Our CRDS setup uses a continuous diode laser to excite a bow-tie cavity. The animated image below demonstrates the steps in recording a ring-down transient. First, the laser is directed towards the cavity by the acousto-optic modulator (a fast optical switch). Then the energy builds up within the cavity until it a high level is detected leaking out the back mirror. At this point, the input laser is chopped, and the ring-down transient is observed.
