Conveners
Coating thermal noise Workshop: Hour 1
- Gianpietro Cagnoli (ILM-UCBL)
- Stuart Reid (SUPA, University of Strathclyde)
- Elisabetta Cesarini (ROMA2)
Coating thermal noise Workshop: Hour 2
- Gianpietro Cagnoli (ILM-UCBL)
- Elisabetta Cesarini (ROMA2)
- Stuart Reid (SUPA, University of Strathclyde)
Coating thermal noise Workshop: Hour 3-4
- Stuart Reid (SUPA, University of Strathclyde)
- Elisabetta Cesarini (ROMA2)
- Gianpietro Cagnoli (ILM-UCBL)
To realize the design sensitivity of Advanced LIGO+, about a factor of two in coating thermal noise reduction is required. For ET-HF and the initial Cosmic Explorer design very similar coating thermal noise levels are assumed. Another requirement on the highly-reflective mirror coatings is low optical absorption of <1ppm which is challenging to meet.
Multimaterial designs allow for a...
A cryogenic mechanical loss measurement setup built at Stanford University can operate from room temperature down to at least 12K. The experimental method described is based on actuation of a Si oscillator and measurement of its quality factor (Q-factor). The film’s mechanical loss can be obtained using the Q-factors of coated and uncoated resonators. Experimental results obtained for several...
SiN has emerged as one of the most promising materials for the next-generation optical coatings in the mirrors of GW detectors. Optical absorption is currently one of the most critical parameters affecting the performances of SiN films, as a very low absorption is required for GW applications; optical absorption may arise from a variety of causes, including non-ideal stoichiometry and...
Silicon nitride (SiNx) is a well-known coating material, with a relatively high refractive index and very low mechanical loss. In this talk, we will present the development history of ion-beam sputtered amorphous SiNx coatings for gravitational-wave detectors at the Laboratoire des Matériaux Avancés (LMA-IP2I). As this research and development activity is still ongoing to date, we will present...
Brownian noise in the current second generator detectors is limited by the internal mechanical energy dissipation of the high index material composing the dielectric reflector stack. One promising alternative to the currently used titania-doped tantala is a mixture of titania and germania. We report here the status of the research on this new material, estimates of the achievable improvements...
The Gentle Nodal Suspension (GeNS) has become the most common technique for measuring coating mechanical dissipation, showing an unprecedented result repeatability on disk shaped substrates. GeNS gives the possibilities to perform measurement so accurate that it is possible to follow even tiny changes in the sample mechanical behavior. The high level of sensitivity makes some new systematic...
The observational horizon of interferometric gravitational wave (GW) detectors is limited by thermal noise in the coating at mid-range frequency, where first GW signals have been detected and many others are expected. The main responsible are the intrinsic dissipations, intimately linked to the inelastic behaviour of the amorphous coating materials. This behaviour is generally explained by the...
GW detector highly reflective coatings are obtained by alternate layers of material with different refractive indexes. Brownian thermal noise associated with the coating stack, limits the mid-frequency region of the GW detector designed sensitivity. Thermal noise reduction can be achieved minimizing the overall thickness of the stack, increasing the refractive index contrast . Fluoride’s...
The structure of ternary coatings featuring minimum thermal (Brownian) noise under prescribed transmittance and absorbance constraints is investigated and found to consist of a few tapered quasi-Bragg triplets on top of an almost fixed-thickness stack of wuasi Bragg doublets using the highest contrast material pair.
The noise reduction of coatings based on aSi, TiO2::Ta2O5 and SiO2 as well as...
Substrate-transferred crystalline coatings have demonstrated low thermal noise and excellent optical properties in multiple precision optics applications. The primary challenge in implementing these single-crystal gallium arsenide / aluminum gallium arsenide multilayers in terrestrial interferometric gravitational-wave detectors is the necessity to scale the size of the coatings to ≥ 30 cm in...
Accumulated charge on vacuum mirrors can cause degradation of the signal-to-noise ratio in opto-mechanical measurements due to electrostatic coupling of the surface charge to the environment. A conductive film with minimal optical absorption and scattering can dissipate the charge without altering the optical performance of high reflectivity mirrors. We present Aluminum doped ZnO coatings...
