Use of radio-frequency-pulse surface acoustic wave profilometry for passband engineering of acousto-optic tunable filters.

One can determine the acoustic profile of an acousto-optic tunable filter (AOTF) either by measuring the intensity of a laser diffracted off the surface of an AOTF by the surface acoustic wave (SAW) or by measuring the optical output power of an AOTF as a short burst of rf energy is launched down the device. This rf-burst technique (also called pulse probing) is compared with the established optical diffraction SAW profilometry technique. We demonstrate the usefulness of rf-burst profilometry to measure the acousto-optic coupling as a function of position along an AOTF interaction region. Such a probe can be used to make adjustments to the acousto-optic coupling in real time to achieve passband shape modification in complex AOTF structures.