Laser Source Spatial Distribution Of Impact Studies On Laser Saw

The effects of laser spatical distribution and laser line source array on the spetrum of surface acoustic waves (SAWs) are studided theoretically in this paper.Based on theoretical model of SAWs excited by line source with finite length and infinite width ,the theorical model of SAWs excited by line source with finite width is established. By changing the laser pulse width and line source half-width, the effect of line source on SAWs is studied.The results show that as a result of the laser pulse width and line source half-width, the bandwidth of SAWs increases. For the case of fixed laser pulse width ,bandwidth of SAWs expands and its amplitude increases as the half-width of laser line source decreases. Under this condition,SAWs with higher limit frequency can be obtained.The line source half-width has a limit,the bandwidth of SAWs dosen't expand as the half-width decreases.The theoretical model of SAWs excited by laser line source array is established. At the same time, the waveforms and spectrum of SAWs excited by line source array are analized. The results show that the spectrum amplitude of SAWs excited by line source array increases obviously and broad-band signal changes into narrow bandwidth.The effect of spacing and number of line source on the spectrum os SAWs is discussed. The SAWs generated by line source detach form each other as the spacing of line source increases and the speed of envolope spectrum gradually slows down. Spectrum bandwidth of SAWs excited by line source array narrows gradually as the number of line source decreases.Based on the theoretical model of SAWs excited by line source array. The effect of line source array caused by mask on the surface of sample on the SAWs is studied. Changing the width of strip of mask,it influences the amplitude of spectrum of SAWs and the whole spectrum envelope while the half-width of spectrum doesn't change.Changing the distance between the strip,the frequency difference between separate peaks obviously changes.The frequency differences between separate peaks decrease as the central distance between the strips increases.So the spectrum distrubtion of SAWs can be controlled by changing the parameters of line source array.