Use In Gravitational Wave Detectors Research Articles

Sequential high power laser amplifiers for gravitational wave detection.

Advanced gravitational wave detectors require highly stable, single mode, single frequency and linear polarized laser systems. They have to deliver an output power of ∼200W and need to provide suitable actuators for further stabilization via fast, low noise feedback control systems. We present such a laser system based on sequential Nd:YVO4 amplifiers and its integration into a typical laser stabilization environment. We demonstrate robust low noise operation of the stabilized amplifier system at 195 W, which makes it a viable candidate for use in gravitational wave detectors.

High-transmission fiber ring resonator for spectral filtering of master oscillator power amplifiers

We experimentally characterize a fiber-based ring resonator constructed from two commercially available 2x2 polarization-maintaining directional couplers. This ring resonator has a maximum noise suppression of 25 dB and resonant transmission of 80% at 1550 nm. Its high transmission means this ring resonator is ideally suited for the spectral filtering of master oscillator power amplifier light sources in a robust, compact, and all-fiber package. The limits of such a ring resonator for use in gravitational-wave detectors are discussed, and we show how it could be used to filter the low-power amplifier section and reduce the noise suppression requirements for the final free-space mode-cleaner.

Narrow-linewidth fiber amplifier for gravitational-wave detectors.

We report on the design and noise performance of a narrow-linewidth Yb-doped fiber amplifier emitting up to 178W at 1064nm for possible use in gravitational-wave (GW) interferometric detectors. The novel design utilizes a specialty large-mode-area gain fiber with confined-core doping and depressed cladding, followed by a smaller-core passive fiber to improve output beam quality. We show that the free-running noise of the system is equal to or better than current Advanced LIGO noise requirements. Finally, we discuss potential improvements for long-term use in GW detectors.

Thermal noise reduction and absorption optimization via multimaterial coatings

Future gravitational wave detectors (GWDs) such as Advanced LIGO upgrades and the Einstein Telescope are planned to operate at cryogenic temperatures using crystalline silicon (cSi) test-mass mirrors at an operation wavelength of 1550 nm. The reduction in temperature in principle provides a direct reduction in coating thermal noise, but the presently used coating stacks which are composed of silica (${\mathrm{SiO}}_{2}$) and tantala (${\mathrm{Ta}}_{2}{\mathrm{O}}_{5}$) show cryogenic loss peaks which results in less thermal noise improvement than might be expected. Due to low mechanical loss at low temperature amorphous silicon (aSi) is a very promising candidate material for dielectric mirror coatings and could replace ${\mathrm{Ta}}_{2}{\mathrm{O}}_{5}$. Unfortunately, such an $\mathrm{aSi}/{\mathrm{SiO}}_{2}$ coating is not suitable for use in GWDs due to high optical absorption in aSi coatings. We explore the use of a three material based coating stack. In this multimaterial design the low absorbing ${\mathrm{Ta}}_{2}{\mathrm{O}}_{5}$ in the outermost coating layers significantly reduces the incident light power, while aSi is used only in the lower bilayers to maintain low optical absorption. Such a coating design would enable a reduction of Brownian thermal noise by 25%. We show experimentally that an optical absorption of only $(5.3\ifmmode\pm\else\textpm\fi{}0.4)\text{ }\text{ }\mathrm{ppm}$ at 1550 nm should be achievable.

Remote coupling between a probe and a superconducting klystron cavity for use in gravitational wave detectors

In this work the main task was to measure the remote coupling between a probe and some niobium superconducting reentrant cavities for use in parametric transducers of gravitational wave detectors. The cavities were manufactured from RRR300 niobium and cryogenically tested to determine the electromagnetic coupling among other parameters. These cavities were also closed using a RRR300 niobium cover forming a narrow axial gap with the post top. A hole was made at the base opposite the cover in order to the probe reach the cavity. Generally, the critical coupling (β ≈ 1) is achieved with the probe inside the cavity. The mechanical connection of the probe with the transducer and the external circuit introduces an unwanted seismic noise in the transducer. The microstrip antennas have been traditionally employed to make a wireless connection. However, this study has demonstrated coupling factor β ≈ 1 with the probe moved away 4.0 mm from the cavity with a 3.0 mm diameter hole. Couplings with the probe moved away 1.0 mm and 7.0 mm from cavities with 1.5 mm and 3.5 mm diameter holes, respectively, have also been obtained. These results have revealed the influence of the hole diameter with the remote coupling between an electric field probe and the klystron mode of a superconducting reentrant cavity. Due to the practicalities, this effect may replace the microstrip antennas making it possible to implement high sensitivity parametric transducers.

Telemetry system driven by radiation power for use in gravitational wave detectors

To prevent electrical wiring from mechanically short circuiting in the high performance vibration isolators for gravitational wave detection, we designed a telemetry system. The system provides wireless signal transmission and radiation power supplies. A consideration of heat dissipation of in-vacuum electronic components is presented. The preliminary experiments demonstrated that the telemetry system is feasible.

Q factor measurements on prototype fused quartz pendulum suspensions for use in gravitational wave detectors

This paper describes measurements of the pendulum mode Q factors of prototype fused quartz test mass suspensions for use in interferometric gravitational wave detectors. Pendulums were constructed using bobs of masses ranging from approximately 12 g to 1.9 kg suspended by cylindrical fibres of standard fused quartz and Q factors obtained greater than 10 7.

Investigations into the effects of electrostatic charge on the Q factor of a prototype fused silica suspension for use in gravitational wave detectors

This paper describes some investigations into the construction of a monolithic fused silica test mass suspension for use in interferometric gravitational wave detectors. We summarize results showing that the material Q factor of standard fused quartz in the form of ribbons is of a level which makes it suitable for use as a suspension material for the test masses of long baseline gravitational wave detectors and then present measurements of the Q factor of the pendulum mode of a non-conducting mass suspended on cylindrical fibres of fused quartz. Our results show that electrostatic charging of the mass can result in a significant decrease in the pendulum mode Q factor.