New method to measure the angular antispring effect in a Fabry–Perot cavity with remote excitation using radiation pressure

•A method to measure an angular antispring effect on a suspended mirror was proposed.•Remote excitation on the mirror with radiation pressure of resonant light is used.•This method provides better measurement accuracy compared with the previous method.

In experiments with Fabry–Perot cavities consisting of suspended mirrors, an angular antispring effect on the mirror of the cavity is caused by radiation pressure from resonant light in the cavity. A new method was invented to measure the effect precisely with remote excitation on the mirror using the radiation pressure. This method was found to be available for the suspended 23 mg mirror and improved the measurement accuracy by a factor of two, compared with the previous method. This result leads to stable control systems to eliminate the angular instability of the mirror caused by the effect.