UV reflective modulation using SAWs with high amplitude

Light beam diffraction at high amplitude surface acoustic waves generated on piezoelectrical crystals enables us to construct new optical devices. The first order diffraction efficiency increases with decreasing light wavelength and in the UV range it becomes considerably for available high amplitudes. The generation of SAWs sufficiently high displacement amplitudes normal to the surface remains the chief problem due to the related power. For minimising these problems we had to choose proper crystals, orientations and IDT constructions. Special experimental techniques have been introduced to study high acoustic power effects on the sample: damaging of electrodes using SEM, temperature profiles on the sample surface by thermography. In addition, for the calibrated measurement of SAW amplitudes as a function of input power, we developed a novel optical probing method using two single mode light fibres. UV diffraction efficiencies up to 9% have been obtained for a 38°rot.ZX-LiNbO₃ device corresponding to a SAW power of 10 W