Demonstration of an optical spring in the 100g mirror regime

Optical rigidity will play an important role in future generations of gravitational wave (GW) interferometers which employ high laser power in order to reach and exceed the standard quantum limit. Several experiments have demonstrated the optical spring effect for very low weight mirror masses. In this paper we extend this to a mass and frequency regime more directly applicable to GW detectors. Using a 100 g end mirror mass we demonstrate an optical spring resonant at 500 Hz and a stiffness of 9.4 x 10(5) N m(-1). The 100 g to 1 kg mass regime may also be useful for the application as a readout mirror for optical bar or optical lever configurations.