Phase Pound – Drever-Hall Technique

The Pound-Drever-Hall (PDH) technique is an application of FM spectroscopy to detect the resonances of the optical cavity by demodulating the beam reflected from the cavity. The PDH technique is often part of a control system which regulates the frequency of a laser to match the resonance condition of a cavity. Phase modulated light, consisting of a carrier frequency and two side bands (well outside the FWHM of the cavity), is directed onto a two mirror cavity. Light reflected off the cavity is measured using a high speed photodetector, the reflected signal consists of the two unaltered side bands along with a phase shifted carrier component. This light is then measured using a photodetector and is mixed down with a phase shifted local oscillator and low pass filtered. The resulting electronic readout signal gives a measure of how far the laser carrier is off resonance with the cavity. Conoptics manufactures a complete line of Phase Modulators and Drivers to work with the PDH technique.

Phase Modulator Sensitivity

Model 200 Driver Specifications

Additional Information

• Notes on the Pound-Drever-Hall technique