Source of systematic modeling error in mirror curvature change versus power

Identify and explain the source of the observed systematic discrepancy between the measured mirror radius‑of‑curvature change and the theoretical thermoelastic model across low and high circulating powers in the previous prototype cavity, and refine the model to remove the bias.

Background

The measured change in mirror curvature with circulating power was fit with the proposed self‑consistent thermoelastic model. While broadly matching, the fit underestimates curvature change at both low and high power.

Pinpointing the origin of this systematic residual and correcting the model will improve predictions of focal waist and intensity limits, and guide mirror substrate/coating choices.