A Caltech Library Service

High Fidelity Probe and Mitigation of Mirror Thermal Fluctuations


Chalermsongsak, Tara (2014) High Fidelity Probe and Mitigation of Mirror Thermal Fluctuations. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/7202-WT21.


Thermal noise arising from mechanical loss in high reflective dielectric coatings is a significant source of noise in precision optical measurements. In particular, Advanced LIGO, a large scale interferometer aiming to observed gravitational wave, is expected to be limited by coating thermal noise in the most sensitive region around 30–300 Hz. Various theoretical calculations for predicting coating Brownian noise have been proposed. However, due to the relatively limited knowledge of the coating material properties, an accurate approximation of the noise cannot be achieved. A testbed that can directly observed coating thermal noise close to Advanced LIGO band will serve as an indispensable tool to verify the calculations, study material properties of the coating, and estimate the detector’s performance.

This dissertation reports a setup that has sensitivity to observe wide band (10Hz to 1kHz) thermal noise from fused silica/tantala coating at room temperature from fixed-spacer Fabry–Perot cavities. Important fundamental noises and technical noises associated with the setup are discussed. The coating loss obtained from the measurement agrees with results reported in the literature. The setup serves as a testbed to study thermal noise in high reflective mirrors from different materials. One example is a heterostructure of AlxGa1−xAs (AlGaAs). An optimized design to minimize thermo–optic noise in the coating is proposed and discussed in this work.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Thermal Noise; high reflective coatings; optical cavity
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Physics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Adhikari, Rana
Thesis Committee:
  • Adhikari, Rana (chair)
  • Chen, Yanbei
  • Libbrecht, Kenneth George
  • Weinstein, Alan Jay
Defense Date:22 May 2014
Additional Information:Thesis title in 2014 Commencement program is: High Fidelity Probe and Mitigation of Mirror Therapy Fluctuations
Funding AgencyGrant Number
Record Number:CaltechTHESIS:05282014-211250693
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:8416
Deposited By: Tara Chalermsongsak
Deposited On:30 May 2014 21:37
Last Modified:26 Oct 2021 18:26

Thesis Files

PDF - Final Version
See Usage Policy.


Repository Staff Only: item control page