AO deflectors can be used to scan a laser beam. This is achieved by changing the RF drive frequency. Random position, continuous line scans and sequential spot deflection are all possible. Scan rates in excess of 250KHz can be achieved depending on the crystal, wavelength and beam size.
Optimum efficiency requires that the input laser beam is set at the Bragg angle which is a function of the drive frequency. When swept to scan the laser beam there will be Bragg angle mismatch since the AOD can only be optically aligned at one drive frequency. In general this will cause a reduction in efficiency depending on the scan range. Several techniques may be used to minimize this effect:
- Off-axis AO deflectors (“OAD”) minimize the Bragg angle - frequency sensitivity by exploiting non-linear characteristics of birefringent crystals.
- Beam steered AO deflectors (“-BS”) electronically steer the acoustic column inside the crystal depending on the RF drive frequency. This requires a phased array electrode on the transducer with 2 or 4 RF inputs.
Chose desired wavelength range on left