave observatories

“…High power fibre lasers are currently being developed but have not yet reached the performance level of solid state lasers. A current overview of available laser sources and prospects for the third generation of interferometric gravitational-wave detectors is given in [67].…”

Modal instability-suppressing, single-frequency photonic crystal fiber amplifier with 811 W output power

“…One major limitation in LIGO is shot noise, which scales inversely with the square root of power. Consequently, there is a need to develop spectrally pure diffractionlimited kW laser sources [3].…”