Diode laser frequency control for cavity ring-down spectroscopy

We describe a system consisting of an extended cavity laser electronically locked to a high finesse cavity. The Pound-Drever-Hall technique is used, with the side-bands applied at 30 MHz, and a servo bandwidth of nearly 3 MHz. Repetitive locking and un-locking is accomplished by the use of high-speed analog switches at a number of positions in the feedback circuit.