Proof-of-principle demonstration of a polarization-circulation speed meter

We present the first experimental implementation of a polarization-circulation speed meter. In our experiment, the interferometer was reduced to a single-cavity configuration with all mirrors fixed. A greenlocking scheme was employed to stabilize the polarization-circulation cavity, and a lock-acquisition procedure was demonstrated to realize speed-meter operation. The system was characterized by measuring the transfer function from a pseudodisplacement signal to the photodetector output, confirming that the device measures the speed of mirror motion. These results support the feasibility of polarization-circulation speed meters and suggest that the control scheme could be extended to more complex configurations, such as Michelson interferometers and suspended-mirror systems.