Active damping control of a torsion pendulum by radiation pressure

In this paper, we describe the experiment of using radiation pressure to actively damp a strip torsion pendulum. The radiation source is a 1.5 W Nd:YAG laser with an actively controlled variable attenuator. By controlling the power of the laser, force of nano-newton scale can be generated and used to damp the resonant oscillation of the pendulum. We also quantitatively measured the force due to the radiation pressure. The result is in good agreement with the theoretical prediction.