10.6 - Continuously variable laser acoustic delay line

A continuously variable delay of electromagnetic signals in the 10⁷to 10⁹Hz region is achieved through the interaction of a laser beam and an acoustic wave. Delays up to 10μs can be obtained in single-pass configurations while substantially longer delays are available in folded acoustic path configurations. Several novel optical-heterodyning techniques are employed to recover the delayed signal impressed on the laser beam. A theoretical study of the bandwidth limitations is presented along with several experimental verifications and a bandwidth measurement technique. Finally, the use of electronically controlled, optically scanned configurations to affect the variable delay is discussed.