Mirrors Coating
Key challenges in a nutshell
- Develop crystalline oxide mirror coatings
- Highly uniform coatings (~ 0.1%) over large areas such as on 300mm wafers
- Explore layer transfer and wafer bonding processes
- 4 ✕ reduction in coating loss compared to SiO2 and TiO2:Ta2O5 in Adv. LIGO/Virgo (for 12 cm beam)
Short description of the technology
Highly-reflective coatings are obtained by stacking of many layers, usually using two materials with different refractive index n
➢ optical layer thickness: quarter of a wavelength (= higher n → thinner layer)
Example: amorphous SiO2 (n=1.45) and Ta2O5 (n=2.05)
➢ ~38 layers needed for highly reflective ETMs of R = 99.9995%
➢ light intensity reduces with every layer pair
State of the Art: technology in existing gravitational wave detectors / TRL
Coating thermal noise (CTN)is alimiting noise source and needs to be reduced. It is:
- frequency dependent (high at low frequency)
- lower for larger beams
- temperature dependent
- determined by elastic properties / mechanical loss factor (coating and substrate)
- research aims to improve SiO2/Ta2O5 through doping, nanolayers, replacing Ta2O5 by other materials like GeO2, amorphous Si, etc.
Intended use in the frame of the Einstein Telescope
To improve the telescope performance, two approaches are followed in parallel for the mirrors. First, the diameter (d) of the mirror bodies is increased since noise scales with . The second path is to significantly improve the CTN by lowering the temperature of operation as well as to significantly lower (~ factor of 10) the mechanical losses of the coatings.
Improvements needed: Technological challenge for the Einstein Telescope
ET-HF:
○ Same wavelength, substrate material and temperature as LIGO and Virgo detectors
○ Challenge: Upscaling coating diameter by almost a factor of two (bubble- and defect-free)
ET-LF:
○ Active research areas within extended EMR region: nanolayers, multi-material coatings and crystalline coatings
Economic perspectives of participation beyond the ET applications
Proposals for joint ET-relevant R&D activities / new business applications: To be filled in on the base of the companies’ proposals
Related projects and labs
none
Ongoing and future procurements
You can find all procurements and calls for tender in the context of the Interreg EMR projects “E-TEST” and “ET2SMES” on the central “Procurements” landingpage of the E-TEST project.
Business Development contacts
Peter Gier
AGIT DE – p.gier@agit.de
Matthias Grosch
NMWP.NRW DE – matthias.grosch@nmwp.de
Michel Stassart
Skywin BE – michel.stassart@skywin.be
Maxime Corvilain
POM Limburg BE – maxime.corvilain@pomlimburg.be
René Kessen
LIOF NL – rene.kessen@liof.nl
Technology contact
Jean-Pierre Locquet
KU Leuven – jeanpierre.locquet@kuleuven.be