Title: Optical Coatings for Gravitational Wave Discovery – the Thermodynamic Limit of Precision Measurement

Abstract: Gravitational wave detectors are marvels of optical precision metrology. Owing to continuing advances in sensitivity, we are now able to routinely observe binary mergers of black holes and neutron stars, which reveals much about the universe that electro-magnetic observations alone would not be able to tell. Future detectors are set to continue this trend, leading to improved observational constraints - through more observations with high signal fidelity and sampling larger volumes for source population - on theoretical descriptions of gravity, progenitor physics of binary merger events, and the equation of state of highly degenerate neutron stars. A major hurdle towards the sensitivity improvement sought by next-generation detection facilities are thermal fluctuations in mirror coatings, substrates, and suspensions: they distort laser wavefronts and generate noise, drowning weaker signals. A range of materials, deposition methods, and the use of cryogenics are being explored to reduce the impact of thermal noise and advances in modelling and simulations promise a leap in coating performance for future upgrades. In this talk I will give an overview of ground-based gravitational wave detection and highlight the limitations of current observatories due to thermodynamics. I will discuss mitigation strategies for thermal noise and showcase avenues for research into coating materials and deposition techniques.

About the Speaker: Dr. Johannes Eichholz is a Research Fellow at Australian National University in Canberra. He is currently leading efforts to develop advanced optical coatings at the thermodynamic limit of precision measurement for the LIGO gravitational wave observatory. Prior to his time at ANU, Dr. Eichholz was a postdoctoral fellow at the LIGO Laboratory at the California Institute of Technology. He earned his PhD from the University of Florida under Prof. Guido Mueller, working on digital heterodyne laser frequency stabilization for space-based gravitational wave detectors and measuring coating Brownian noise at cryogenic temperatures.