  We present an approach to mitigate coating thermal noise in optical cavities
by using multiple TEM spatial modes to readout and stabilize laser frequency.
With optimal weightings we synthesize a wider sampling of the mirror surface,
improving averaging of Brownian thermal fluctuation. We show thermal noise
improvement factors of 1.57, comparable to a MESA beam of a nominal 12 m
prototype cavity, and a factor 1.61 improvement over the $\textrm{TEM}_{00}$
using three modes in a 0.1 m cavity for a practical laboratory experiment:
equivalent to cooling mirrors to 120 K from room temperature.
