Acousto-optical tunable filter and a laser tuned by it

摘要

The filter includes a base of birefringent acousto- optic material adapted to receive an incoming beam of light. A transducer is responsive to an electrical signal to induce an acoustic wave in the base. The acoustic wave is operable to change the polarisation mode of any light propagating through the base. The acoustic wave has a frequency within an optical frequency band defined by the frequency of the acoustic wave and the optical properties of the base but not to change the polarisation mode of any light having a frequency outside the optical frequency band. a control device is provided for controlling an optical property of the base by adjusting the birefringence of the acousto- optic material.